Ändra sökning
Avgränsa sökresultatet
1234567 1 - 50 av 314
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Adegoke, Olutayo
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Brodin, Håkan
    Materials Technology Additive Manufacturing Product Development-Industrial Gas Turbines, Siemens Industrial Turbomachinery, Finspång, SE-612 83, Sweden.
    Pederson, Robert
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Influence of laser powder bed fusion process parameters on voids, cracks, and microhardness of nickel-based superalloy alloy 247LC2020Ingår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 13, nr 17, artikel-id 3770Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The manufacturing of parts from nickel-based superalloy Alloy 247LC by laser powder bed fusion (L-PBF) is challenging, primarily owing to the alloy’s susceptibility to cracks. Apart from the cracks, voids created during the L-PBF process should also be minimized to produce dense parts. In this study, samples of Alloy 247LC were manufactured by L-PBF, several of which could be produced with voids and crack density close to zero. A statistical design of experiments was used to evaluate the influence of the process parameters, namely laser power, scanning speed, and hatch distance (inherent to the volumetric energy density) on void formation, crack density, and microhardness of the samples. The window of process parameters, in which minimum voids and/or cracks were present, was predicted. It was shown that the void content increased steeply at a volumetric energy density threshold below 81 J/mm3. The crack density, on the other hand, increased steeply at a volumetric energy density threshold above 163 J/mm3. The microhardness displayed a relatively low value in three samples which displayed the lowest volumetric energy density and highest void content. It was also observed that two samples, which displayed the highest volumetric energy density and crack density, demonstrated a relatively high microhardness; which could be a vital evidence in future investigations to determine the fundamental mechanism of cracking. The laser power was concluded to be the strongest and statistically most significant process parameter that influenced void formation and microhardness. The interaction of laser power and hatch distance was the strongest and most significant factor that influenced the crack density. © 2020 by the authors.

    Ladda ner fulltext (pdf)
    fulltext
  • 2.
    Adegoke, Olutayo
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Brodin, Håkan
    Siemens Industrial Turbomachinery, Finspång, 612 83, Sweden.
    Pederson, Robert
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Review of laser powder bed fusion of gamma-prime-strengthened nickel-based superalloys2020Ingår i: Metals, ISSN 2075-4701, Vol. 10, nr 8, artikel-id 996Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper reviews state of the art laser powder bed fusion (L-PBF) manufacturing of γ′ nickel-based superalloys. L-PBF resembles welding; therefore, weld-cracking mechanisms, such as solidification, liquation, strain age, and ductility-dip cracking, may occur during L-PBF manufacturing. Spherical pores and lack-of-fusion voids are other defects that may occur in γ′-strengthened nickel-based superalloys manufactured with L-PBF. There is a correlation between defect formation and the process parameters used in the L-PBF process. Prerequisites for solidification cracking include nonequilibrium solidification due to segregating elements, the presence of liquid film between cells, a wide critical temperature range, and the presence of thermal or residual stress. These prerequisites are present in L-PBF processes. The phases found in L-PBF-manufactured γ′-strengthened superalloys closely resemble those of the equivalent cast materials, where γ, γ′, and γ/γ′ eutectic and carbides are typically present in the microstructure. Additionally, the sizes of the γ′ particles are small in as-built L-PBF materials because of the high cooling rate. Furthermore, the creep performance of L-PBF-manufactured materials is inferior to that of cast material because of the presence of defects and the small grain size in the L-PBF materials; however, some vertically built L-PBF materials have demonstrated creep properties that are close to those of cast materials.© 2020 by the authors. Licensee MDPI, Basel, Switzerland.

    Ladda ner fulltext (pdf)
    fulltext
  • 3.
    Adegoke, Olutayo
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Brodin, Håkan
    Siemens Industrial Turbomachinery, 612 83, Finspång (SWE).
    Pederson, Robert
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Harlin, Peter
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT). Sandvik Additive Manufacturing, Sandviken (SWE).
    Influence of laser powder bed fusion process parameters on the microstructure and cracking susceptibility of nickel-based superalloy Alloy 247LC2022Ingår i: Results in Materials, ISSN 2590-048X, Vol. 13, artikel-id 100256Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Microstructures of material conditions of nickel-based superalloy Alloy 247LC fabricated using laser powder bed fusion (L-PBF) were investigated. Experiments designed in a prior study revealed the L-PBF process parameters for which the material conditions displayed a reduced susceptibility to cracking. Certain process parameters produced material conditions with an increased susceptibility to cracking. In this study, the material conditions were investigated in detail to reveal their microstructure and to determine the cause of cracking. The reason for the transition between a reduced to an increased susceptibility to cracking was examined. The results revealed solidification cracking occurred at high-angle grain boundaries. Solidification cracking may have been promoted at high-angle grain boundaries because of the undercooling contribution of the grain boundary energy. Furthermore, Si segregation was observed in the cracks. Thus, the presence of Si most likely promoted solidification cracking. It was observed that a high crack density, which occurred in the high energy density material condition, was associated with a large average grain size. The fact that certain combination of process parameters produced microstructures with a low susceptibility to cracking, indicates that reliable Alloy 247LC material may be printed using L-PBF by employing improved process parameters. © 2022

    Ladda ner fulltext (pdf)
    fulltext
  • 4.
    Adegoke, Olutayo
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Ojo, Olanrewaju A.
    University of Manitoba, Winnipeg, Canada.
    Brodin, Håkan
    Siemens Industrial Turbomachinery AB, Finspang, Sweden .
    Pederson, Robert
    GKN Aerospace, Redditch, United Kingdom.
    Laser beam powder bed fusion and post processing of alloy 247LC2019Ingår i: MS and T 2019 - Materials Science and Technology, Materials Science and Technology , 2019, s. 27-34Konferensbidrag (Refereegranskat)
    Abstract [en]

    Alloy 247LC is sensitive to cracking during laser beam powder bed fusion (PBF-LB) manufacturing. Post processing is thus required to close cracks and achieve desired properties. In this study, samples of Alloy 247LC were manufactured by PBF-LB and subsequently post processed by hot isostatic pressing (HIP), HIP + solution and ageing heat treatments. The microstructure was characterized. Results showed cracks in the as-built condition. Cracks were not detected after HIP. Bright microconstituents were observed in the region between the cells, mainly, because of the partitioning of Hf and Ta into the intercellular region, where they presumably form carbides. What is assumed to be oxides were prominent in the microstructure. Thermodynamic calculations showed rapid formation of ?’ precipitates in the alloy, due to the high total concentration of Al and Ta and this was linked to the high hardness values in the as-built condition. © 2019 MS&T19®

  • 5.
    Adegoke, Olutayo
    et al.
    Siemens Energy, Finspång (SWE).
    Kumara, Chamara
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT). FEV Sverige AB, Trollhättan (SWE).
    Thuvander, Matttias
    Department of Physics, Chalmers University of Technology, Gothenburg (SWE).
    Deirmina, Faraz
    Siemens Energy, Finspång (SWE).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Brodin, Håkan
    Siemens Energy, Finspång (SWE).
    Harlin, Peter
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT). Sandvik Additive Manufacturing, Sandviken (SWE).
    Pederson, Robert
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Scanning electron microscopy and atom probe tomography characterization of laser powder bed fusion precipitation strengthening nickel-based superalloy2023Ingår i: Micron, ISSN 0968-4328, E-ISSN 1878-4291, Vol. 171, artikel-id 103472Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Atom probe tomography (APT) was utilized to supplement scanning electron microscopy (SEM) characterizationof a precipitation strengthening nickel-based superalloy, Alloy 247LC, processed by laser powder bed fusion (LPBF). It was observed that the material in the as-built condition had a relatively high strength. Using both SEMand APT, it was concluded that the high strength was not attributed to the typical precipitation strengtheningeffect of γ’. In the absence of γ’ it could be reasonably inferred that the numerous black dots observed in thecells/grains with SEM were dislocations and as such should be contributing significantly to the strengthening.Thus, the current investigation demonstrated that relatively high strengthening can be attained in L-PBF even inthe absence of precipitated γ’. Even though γ’ was not precipitated, the APT analysis displayed a nanometer scalepartitioning of Cr that could be contributing to the strengthening. After heat-treatment, γ’ was precipitated and itdemonstrated the expected high strengthening behavior. Al, Ta and Ti partitioned to γ’. The strong partitioningof Ta in γ’ is indicative that the element, together with Al and Ti, was contributing to the strain-age crackingoccurring during heat-treatment. Cr, Mo and Co partitioned to the matrix γ phase. Hf, Ta, Ti and W were found inthe carbides corroborating previous reports that they are MC. 

  • 6.
    Adegoke, Olutayo
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Polisetti, Satyanarayana Rao
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Xu, Jinghao
    Linköpings universitet, Linköping.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Brodin, Håkan
    Siemens Industrial Turbomachinery, Finspång.
    Pederson, Robert
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Harlin, Peter
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT). Sandvik Additive Manufacturing, Sandviken.
    Influence of laser powder bed fusion process parameters on the microstructure of solution heat-treated nickel-based superalloy Alloy 247LC2022Ingår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 183, artikel-id 111612Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, Alloy 247LC samples were built with different laser powder bed fusion (L-PBF) process parameters. The samples were then subjected to solution heat treatment at 1260 °C for 2 h. The grain size of all the samples increased significantly after the heat treatment. The relationship between the process parameters and grain size of the samples was investigated by performing a design of experiment analysis. The results indicated that the laser power was the most significant process parameter that influenced the grain height and aspect ratio. The laser power also significantly influenced the grain width. The as-built and as-built + heat-treated samples with high, medium, and low energy densities were characterized using a field emission gun scanning electron microscope equipped with an electron backscatter diffraction detector. The micrographs revealed that the cells present in the as-built samples disappeared after the heat treatment. Isolated cases of twinning were observed in the grains of the as-built + heat-treated samples. The disappearance of cells, increase in the grain size, and appearance of twins suggested that recrystallization occurred in the alloy after the heat treatment. The occurrence of recrystallization was confirmed by analyzing the grain orientation spread of the alloy, which was lower and more predominantly <1° in the as-built + heat-treated conditions than in the as-built conditions. The microhardness of the as-built + heat-treated samples were high which was plausible because γ’ precipitates were observed in the samples. However, the L-PBF process parameters had a very low correlation with the microhardness of the as-built + heat-treated samples.

    Ladda ner fulltext (pdf)
    fulltext
  • 7.
    Agili, Uchechukwu Daniel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Numerical Simulation of Aluminium Butt-weld2020Självständigt arbete på avancerad nivå (magisterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The aim of this study was to investigate the effect of the welding heat input on the heat affected zone (HAZ)in AA6005-T6 aluminium alloy for a butt-welded joint using gas metal arc welding by evaluating the thermal cycles, metallography and the resulting mechanical properties in the zone. This study involved using a welding experiment, numerical simulation, physical simulation and mechanical tests. The welding was carried out using the pulsed gas metal arc welding (GMAW) transfer and type J thermocouples were used to get the thermal cycles in the HAZ. Simufact® Welding was utilised for the numerical simulation. Optical microscope was used to evaluate the microstructures and Vickers microhardness test was done along the weld cross-section. The thermal cycles of thealuminium alloy and a thermal model for the experimental setup was developed. The HAZ was located on the weld cross-section with a mean hardness of 63.7HV0.1, which is considerably lower when compared with the base metal which has a hardness of 100HV0.1. This indicates thermal softening occurred due to the heat input to the material. There is a match in the hardness values of the Gleeble samples and the locations on the weld cross section suggested by the model showing validity of the simulation. This thesis work isused to assess the implications of heat input in aluminium weld joints, identify the HAZ and its mechanical properties in the design of welding process parameters for automobile parts. The Welding parameters can be optimized to reduce the amount of heat input into the weld as this will directly affect the mechanical properties int he HAZ.

  • 8.
    Ahmadpour, Ali
    et al.
    Amirkabir University of Technology, Department of Mechanical Engineering, Tehran, Iran.
    Noori Rahim Abadi, Seyyed Mohammad Ali
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Thermal-hydraulic performance evaluation of gas-liquid multiphase flows in a vertical sinusoidal wavy channel in the presence/absence of phase change2019Ingår i: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 138, s. 677-689Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Turbulent gas-liquid multiphase flows with and without phase change in a vertical wavy channel are addressed. The multiphase flow field is resolved using the volume of fluid method (VOF), and the flow equations are discretized and numerically solved by the well-known finite volume method. As a multiphase system without mass transfer, air/water flow is considered. It is shown that numerical simulation is well capable of predicting the various multiphase flow regimes ranging from slug to bubbly flows inside wavy channels. Moreover, accurate predictions of overall pressure drop are provided by numerical solutions for various air and water flow rates and the phase shift angle between wavy channel walls. Additionally, condensing flows of refrigerant R134a are simulated inside wavy channels. It is found that for almost all the cases considered in the present study, the convective heat transfer coefficient is higher in wavy channels in respect to straight channels. However, a significant pressure drop penalty is observed especially for high mass fluxes across wavy channels. Therefore, the use of the wavy channels for the enhancement of condensing heat transfer is only advisable for low mass fluxes with the phase shift angle of 180°. © 2019 Elsevier Ltd

  • 9.
    Amouzgar, Kaveh
    et al.
    University of Skovde, Jonkoping University.
    Strömberg, Niclas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Jonkoping University, Orebro Univ, University University West - Sweden.
    An approach towards generating surrogate models by using RBFN with a priori bias2014Ingår i: PROCEEDINGS OF THE ASME INTERNATIONAL DESIGN ENGINEERING TECHNICAL CONFERENCES AND COMPUTERS AND INFORMATION IN ENGINEERING CONFERENCE, 2014, VOL 2B, AMER SOC MECHANICAL ENGINEERS , 2014, Vol. 2BKonferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, an approach to generate surrogate models constructed by radial basis function networks (RBFN) with a priori bias is presented. RBFN as a weighted combination of radial basis functions only, might become singular and no interpolation is found. The standard approach to avoid this is to add a polynomial bias, where the bias is defined by imposing orthogonality conditions between the weights of the radial basis functions and the polynomial basis functions. Here, in the proposed a priori approach, the regression coefficients of the polynomial bias are simply calculated by using the normal equation without any need of the extra orthogonality prerequisite. In addition to the simplicity of this approach, the method has also proven to predict the actual functions more accurately compared to the RBFN with a posteriori bias. Several test functions, including Rosenbrock, Branin-Hoo, Goldstein-Price functions and two mathematical functions (one large scale), are used to evaluate the performance of the proposed method by conducting a comparison study and error analysis between the RBFN with a priori and a posteriori known biases. Furthermore, the aforementioned approaches are applied to an engineering design problem, that is modeling of the material properties of a three phase spherical graphite iron (SGI). The corresponding surrogate models are presented and compared.

  • 10.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Fabrication and Weldability Aspects of Ni- and Ni–Fe Based Superalloys: A Review2023Ingår i: Proceedings of the 10th International Symposium on Superalloy 718 and Derivatives / [ed] Eric A. Ott, Joel Andersson, Chantal Sudbrack, Zhongnan Bi, Kevin Bockenstedt, Ian Dempster, Michael Fahrmann, Paul Jablonski, Michael Kirka, Xingbo Liu, Daisuke Nagahama, Tim Smith, Martin Stockinger, Andrew Wessman, Springer Cham , 2023, s. 659-696Konferensbidrag (Refereegranskat)
    Abstract [en]

    Superalloys are commonly used in structural components of aero-engines. Superalloys in general, Ni- and Ni–Fe-based superalloys, belong to an important group of materials used in aerospace applications. Fabrication and associated weldability aspects of structural components for the hot section of aero-engine gas turbines continue to be of high importance to the manufacturing industry within this discipline. Cracking and specifically hot cracking as well as strain age cracking is a serious concern during the welding and additive manufacturing (AM) of these structural components. The cracking phenomena can occur during welding, AM or subsequent heat treatment of precipitation-hardening superalloys. The cracking behaviour can be influenced by several factors, i.e., chemical composition in terms of hardening elements and impurities, the microstructure of base material, and weld zone, together with corresponding welding, AM and post-treatment process parameters. This paper provides a review of Ni- and Ni–Fe-based superalloys concerning fabrication and weldability aspects within the context of structural components of aero-engines. Also, the paper offers insight and analyses to research publication data of welding and AM of superalloys in the context of annual publication developed over the years as well as specific contributions from countries, affiliations, and specific researchers.

  • 11.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Review of Weldability of Precipitation Hardening Ni- and Fe-Ni-Based Superalloys2018Ingår i: Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives: Energy, Aerospace, and Industrial Applications / [ed] Ott, E., Liu, X., Andersson, J., Bi, Z., Bockenstedt, K., Dempster, I., Groh, J., Heck, K., Jablonski, P., Kaplan, M., Nagahama, D. and Sudbrack, C., Springer, 2018, s. 899-916Konferensbidrag (Refereegranskat)
    Abstract [en]

    Fabrication and welding of structural components for the hot section of aero-engines continues to be of high importance to the manufacturing industry of aero-engines. This paper discusses and reviews the literature on hot cracking and strain age cracking, cracking phenomena that can occur during welding or subsequent heat treatment of precipitation hardened Ni- and Fe-Ni-based superalloys. The influence of chemical composition in terms of i.e. hardening elements and impurities, microstructure of base material and weld zone, together with welding processes and corresponding parameters and heat input are discussed and related to the cracking susceptibility of different nickel based superalloys.

  • 12.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Welding metallurgy and weldability of superalloys2020Ingår i: Metals, ISSN 2075-4701, Vol. 10, nr 1, artikel-id 143Artikel i tidskrift (Refereegranskat)
    Ladda ner fulltext (pdf)
    fulltext
  • 13.
    Andersson, Joel
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Hosseini, Vahid
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Neikter, Magnus
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Pederson, Robert
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Welding of special alloys2023Ingår i: Welding of Metallic Materials: Methods, Metallurgy, and Performance / [ed] Fuad Khoshnaw, Elsevier , 2023, s. 279-316Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    Specialty alloys are a broad group of materials providing superior properties to common materials and are therefore used for more demanding applications. Specialty alloys require sophisticated manufacturing routes, e.g., vacuum metallurgy, to account for all the alloying elements needed to finalize the specific alloy for its intended purpose. The alloys of Duplex stainless steels, superalloys, and Titanium alloys are examples of so-called specialty alloys where aerospace, chemical, and petrochemical industries are just a few areas mentioned where these specialty alloys are frequently used. Duplex stainless steel, had superior mechanical properties and corrosion resistance, making them a sustainable choice for a wide variety of applications i.e., petrochemical industries. The superalloys, and especially the precipitation hardening ones belong to a unique plethora of alloys commonly used in aerospace as well as land-based gas turbines which possess superb mechanical performance at elevated temperatures. However, the superalloys are unfortunately very challenging to process, not at least regarding weld cracking. With their high specific strength and corrosion resistance, titanium alloys are favorable for numerous applications. However, they react readily with oxygen at elevated temperatures and therefore inert atmosphere must be used during welding. 

  • 14.
    Andersson, Joel
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Joshi, Shrikant V.Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).Malmsköld, LennartHögskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).Hanning, FabianHögskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Sustainable Production through Advanced Manufacturing, Intelligent Automation and Work Integrated Learning: Proceedings of the 11th Swedish Production Symposium (SPS2024)2024Proceedings (redaktörskap) (Refereegranskat)
    Abstract [en]

    Collaboration between those working in product development and production is essential for successful product realization. The Swedish Production Academy (SPA) was founded in 2006 with the aim of driving and developing production research and higher education in Sweden, and increasing national cooperation in research and education within the area of production.

    This book presents the proceedings of SPS2024, the 11th Swedish Production Symposium, held from 23 to 26 April 2024 in Trollhättan, Sweden. The conference provided a platform for SPA members, as well as for professionals from industry and academia interested in production research and education from around the world, to share insights and ideas. The title and overarching theme of SPS2024 was Sustainable Production through Advanced Manufacturing, Intelligent Automation and Work Integrated Learning, and the conference emphasized stakeholder value, the societal role of industry, worker wellbeing, and environmental sustainability, in alignment with the European Commission's vision for the future of manufacturing. The 59 papers included here were accepted for publication and presentation at the symposium after a thorough review process. They are divided into 6 sections reflecting the thematic areas of the conference, which were: sustainable manufacturing, smart production and automation, digitalization for efficient product realization, circular production, industrial transformation for sustainability, and the integration of education and research.

    Highlighting the latest developments and advances in automation and sustainable production, the book will be of interest to all those working in the field.

    Ladda ner fulltext (pdf)
    Bokens fulltext
  • 15.
    Ariaseta, Achmad
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Department of Metallurgical Engineering, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132 (IDN).
    Khan, Abdul Khaliq
    Manitoba Institute for Materials, University of Manitoba, Winnipeg (CAN).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Ojo, Olanrewaju
    Department of Mechanical Engineering, University of Manitoba, Winnipeg (CAN).
    Microstructural study of keyhole TIG welded nickel-based superalloy G272023Ingår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 204, artikel-id 113178Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The weld fusion zone (FZ) microstructure obtained after keyhole tungsten inert gas welding and post-weld solution heat treatments (PWSHTs) of a new nickel (Ni)-based superalloy called G27 is studied, and the grain growth behavior in the base material (BM) during PWSHTs is characterized. Microsegregation-induced interdendritic microconstituents in the FZ of as-welded G27 are identified by analytical (scanning) transmission electron microscopy ((S)TEM) as niobium (Nb)-rich MC carbides, Nb-rich Laves eutectic constituents, γ’ and η phases. The Laves eutectics are generally considered brittle and can adversely affect the mechanical properties of the weldment; thus, an hour PWSHTs were performed at 954 °C–1060 °C to eliminate the γ/Laves eutectics. PWSHT up to 1010 °C results in only partial removal of Laves eutectics with an excessive formation of η phase surrounding the Laves phase. Complete dissolution of Laves eutectics with no η phase formation is achieved after a PWSHT is performed at 1060 °C. Relative to INCONEL® alloy 718, the complete elimination of the γ/Laves eutectic constituents in the FZ of G27 through a PWSHT was proven to be achieved without causing excessive grain growth in the BM, which could be due to the pinning effect of the fine molybdenum (Mo)-rich precipitates, that are formed during solution heat treatment and identified as hexagonal close-packed phase particles through extensive (S)TEM analyses.

    Ladda ner fulltext (pdf)
    fulltext
  • 16.
    Ariaseta, Achmad
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Pick, Dario
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Ojo, Olanrewaju
    Department of Mechanical Engineering, University of Manitoba, Winnipeg (CAN).
    Keyhole TIG Welding of New Co-Lean Nickel-Based Superalloy G272023Ingår i: Proceedings of the 10th International Symposium on Superalloy 718 and Derivatives / [ed] Eric A. Ott, Joel Andersson, Chantal Sudbrack, Zhongnan Bi, Kevin Bockenstedt, Ian Dempster, Michael Fahrmann, Paul Jablonski, Michael Kirka, Xingbo Liu, Daisuke Nagahama, Tim Smith, Martin Stockinger, Andrew Wessman, Springer Cham , 2023, s. 807-824Konferensbidrag (Refereegranskat)
    Abstract [en]

    The influence of keyhole TIG (K-TIG) welding parameters on the weld geometry and defects of a new Co-lean nickel-based superalloy G27 was studied, and the microstructures of the heat-affected zone (HAZ) and fusion zone (FZ) of the K-TIG-welded Alloy G27 were characterized. No cracks are found in the FZ and HAZ. Minimum weld width and face underfill statistically were significantly influenced by travel speed and interaction current*travel speed. Root excess weld metal was only significantly influenced by travel speed. Face excess weld metal was significantly influenced by all the factors, including their interaction. On the other hand, all the factors, including their interaction, did not significantly influence the average pore diameter. In the FZ microstructure, interdendritic microconstituents are identified as (Nb, Ti)C particles and γ/Laves eutectic constituents. In addition, a plate-like phase is observed surrounding the Laves phase, and γʹ precipitates are found to be inhomogeneously precipitated in the FZ. In the partially melted zone (PMZ), (Nb, Ti)C, Laves phase, γʹ precipitates, and plate-like particles are found in the liquated and resolidified regions, suggesting the solidification behavior in PMZ is likely to follow a similar pattern to the one observed in FZ.

  • 17.
    Ariaseta, Achmad
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Department of Metallurgical Engineering, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132 (IDN).
    Pick, Dario
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Ojo, Olanrewaju
    Department of Mechanical Engineering, University of Manitoba, Winnipeg, MB R3T 5V6 (CAN).
    Study of Pulsed Laser Beam Welding of Nickel-Based Superalloy G272024Ingår i: Sustainable Production through Advanced Manufacturing, Intelligent Automation and Work Integrated Learning: Proceedings of the 11th Swedish Production Symposium (SPS2024) / [ed] Joel Andersson, Shrikant Joshi, Lennart Malmsköld, Fabian Hanning, IOS Press , 2024, s. 39-49Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    The influence of pulsed laser beam welding (LBW) parameters on the weld geometry and imperfections of a new nickel-based superalloy called G27 was studied by a statistical design of experiment, and the microstructures of the weld fusion zone (FZ) of the pulsed laser beam-welded G27 were characterized. No evidence of cracks is found in the FZ and heat-affected zone (HAZ). Other weld imperfections, such as undercut and underfill, were also hardly observed.

    The pulse factor significantly influenced all the responses, i.e., minimum weld width (Wm), root excess weld metal, and average pore diameter, whereas welding travel speed significantly influenced Wm and root excess weld metal. Power and interaction between pulse frequency*pulse factor were statistically significant in influencing the root excess weld metal and average pore diameter, respectively. The pulse frequency and interactions between power*travel speed, power*pulse factor, power*pulse frequency, travel speed*pulse factor, and travel speed*pulse frequency did not significantly influence any response.

    Microsegregation pattern that occurs during weld solidification leads to the formation of Nb-rich MC carbides and Nb-rich Laves phase as the major secondary phase constituents in the FZ of as-welded G27. The presence of brittle Laves phase requires careful consideration when developing suitable post-weld heat treatment of G27.

    Ladda ner fulltext (pdf)
    fulltext
  • 18.
    Ariaseta, Achmad
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Department of Metallurgical Engineering, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132, (IDN)).
    Sadeghinia, Nima
    Högskolan Väst, Institutionen för ingenjörsvetenskap.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Influence Of Keyhole Tig Welding Parameters On Weld Geometry Of Newly-Developed Superalloy Vdm Alloy 7802022Ingår i: ICAS PROCEEDINGS33th Congress of the International Council of the Aeronautical SciencesStockholm, Sweden, 2022, Vol. 5, s. 3516-3530Konferensbidrag (Refereegranskat)
    Abstract [en]

    The welding process and the associated control, to a certain degree, have enhanced remarkably in the last decades. One of the recent processes is keyhole TIG (K-TIG) welding, which allows better control and the capability to use lower heat input and higher power density during the welding compared to the conventional one, being essential when joining sophisticated materials utilized in the hot sections of aircraft engines such as nickel-based superalloys. The recent trend in the fabrication of hot sections of aero-engines has been preferably carried out by joining small pieces of superalloys by the welding process instead of casting a single large component due to several benefits, such as lowering the total weight of the components and improving the design flexibility. VDM Alloy 780, a new polycrystalline nickel-based superalloy with service temperature capabilities up to 750 °C, is a promising material to be employed in the fabrication of hot structural parts of an aero-engine. For aerospace manufacturers, producing a superalloy weld bead geometry that meets stringent quality requirements for aerospace applications is crucial. To do so, understanding the influence of welding parameters on weld geometry becomes indispensable, especially when welding a new superalloy using a relatively new welding technique. Hence, in this article, the influence of K-TIG welding parameters on the weld geometry of VDM Alloy 780 has been investigated.

    Ladda ner fulltext (pdf)
    fulltext
  • 19.
    Ariaseta, Achmad
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Department of Metallurgical Engineering, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung (IDN).
    Sadeghinia, Nima
    Högskolan Väst, Institutionen för ingenjörsvetenskap.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Ojo, Olanrewaju
    Department of Mechanical Engineering, University of Manitoba, Winnipeg (CAN).
    Keyhole TIG welding of newly developed nickel-based superalloy VDM Alloy 7802023Ingår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 67, nr 1, s. 209-222Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of keyhole TIG (K-TIG) welding parameters on the weld geometry and defects of a new nickel-based superalloy VDM Alloy 780 alloy were investigated using a statistical design of experiment, and the microstructures of the heat-affected zone (HAZ) and fusion zone (FZ) of the K-TIG-welded VDM Alloy 780 were characterized. No cracks are found in the FZ and HAZ. Travel speed significantly influences the minimum weld width (Wm), face and root excess weld metal, face underfill, and average pore diameter. Welding current and the interaction current*travel speed significantly influence the face and root excess weld metals, respectively. Interdendritic microconstituents in the FZ are identified as (Nb,Ti)C particles and γ/Laves eutectic constituents based on SEM–EDS analysis. In addition, plate-like precipitates likely to be δ/η phase are observed surrounding the interdendritic Laves eutectics, and γ′ precipitates are found to be inhomogeneously precipitated in the FZ. In the partially melted zone (PMZ), (Nb,Ti)C, Laves phase, and plate-like particles are found in the liquated and resolidified regions. Constitutional liquation of (Nb,Ti)C in HAZ is observed where the liquated (Nb,Ti)C appears to be associated with the γ/Laves eutectic as a resolidified product. 

    Ladda ner fulltext (pdf)
    fulltext
  • 20.
    Aryal, Pradip
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Gas Metal Arc Melt Pool Modelling: Effect of welding position and electromagnetic force mode2021Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Gasmetallbåge är en effektiv och allmänt använd värmekälla vid svetsning och additiv tillverkning. I denna studie tillämpas den på svetsning. Den erbjuder hög produktivitet, låg kostnad vid inköp och användning, såväl som vissa nackdelarsom ojämn "bucklig" svetssträng och smältdiken vid svetsning av stora komponenter som är krökta och medför att svetsbrännarens orientering ändras utmed fogen. Bättre processförståelse eftersträvas därför för att mildra dessa nackdelar. En utmaning är processens icke-linjära beroende av svetsparametrarna och materialegenskaperna. Dessutom är experimentell optisk övervakning svår. Till exempel kan den höga temperaturen och den intensiva elektromagnetiska strålningen från ljusbågen, rök, sprut, såväl som legeringens ogenomskinlighet, förhindra observation under processen eller begränsa den. Processimulering erbjuder en komplementär metod för att nå processkunskap. Det är alltså detta tillvägagångssätt som används i denna studie. För detta har en modell av värme och materialflödena i smältan utvecklats som kan prediktera smältning och stelning, spåra smältytans deformation, metallflöde och koalescens med smältan.Två huvudsakliga forskningsfrågor har identifierats och adresserats.

    Den första studerade gravitationens påverkan vid flersträngs-, gasmetallbågsvetsning av V-fogar i INVAR. Olika svetslägen har visat sig ha en betydande påverkan på kraftbalanserna i svetssmältan vilket resulterar i distinkta smältflöden, smält- och svetsförbandgeometrier, och under vissa förhållanden svetsdefekter såsom ojämn "bucklig" svetssträng, smältdiken och bindfel. Som ett resultat rekommenderas horisontellt och 20◦ fallande läge vid flersträngssvetsning, medan 20◦ stigande och sidolutande inte rekommenderas.

    Den andra frågan undersökte inverkan av de tre huvudsakliga modellerna för den elektromagnetiska kraften som idag används vid svetssimuleringar. För modelleringen har antaganden lagts fram och undersökts. Det visade sig att de tre modellerna predikterar olika flödesmönster i smältan, olika värmekonvektion, smältgeometri, ytvågor och interaktion med de överförda metalldropparna, och därmed också predikterar olika svetsstränggeometrier. Alla tre modeller kan justeras för att prediktera svetspenetrationen, men endast den mest kompletta av dessa rekommenderas för sant prediktiv modellering. Det föreslås också att ytterligare förbättra den mest kompletta modellen så att det elektromagnetiska kraftfältet följer deformationen av den fria smältytan.

    Ladda ner fulltext (pdf)
    fulltext
  • 21.
    Aryal, Pradip
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Metal fusion using pulsed GasMetal Arc: Melt pool modellingand CFD simulation2023Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Gasmetallbågsprocessen har revolutionerat metallbearbetning och produktionsteknik under ett århundrade med sin påfallande effektivitet och mångsidighet, speciellt vid svetsning. På senare år har denna teknik också tillämpats alltmer inom additiv tillverkning (AM), även känt som 3D-printing. Gasmetallbågsbaserad AM har väckt ett stort industriellt intresse på grund av dess förmåga att tillverka stora och komplexa komponenter. Det finns dock problem, dels kring defekter i processen, dels kring numeriska modellers förmåga att simulera processen. Följaktligen finns det ett behov av en djupare förståelse och förbättrade modeller för att övervinna dessa utmaningar och frigöra den fulla potentialen i denna teknologi. För att angripa detta problem utvecklades och tillämpades modellering med hjälp strömningsmekaniska beräkningar (CFD) i detta avhandlingsarbete, tillsammans med fysiska experiment för att komplettera modelleringsarbetet. Det utförda modelleringsarbetet har gjort det möjligt att förklara hur flödet i smältan och dess geometri orsakar defekter vid ändringar av ett arbetsstyckesorientering så lite som 20◦ jämfört med horisontell positionering vid svets iV-fog. Dessutom använder moderna numeriska modeller för smältans fysikolika delmodeller för att beräkna den elektromagnetiska kraften och tidsberoendet hos en pulserande ljusbåge. Dessa delmodeller jämförandes i en analys föratt förklara deras signifikanta skillnader vid simulering av smältflödet, termisk konvektion, ytvågor, smältans form och stelnade geometri. De föreslagna förbättringarna i modelleringen baserat på denna analys har gett mer noggranna förutsägelser av processens smältzon, vilket bidrar till utvecklingen av en sant prediktiv simuleringsmodell som kommer att vara användbar i den efterfrågade utvecklingen av gasmetallbågsprocessen.

    Ladda ner fulltext (pdf)
    Avhandlingen
    Ladda ner (pdf)
    Spikbladet
  • 22.
    Aryal, Pradip
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Choquet, Isabelle
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Melt pool electromagnetic force model extended to account for free surface deformation: Application to gas metal arc2024Ingår i: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 221, s. 124987-124987, artikel-id 124987Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Computational fluid dynamics models with free surface tracking intended to simulate the melt pool produced by an electric arc usually model the electromagnetic force ignoring the deformation of the free surface. However, with an arc heat source, the electromagnetic force is known to be among the leading-order forces, especially at high currents. In addition, the free surface can undergo significant deformations, especially in the presence of metal transfer. In the present study, a generalization of the electromagnetic force model that accounts for the deformation of the free surface is therefore proposed. Test cases with a pulsed gas-metal arc that transfers one metal drop per pulse were investigated experimentally at three different travel speeds to provide validation data. The cases were simulated with both the proposed and the earlier model to assess the influence of the new developments. The results showed that, in the regions where both models determine the force, the discrepancy between the models’ results can reach up to an order of magnitude. Especially, the earlier model overestimates the electromagnetic force deep into the melt pool. On the other hand, it neglects it in the liquid metal that is located at an elevation above the original upper surface of the workpiece, while the proposed model showed that in this area the intensity of the electromagnetic force is the largest. These significant discrepancies result in non-negligible differences in the predicted melt pool thermal flow and geometry. Especially, the propose dextended model provides an improved prediction of the fingertip-shaped fusion boundary.

    Ladda ner fulltext (pdf)
    fulltext
  • 23.
    Aryal, Pradip
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Sikström, Fredrik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Nilsson, Håkan
    Chalmers University of Technology Mechanics and Maritime Sciences, Fluid Dynamics, SE-412 96 Gothenburg, (SWE).
    Choquet, Isabelle
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Effect of Substrate Orientation on Melt Pool during Multi-Layer Deposition in V-Groove with Gas Metal Arc2021Ingår i: Proceedings of the 7th World Congress on Mechanical, Chemical, and Material Engineering (MCM'21) / [ed] Huihe Qiu, 2021, artikel-id HTFF 130Konferensbidrag (Refereegranskat)
    Abstract [en]

    Thermo-fluid dynamic and experimental approaches are used to investigate the influence of 20° uphill, downhill and sideway substrate orientation during metal deposition over a previously deposited bead in a V-groove. The computational fluid dynamic model with free surface deformation and metal transfer gives insight into the melt pool flow and causes of defect formation observed on the solidified beads. The experimental metallographs, high-speed images and computational results show good agreement. It is found that the deposition of a second layer on a smooth first layer cooled down to room temperature leads to large changes in melt pool flow patternat 20° substrate inclination compared to flat condition. It results in undercut and humps with the uphill orientation and undercut with the side inclination. Therefore, lower angle range is necessary for multilayer gas metal arc deposition for these two last configurations.

  • 24.
    Aryal, Pradip
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Sikström, Fredrik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Nilsson, H.
    Department of Mechanics and Maritime Sciences, Chalmers University of Technology, Gothenburg.
    Choquet, Isabelle
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Comparative study of the main electromagnetic models applied to melt pool prediction with gas metal arc: Effect on flow, ripples from drop impact, and geometry2022Ingår i: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 194, artikel-id 123068Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present work concerns the electromagnetic force models in computational fluid dynamics simulations of melt pools produced with electric arcs. These are commonly applied to gas metal arcs with metal transfer, in welding and additive manufacturing. Metal drop impact on the melt pool is thus included in this study. The electromagnetic force models applied in literature use either numerical solutions of Poisson equations or one of the two analytical models developed by Kou and Sun, or Tsao and Wu. These models rely on assumptions for which the effect on the melt pool predictions remains to be understood. The present work thoroughly investigates those assumptions and their effects. It has been supported by dedicated experimental tests that did provide estimates of unknown model parameters and validation data. The obtained results show that the assumptions that fundamentally distinguish these three models change the electromagnetic force, including the relation between its components. These changes, which can also be spatially non-uniform, are large. As a result, these models lead to significantly different recirculation flow pattern, thermal convection, melt pool morphology, bead dimensions, and free surface response to the metal transfer. We conclude by proposing conditions in which each of these models is suited or questionable.

  • 25.
    Asala, G.
    et al.
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, Canada.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Ojo, Olanrewaju
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, Canada.
    Microstructure Dependence of Dynamic Impact Behaviour of ATI 718plus® Superalloy2018Ingår i: Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives: Energy, Aerospace, and Industrial Applications / [ed] Ott, E., Liu, X., Andersson, J., Bi, Z., Bockenstedt, K., Dempster, I., Groh, J., Heck, K., Jablonski, P., Kaplan, M., Nagahama, D. and Sudbrack, C., Springer, 2018, s. 369-378Konferensbidrag (Refereegranskat)
    Abstract [en]

    ATI 718Plus® is a γ′-strengthened nickel-based superalloy developed to substitute the widely used Alloy 718 in aero-engine applications. This newer superalloy is a candidate material for aero-engine turbine structures, with the requirement to withstand impact loading occurring at high strain rates during turbine blade out events. Furthermore, the understanding of the high strain rate response of ATI 718Plus® is important in optimising its machinability during cutting operations. To predict and model the behaviour of ATI 718Plus® during these events and in other dynamic impact applications, proper understanding of the high strain rate behaviour of the alloy is important, but not presently available. Therefore, in this work, the influence of microstructural condition and strain rates on dynamic impact behaviour of ATI 718Plus®, using a modified version of direct impact Hopkinson bar, is investigated. It is observed that the age-hardened alloy exhibits a significantly reduced strain hardening and strain rate hardening capabilities compared to the solution heat treated microstructure. Furthermore, microstructural examination of the deformed samples shows that the formation of adiabatic shear bands, which usually serve as damage nucleation site, is substantially suppressed in the solution heat treated microstructure, while the aged microstructure exhibits high propensity to form localised shear bands.

  • 26.
    Asala, G.
    et al.
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, Canada.
    Khan, A. K.
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, Canada.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik. Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Ojo, O. A.
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, Canada.
    Microstructural Analyses of ATI 718Plus® Produced by Wire-ARC Additive Manufacturing Process2017Ingår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 48A, nr 9, s. 4211-4228Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A detailed microstructural study of ATI 718Plus superalloy produced by the wire-arc additive manufacturing (WAAM) process was performed through the use of scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron probe micro-analysis (EPMA), and electron backscatter diffraction (EBSD). Extensive formation of eutectic solidification microconstituents including Laves and MC-type carbide phases, induced by micro-segregation, are observed in the build of the alloy in the as-deposited condition. Notwithstanding the significant segregation of niobium (Nb), which has been reported to promote the formation of the delta-phase in ATI 718Plus, only eta-phase particles are observed in the deposit. Excessive precipitation of eta-phase particles is found to be linked to Laves phase particles that are partially dissolved in the deposit after post-deposition heat treatment (PDHT). The EBSD analysis shows a high textured build in the aOE (c) 100 > directions with only a few misoriented grains at the substrate-deposit boundary and the top of the deposit. Investigation on the hardness of the build of the alloy, in the as-deposited condition, showed a softened zone about 2 mm wide at the deposited metal heat affected zone (DMHAZ), which has not been previously reported and potentially damaging to the mechanical properties. An extensive analysis with the use of both microstructural characterization tools and theoretical calculations shows that the DMHAZ has the lowest volume fraction of strengthening precipitates (gamma’ and gamma aEuro(3)) in terms of their number density, which therefore induces the observed softness. Delayed re-precipitation kinetics and the extent of the precipitation of gamma’ and gamma aEuro(3) in the DMHAZ which is related to the diffusion of segregated solute elements from the interdendritic regions are attributed to this phenomenon. The microstructural analyses discussed in this work are vital to adequate understanding of properties of ATI 718Plus produced by the additive manufacturing process technique.

  • 27.
    Asala, Gbenga
    et al.
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, R3T 5V6, Canada.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Ojo, Olanrewaj A.
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, R3T 5V6, Canada.
    Analysis and constitutive modelling of high strain rate deformation behaviour of wire-arc additive-manufactured ATI 718Plus superalloy2019Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 103, nr 1-4, s. 1419-1431Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A fundamental prerequisite for obtaining realistic finite element simulation of machining processes, which has become a key machinability assessment for metals and alloys, is the establishment of a reliable material model. To obtain the constitutive model for wire-arc additive-manufactured ATI 718Plus, Hopkinson pressure bar is used to characterise the flow stress of the alloy over a wide range of temperatures and strain rates. Experiment results show that the deformation behaviours of as-deposited ATI 718Plus superalloy are influenced by the applied strain rate, test temperature and strain. Post-deformation microstructures show localised deformation within the deposit, which is attributable to the heterogeneous distribution of the strengthening precipitates in as-deposited ATI 718Plus. Furthermore, cracks are observed to be preferentially initiated at the brittle eutectic solidification constituents within the localised band. Constitutive models, based on the strain-compensated Arrhenius-type model and the modified Johnson-Cook model, are developed for the deposit based on experimental data. Standard statistical parameters, correlation coefficient (R), root-mean-square error (RMSE) and average absolute relative error (AARE) are used to assess the reliability of the models. The results show that the modified Johnson-Cook model has better reliability in predicting the dynamic flow stress of wire-arc-deposited ATI 718Plus superalloy. © 2019, Springer-Verlag London Ltd., part of Springer Nature.

  • 28.
    Asala, Gbenga
    et al.
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, Canada.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Ojo, Olanrewaj A.
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, Canada.
    Hot corrosion behaviour of wire-arc additive manufactured Ni-based superalloy ATI 718Plus®2019Ingår i: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 158, artikel-id 108086Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The hot corrosion behaviour of wire-arc additive manufactured and wrought ATI 718Plus® are studied. ATI 718Plus® produced by the additive manufacturing process, in the as-processed condition, exhibits a significantly lower hot corrosion resistance in comparison to the wrought alloy. Analytical electron microscopy and spectroscopy techniques, with corroboration by thermodynamic calculations, are used to identify the underlying cause of the poor hot corrosion resistance. Based on the understanding accrued from the analyses, post-processing heat treatments are used to improve the hot corrosion resistance, which is valuably pertinent to the application of ATI 718Plus® produced by additive manufacturing in hot corrosive environments. © 2019 Elsevier Ltd

  • 29.
    Asala, Gbenga
    et al.
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, R3T 5V6, Canada.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Ojo, Olanrewaj A.
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, R3T 5V6, Canada.
    Improved dynamic impact behaviour of wire-arc additive manufactured ATI 718Plus®2018Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 738, s. 111-124Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The dynamic response and impact resistance of wire-arc additive manufactured (AMed) and wrought ATI 718Plus in different heat treatment conditions are characterised by using a direct impact Hopkinson pressure bar system. In addition, microstructural analyses of the alloys, before and after impact, are characterised by using advanced microscopy techniques, including scanning electron and transmission electron microscopies. The experimental results show that the impact resistance of the AMed alloy in the as-processed condition is inferior to that of the wrought alloy. The lower impact resistance is attributed to the presence of eutectic solidification constituents in the interdendritic regions and to the inhomogeneous distribution of the strengthening precipitates in the deposit. After the application of the recommended heat treatment for ATI 718Plus, excessive formation of η-phase particles are observed in the microstructure in addition to Laves phase particles. Since the recommended heat treatment for ATI 718Plus is not sufficient to eliminate the deleterious phases and optimise the properties of the alloy, a novel heat treatment procedure is proposed. Dynamic impact study of the AMed alloy after the application of the proposed approach shows that the alloy exhibits a dynamic response and impact resistance comparable to those of the wrought alloy. Furthermore, under high impact momentum, both the wrought and the AMed alloys fail due to the adiabatic shear band. A transmission electron microscopy analysis of the deformed alloys suggests the dissolution of the γ’ precipitates in the shear band as well as in the adjacent regions to the shear band. Increase in the rate of dissolution of the precipitates due to strain-assisted diffusion coupled with an increase in the adiabatic temperature during deformation, are likely causes of the dissolution of the precipitates in the shear band regions. © 2018 Elsevier B.V.

  • 30.
    Asala, Gbenga
    et al.
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, Canada (CAN).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Ojo, Olanrewaju A.
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, Canada (CAN).
    A study of the dynamic impact behaviour of IN 718 and ATI 718Plus® superalloys2019Ingår i: Philosophical Magazine, ISSN 1478-6435, E-ISSN 1478-6443, Vol. 99, nr 4, s. 419-437Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The dynamic impact response of IN 718 and ATI 718Plus®, in both the solution heat treated and age-hardened conditions, were investigated at different deformation temperatures and strain rates using a direct impact Hopkinson pressure bar. Analyses of the results provide a vital but previously not reported information that the ATI 718Plus® offers a higher resistance to damage during high strain rate ballistic impact deformation compared to the most widely used Iron-nickel based superalloy, Inconel 718. ATI 718Plus® showed higher strain hardening and strain rate sensitivity, in both heat treatment conditions, than IN 718. The difference in the deformation behaviour of both alloys, in the annealed condition, is attributable to the compositional modification in ATI 718Plus® which has been reported to lower its stacking fault energy and increases the tendency for deformation twinning. However, in the age-hardened condition, the difference is believed to be related to the disparity in the operative strengthening mechanism, of the precipitates present in both alloys. Furthermore, a higher susceptibility to strain location and the formation of adiabatic shear band, in aged IN 718, is attributable to the stronger temperature-softening characteristics observed in the alloy and to the limited strain hardening tendency under dynamic impact loading. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.

  • 31.
    Aydin, Gökçe
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Valiente Bermejo, Maria Asunción
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Högström, Mats
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Şelte, Aydın
    Uddeholms AB, Hagfors (SWE).
    Oikonomou, Christos
    Uddeholms AB, Hagfors (SWE).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Influence of laser metal deposition process parameters on a precipitation hardening stainless steel2023Ingår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 67, nr 4, s. 1067-1080Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The combination of corrosion resistance and mechanical properties of martensitic precipitation hardening stainless steels (MPHSS) makes them well suited for demanding applications in aerospace, high-pressure gas bottles, or in injection molding of corrosive plastics. Directed energy deposition methods and specifically the laser metal deposition process with powder as feedstock (LMDp) have the potential to be applied in the production of such components. It is well-known that the geometrical features of the deposited beads such as aspect ratio and dilution are crucial for process efficiency and deposition quality. Therefore, this work aims at understanding the influence of the process parameters and the resulting microstructure of a MPHSS modified PH 13-8Mo alloy when using LMDp. Design of experiment (DoE) was used to plan and analyze the influence and interaction of the different LMDp process variables in the geometry of the deposits. It was found that height, width, and depth were statistically significantly influenced by speed, while height was also considerably influenced by the powder feeding rate. In terms of laser power, it was the most significant factor for the width and the depth, but it did not significantly affect the height of the beads. The results showed that the as-deposited microstructure of the modified PH 13-8Mo under the LMDp conditions investigated in this work consists of a martensitic matrix with some amount of primary δ ferrite. The presence of a low amount of retained austenite and aluminum-enriched inclusions was confirmed. This work enhances the fundamental process and material understanding of LMDp of the modified PH 13-8Mo alloy as a first stage in the fabrication of additively manufactured components.

    Ladda ner fulltext (pdf)
    Tidskriftens fulltext
  • 32.
    Aydin, Gökçe
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Şelte, Aydın
    Uddeholms AB, Hagfors (SWE).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Valiente Bermejo, María Asunción
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Towards Laser Metal Deposition of Modified PH 13-8Mo Powder2023Ingår i: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 964, s. 85-90Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Modified PH 13-8Mo alloy exhibits a good combination of corrosion resistance and mechanical properties for demanding applications in aerospace, petrochemical, and tooling industries. Additive manufacturing, specifically the laser metal deposition process with powder as feedstock (LMDp), has the potential to be utilized in these industries. However, very limited knowledge on the LMDp of this alloy currently exists. The aim of this work was, therefore, to deposit a multi-track single layer of modified PH 13-8Mo alloy as a first step towards 3D geometries, and to analyze the resulting microstructure by using Optical Microscopy, Scanning Electron Microscopy, X-Ray Diffraction, Electron Backscatter Diffraction, and micro-hardness. It was found that the multitrack single layer was free from major defects. The microstructure was heterogeneous, and it consisted of a martensitic matrix and small amounts of δ ferrite, austenite, and AlN. The results of this research will be used to tailor the microstructure and properties of future 3D additively manufactured components.

  • 33.
    Babu, Bijish
    et al.
    Mechanics of Sold Materials, Luleå University of Technology, SE-971 87, Luleå, Sweden.
    Charles Murgau, Corinne
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Lindgren, Lars-Erik
    Mechanics of Sold Materials, Luleå University of Technology, SE-971 87, Luleå, Sweden.
    Physically Based Constitutive Model of Ti-6Al-4V for Arbitrary Phase CompositionArtikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    The main challenge in producing aerospace components using Ti-6Al-4V alloy is to employ the optimum process window of deformation rate and temperature in order to achieve desired material properties. Understanding the microstructure property relationship qualitatively is not enough to achieve this goal. Developing advanced material models to be used in manufacturing process simulation is the key to iteratively computeand optimize the process. The focus in this work is on physically based flow stress models coupled with microstructure evolution models. Such a model can be used to simulate processes involving complex and cyclic thermo-mechanical loading

  • 34.
    Baghdadchi, Amir
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Directed Energy Deposition Additive Manufacturing and Welding of Duplex Stainless Steel using Laser Beam2024Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Duplexa rostfria stål (DSS) med en ferritisk-austenitisk mikrostruktur används inom ett brett spektrum av tillämpningar tack vare hög korrosionsbeständighet och goda mekaniska egenskaper. Effektiv och framgångsrik produktion och sammanfogning av DSS kräver noggrann kontroll av processer och en djupgående förståelse av sambanden mellan kemisk sammansättning, termiska cykler, resulterande mikrostrukturer och egenskaper. I detta arbete studerades svetsning och metalldeponering (direct energy deposition) av DSS med hjälp av laseroch resulterande mikrostrukturer samt egenskaper utvärderades.

    I den första delen svetsades ett lägre legerat FDX 27 duplex rostfritt stål, som har en TRIP-effekt (transformation-induced plasticity), med laser och laseruppvärmdes med ren argon eller ren kvävgas som skyddsgas. Svetsgodsets austenitandel var 22% för argonskydd och 39% för kvävgasskydd under svetsningen. Färre nitrider observerades med kvävgasskydd jämfört med argonskydd. Laseruppvärmning påverkade inte signifikant nitrid- eller austenitandelen för argonskydd. Dock resulterade laseruppvärmningen av svetsen med kvävgasskydd i minskad nitridandel samtidigt som austenitandelen ökade till 57%, vilket visar effektiviteten av detta tillvägagångssätt.

    Analys av fasfraktion är viktig för DSS eftersom balansen mellan ferrit och austenit påverkar egenskaperna. För TRIP-stål måste risken för martensitomvandling av austenit under provberedningen också beaktas. Ferrit, austenit och martensit identifierades och kvantifierades med hjälp av ljusoptisk mikroskopi (LOM) och analys med hjälp av diffraktion av bakåtspridda elektroner (EBSD electron backscatter diffraction). Det visade sig att mekanisk polering gav upp till 26% deformationsinducerad martensit, medan ingen martensit observerades efter elektrolytisk polering.

    I den andra delen användes en systematisk metodik i fyra steg för att utveckla procedurer för additiv tillverkning av standardkomponenter i 22% krom DSS med metalldeponering och laser med svetstråd som tillsatsmaterial (DED-LB/w), kombinerad med varmtrådteknologi. I de fyra stegen tillverkades enkelsträngar, enkelväggar, ett block och slutligen en cylinder med en inre diameter på 160 mm, tjocklek på 30 mm och höjd på 140 mm. Genom att implementera denna metodik med en stegvis ökning av den deponerade volymen och geometrisk komplexitet kan additiva tillverkningsprocedurer framgångsrikt användas för utveckling av metallkomponenter med betydande storlekar. Den deponerade mikrostrukturen var ojämn och innehöll upprepade områden med hög ferrithalt och nitrider samt områden med hög andel av austenit. Värmebehandling i 1 timme vid 1100°C homogeniserade mikrostrukturen, löste upp nitriderna och jämnade nästan ut ferrit- och austenitandelarna. Hållfasthet, duktilitet och seghet var goda för cylindern, jämförbara med de av smidda typer av 2205 DSS, både som deponerad och efter värmebehandling. Gropfrätning och korrosionsmotstånd visade att mikrostrukturella skillnader, inklusive förhållande ferrit till austenit, fördelning av legeringselement i ferrit och austenit och närvaro av nitrider, påverkade korrosionsmotståndet för DED-LB/w DSS. Det visades också att, tillsammans med sönderfallet av ferrit till Fe-rika (α) och Cr-rika (αʹ) faser, bidrar kluster av Ni, Mn och Si-atomer till sprödhet vid 475°C hos DSS tillverkade av DED-LB/w.

    Detta arbete har visat att en laser framgångsrikt kan användas som värmekälla vid tillverkning av DSS både för svetsning och additiv tillverkning. Utmaningar som kväveutarmning, låga austenitandelar och bildning av nitrider måste dock hanteras genom noggrann processtyrning och/eller värmebehandling.

    Ladda ner fulltext (pdf)
    fulltext
    Ladda ner fulltext (pdf)
    fulltext
  • 35.
    Baghdadchi, Amir
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Laser Welding and Additive Manufacturing of Duplex Stainless Steels: Properties and Microstructure Characterization2022Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Duplexa rostfria stål (DSS) är viktiga konstruktionsmaterial tack vare derasutmärkta mekaniska egenskaper och goda korrosionsbeständighet. Vid svetsningoch additiv tillverkning krävs noggrann styrning av parametrar och kunskap om processernas inverkan på mikrostrukturen för att uppnå önskade egenskaper.Lasersvetsning, värmebehandling med laser och additiv tillverkning i form av lasermetalldeponering med tråd (LMDw) har därför studerats för DSS.

    Det duplexa stålet FDX 27 lasersvetsades utan tillsatsmaterial och med argon ellerkväve som skyddsgas. Kvävgasskydd gav mer austenit och färre nitrider änargonskydd. En efterföljande laservärmebehandling löste upp nitriderna då kväve användes som skyddsgas och austenithalten ökade till 57%. Austeniten i FDX 27kan vid deformation omvandlas till martensit. Två metoder för identifiering av martensit utvecklades därför: en färgetsmetod för ljusoptisk mikroskopi samt en metod som utnyttjar bakåtspridda elektroner (EBSD) vid elektronmikroskopi.Som mest bildades 26% martensit vid mekanisk provpreparering medan elektropolerade prover endast innehöll austenit och ferrit.

    Procedurer togs fram för additiv tillverkning av komponenter, i 22% krom duplexa rostfria stål, med LMDw kombinerat med varmtrådsteknik. Slutprodukten var en 140 mm hög cylinder med 160 mm inre diameter och tjocklek av 30 mm. Mikrostrukturen var inhomogen med periodiskt omväxlande ferritiska områden med nitrider, och områden med stor andel austenit.Värmebehandling under 1 timme vid 1100oC eliminerade nitriderna och gav en homogen struktur med ca. 50% austenit. De mekaniska egenskaperna var, både före och efter värmebehandling, jämförbara med de typiska för motsvarande stål. Högst hållfasthet uppmättes före värmebehandling med sträckgränsen 765 MPa och brottgränsen 865 MPa, medan den största förlängningen var 35% efter värmebehandling. Slagsegheten var upp till 300 J vid -10oC men varierade med hur provstavens brottanvisning var orienterad relativt byggriktningen.Laser är en lämplig energikälla vid svetsning och additiv tillverkning av duplexa rostfria stål. Utmaningar som kväveförlust, låga austenithalter och nitridbildning kan hanteras med noggrann processkontroll och/eller värmebehandling.

    Ladda ner fulltext (pdf)
    fulltext
  • 36.
    Baghdadchi, Amir
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Cary, Claire
    Department of Materials Science and Engineering, The Ohio State University, Columbus (USA).
    Sridhar, Narasi
    Department of Materials Science and Engineering, The Ohio State University, Columbus (USA).
    Valiente Bermejo, María Asunción
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Fink, Carolin
    Department of Materials Science and Engineering, The Ohio State University, Columbus (USA).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Corrosion resistance and microstructure analysis of additively manufactured 22% chromium duplex stainless steel by laser metal deposition with wire2023Ingår i: Journal of Materials Research and Technology, ISSN 2238-7854, Vol. 26, s. 6741-6756Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Microstructure characteristics and pitting corrosion of a duplex stainless steel (DSS) manufactured by laser metal deposition with wire (LMDw) were studied. The layer-by-layer LMDw process resulted in a mixed microstructure of predominantly ferrite with 2% austenite and chromium-rich nitrides, and reheated regions with ~33% austenite. The high cooling rate of LMDw restricted the distribution of Cr, Mo, and Ni, in ferrite and austenite, while N diffuses from ferrite to austenite. Subsequent heat treatment at 1100 C for 1 h resulted in homogenized microstructure, dissolution of nitrides, and balanced ferrite/austenite ratio. It also led to the redistribution of Cr and Mo to ferrite, and Ni and N to austenite. At room temperature, cyclic potentiodynamic polarization measurements in 1.0 M NaCl solution showed no significant differences in corrosion resistance between the as-deposited and heat-treated samples, despite the differences in terms of ferrite to austenite ratio and elemental distribution. Critical pitting temperature (CPT) was the lowest (60 C) for the predominantly ferritic microstructure with finely dispersed chromium-rich nitrides; while reheated area with ~33% austenite in as-deposited condition achieved higher critical temperature comparable to what was obtained after heat treatment (73 and 68 C, respectively). At temperatures above the CPT, selective dissolution of the ferrite after deposition was observed due to depletion of N, while after heat treatment, austenite preferentially dissolved due to Cr and Mo concentrating in ferrite. In summary, results demonstrate how microstructural differences in terms of ferrite-to-austenite ratio, distribution of corrosion-resistant elements, and presence of nitrides affect corrosion resistance of LMDw DSS.

    Ladda ner fulltext (pdf)
    fulltext
  • 37.
    Baghdadchi, Amir
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Hosseini, Vahid
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Promoting austenite formation in laser welding of duplex stainless steel-impact of shielding gas and laser reheating2021Ingår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 65, s. 499-511Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Avoiding low austenite fractions and nitride formation are major challenges in laser welding of duplex stainless steels (DSS). The present research aims at investigating efficient means of promoting austenite formation during autogenous laser welding of DSS without sacrificing productivity. In this study, effects of shielding gas and laser reheating were investigated in welding of 1.5-mm-thick FDX 27 (UNS S82031) DSS. Four conditions were investigated: Ar-shielded welding, N2-shielded welding, Ar-shielded welding followed by Ar-shielded laser reheating, and N2-shielded welding followed by N2-shielded laser reheating. Optical microscopy, thermodynamic calculations, and Gleeble heat treatment were performed to study the evolution of microstructure and chemical composition. The austenite fraction was 22% for Ar-shielded and 39% for N2-shielded as-welded conditions. Interestingly, laser reheating did not significantly affect the austenite fraction for Ar shielding, while the austenite fraction increased to 57% for N2-shielding. The amount of nitrides was lower in N2-shielded samples compared to in Ar-shielded samples. The same trends were also observed in the heat-affected zone. The nitrogen content of weld metals, evaluated from calculated equilibrium phase diagrams and austenite fractions after Gleeble equilibrating heat treatments at 1100 °C, was 0.16% for N2-shielded and 0.11% for Ar-shielded welds, confirming the importance of nitrogen for promoting the austenite formation during welding and especially reheating. Finally, it is recommended that combining welding with pure nitrogen as shielding gas and a laser reheating pass can significantly improve austenite formation and reduce nitride formation in DSS laser welds. © 2020, The Author(s).

    Ladda ner fulltext (pdf)
    fulltext
  • 38.
    Baghdadchi, Amir
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Hosseini, Vahid
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW). Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Identification and quantification of martensite in ferritic-austenitic stainless steels and welds2021Ingår i: Journal of Materials Research and Technology, ISSN 2238-7854, Vol. 15, s. 3610-3621Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper aims at the phase identification and quantification in transformation induced plasticity duplex stainless steel (TDSS) base and weld metal containing ferrite, austenite, and martensite. Light optical microscopy (LOM) and electron backscatter diffraction (EBSD) analysis were employed to analyze phases. Samples were either mechanically or electrolytically polished to study the effect of the preparation technique. Mechanical polishing produced up to 26% strain-induced martensite. Electrolytic polishing with 150 g citric acid, 300 g distilled water, 600 mL H3PO4, and 450 mL H2SO4 resulted in martensite free surfaces, providing high-quality samples for EBSD analysis. Martensite identification was challenging both with LOM, due to the similar etching response of ferrite and martensite, and with EBSD, due to the similar lattice structures of ferrite and martensite. An optimized Beraha color etching procedure was developed that etched martensite distinctively. A novel step-by-step EBSD methodology was also introduced considering grain size and orientation, which successfully identified and quantified martensite as well as ferrite and austenite in the studied TDSS. Although here applied to a TDSS, the presented EBSD methodology is general and can, in combination with knowledge of the metallurgy of the specific material and with suitable adaption, be applied to a multitude of multiphase materials. It is also general in the sense that it can be used for base material and weld metals as well as additive manufactured materials.

    Ladda ner fulltext (pdf)
    JMR&T
  • 39.
    Baghdadchi, Amir
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Hosseini, Vahid
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Valiente Bermejo, María Asunción
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Axelsson, Björn
    Alfa Laval Tumba AB, Tumba (SWE).
    Harati, Ebrahim
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). ITW Welding AB,Partille (SWE).
    Högström, Mats
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW). Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Wire laser metal deposition additive manufacturing of duplex stainless steel components -Development of a systematic methodology2021Ingår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 14, nr 23, artikel-id 7170Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A systematic four-stage methodology was developed and applied to the Laser Metal Deposition with Wire (LMDw) of a duplex stainless steel (DSS) cylinder > 20 kg. In the four stages, single-bead passes, a single-bead wall, a block, and finally a cylinder were produced. This stepwise approach allowed the development of LMDw process parameters and control systems while the volume of deposited material and the geometrical complexity of components increased. The as-deposited microstructure was inhomogeneous and repetitive, consisting of highly ferritic regions with nitrides and regions with high fractions of austenite. However, there were no cracks or lack of fusion defects; there were only some small pores, and strength and toughness were comparable to those of the corresponding steel grade. A heat treatment for 1 h at 1100 degrees (C) was performed to homogenize the microstructure, remove nitrides, and balance the ferrite and austenite fractions compensating for nitrogen loss occurring during LMDw. The heat treatment increased toughness and ductility and decreased strength, but these still matched steel properties. It was concluded that implementing a systematic methodology with a stepwise increase in the deposited volume and geometrical complexity is a cost-effective way of developing additive manufacturing procedures for the production of significantly sized metallic components.

    Ladda ner fulltext (pdf)
    Materials
  • 40.
    Baghdadchi, Amir
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Hosseini, Vahid
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Valiente Bermejo, María Asunción
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Axelsson, Björn
    Alfa Laval Tumba AB, Tumba (SWE).
    Harati, Ebrahim
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). ITW Welding AB, Partille (SWE).
    Högström, Mats
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Wire laser metal deposition of 22% Cr duplex stainless steel: as-deposited and heat-treated microstructure and mechanical properties2022Ingår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 57, nr 21, s. 9556-9575Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Duplex stainless steel (DSS) blocks with dimensions of 150 × 70x30 mm3 were fabricated by Laser Metal Deposition with Wire (LMDw). Implementation of a programmable logic control system and the hot-wire technology provided a stable and consistent process producing high-quality and virtually defect-free deposits. Microstructure and mechanical properties were studied for as-deposited (AD) material and when heat-treated (HT) for 1 h at 1100 °C. The AD microstructure was inhomogeneous with highly ferritic areas with nitrides and austenitic regions with fine secondary austenite occurring in a periodic manner. Heat treatment produced a homogenized microstructure, free from nitrides and fine secondary austenite, with balanced ferrite and austenite fractions. Although some nitrogen was lost during LMDw, heat treatment or reheating by subsequent passes in AD allowed the formation of about 50% austenite. Mechanical properties fulfilled common requirements on strength and toughness in both as-deposited and heat-treated conditions achieving the highest strength in AD condition and best toughness and ductility in HT condition. Epitaxial ferrite growth, giving elongated grains along the build direction, resulted in somewhat higher toughness in both AD and HT conditions when cracks propagated perpendicular to the build direction. It was concluded that high-quality components can be produced by LMDw and that deposits can be used in either AD or HT conditions. The findings of this research provide valuable input for the fabrication of high-performance DSS AM components

    Ladda ner fulltext (pdf)
    fulltext
  • 41.
    Baghdadchi, Amir
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Movahedi, Mojtaba
    Department of Materials Science and Engineering, Sharif University of Technology, Tehran (IRN).
    Consumable pin-friction stir spot welding of Al-Mg-Si alloy via pre-created hole and refilling: Microstructure evolution, defects, and shear/tensile failure load2023Ingår i: Proceedings of the Institution of mechanical engineers. Part C, journal of mechanical engineering science, ISSN 0954-4062, E-ISSN 2041-2983, Vol. 237, nr 17Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Since Al-Mg-Si alloys are widely used in the transportation industry, it is important to produce a sound and robust weld between the sheets of these alloys. The focus of this work is on the tensile-shear and cross-tension strengths of the consumable pin-friction stir spot welds (CP-FSSWs) without an exit-hole between the Al-6061 aluminum sheets. Before welding, a hole was created at the joint region in the base sheets and then, it was filled using a rotating consumable pin. The tensile-shear, cross-tension, and microhardness tests were employed to evaluate the mechanical properties of the spot welds. The results showed that the pre-created hole was entirely filled during the welding process. While a complete bond was formed between the consumable pin and the lateral surface of the hole, there were three distinct regions at the interface of the pin and the bottom of the hole: complete bond, kissing bond, and defects. Enhancement of the tool rotational speed decreased the area of the complete bond in the weld compared to the other regions. A linear relationship existed between the bonding area and weld failure load in the cross-tension test. The proposed relationship approved the impact of the swirly region at the interface of the base sheets on the weld strength. While in the cross-tension test, the weld failure load decreased from ∼2800 to ∼1950 N, it improved from ∼10,500 to ∼12,000 N in the tensile-shear test with enhancement of the tool rotational speed from 700 to 2000 rpm. The hardness measurements demonstrated that there was no common heat affected zone softening after CP-FSSW.  

  • 42.
    Baghdadchi, Amir
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Patel, Vivek
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Li, Wenya
    State Key Laboratory of Solidification Processing, Shaanxi Key Laboratory of Friction Welding Technologies, Northwestern Polytechnical University, Xi'an, 710072, Shaanxi (CHN).
    Yang, Xiawei
    State Key Laboratory of Solidification Processing, Shaanxi Key Laboratory of Friction Welding Technologies, Northwestern Polytechnical University, Xi'an, 710072, Shaanxi (CHN).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Ductilization and grain refinement of AA7075-T651 alloy via stationary shoulder friction stir processing2023Ingår i: Journal of Materials Research and Technology, ISSN 2238-7854, Vol. 27, s. 5360-5367Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study investigates the microstructural evolution, mechanical properties, and fracture behavior of AA7075-T651 aluminium alloy subjected to stationary shoulder friction stir processing (SSFSP). SSFSP samples were produced at three different rotational speeds in a range of 600–1000 rpm. The results reveal that SSFSP leads to a uniform grain refinement within the Stir Zone (SZ), reducing the grain size to approximately 2–3 μm from the initial 15 μm in the base material (BM) irrespective of the probe rotational speeds. After SSFSP, the elongation increased by over 50 % at the cost of 10 % reduction in the ultimate tensile strength for all samples. It was worth to note that variations in tool rotational speed exhibited minimal influence on the microstructure and mechanical properties, offering wide range of probe rotational speeds. This could be attributed to the use of non-rotating shoulder with prob dominated microstructure in the SZ. Fractographic analysis confirmed the ductile nature of fractures, revealing development of fine dimples due to grain refinement. This work underscores the effectiveness of SSFSP in achieving significant grain refinement followed by drastic increase in ductility, which offers valuable insights for using stationary shoulder at wider range of rotational speed.

    Ladda ner fulltext (pdf)
    fulltext
  • 43.
    Balachandramurthi, Arun Ramanathan
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Moverare, Johan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT). Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Dixit, Nikhil
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Pederson, Robert
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Influence of defects and as-built surface roughness on fatigue properties of additively manufactured Alloy 7182018Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 735, s. 463-474Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electron beam melting (EBM) and Selective Laser Melting (SLM) are powder bed based additive manufacturing (AM) processes. These, relatively new, processes offer advantages such as near net shaping, manufacturing complex geometries with a design space that was previously not accessible with conventional manufacturing processes, part consolidation to reduce number of assemblies, shorter time to market etc. The aerospace and gas turbine industries have shown interest in the EBM and the SLM processes to enable topology-optimized designs, parts with lattice structures and part consolidation. However, to realize such advantages, factors affecting the mechanical properties must be well understood – especially the fatigue properties. In the context of fatigue performance, apart from the effect of different phases in the material, the effect of defects in terms of both the amount and distribution and the effect of “rough” as-built surface must be studied in detail. Fatigue properties of Alloy 718, a Ni-Fe based superalloy widely used in the aerospace engines is investigated in this study. Four point bending fatigue tests have been performed at 20 Hz in room temperature at different stress ranges to compare the performance of the EBM and the SLM material to the wrought material. The experiment aims to assess the differences in fatigue properties between the two powder bed AM processes as well as assess the effect of two post-treatment methods namely – machining and hot isostatic pressing (HIP). Fractography and metallography have been performed to explain the observed properties. Both HIPing and machining improve the fatigue performance; however, a large scatter is observed for machined specimens. Fatigue properties of SLM material approach that of wrought material while in EBM material defects severely affect the fatigue life. © 2018 Elsevier B.V.

  • 44.
    Bates, William P.
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap.
    Patel, Vivek
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Rana, Harikrishna
    Department of Engineering, University of Palermo,Palermo (ITA).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    De Backer, Jeroen
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Friction Welding Process Section, TWI Ltd., Cambridge, CB21 (GBR).
    Igestrand, Mattias
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Fratini, Livan
    Department of Engineering, University of Palermo, Palermo (ITA).
    Correction to: Properties Augmentation of Cast Hypereutectic Al–Si Alloy Through Friction Stir Processing (Metals and Materials International, (2022), 10.1007/s12540-022-01207-7)2023Ingår i: Metals and Materials International, ISSN 1598-9623, E-ISSN 2005-4149, Vol. 29, artikel-id 876Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    The graphic abstract was missing from this article and it has been given in this correction. The original article has been corrected. © 2022, The Author(s) under exclusive licence to The Korean Institute of Metals and Materials.

    Ladda ner fulltext (pdf)
    fulltext
  • 45.
    Bates, William P.
    et al.
    Department of Engineering Science, University West, Trollhättan (SWE).
    Patel, Vivek
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Rana, Harikrishna
    Department of Engineering, University of Palermo, Palermo (ITA).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    De Backer, Jeroen
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS). Friction Welding Process Section, TWI Ltd., Cambridge (GBR).
    Igestrand, Mattias
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Fratini, Livan
    Department of Engineering, University of Palermo, Palermo (ITA).
    Properties Augmentation of Cast Hypereutectic Al-Si Alloy Through Friction Stir Processing2022Ingår i: Metals and Materials International, ISSN 1598-9623, E-ISSN 2005-4149Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present endeavour is to augment mechanical attributes via friction stir processing (FSP) in hypereutectic aluminium-silicon castings by the means of microstructural modifications and defects reduction. Wherein, the study proceeds with mainly two approaches namely, alteration in tool revolution (TR) and the number of FSP passes. The prepared specimens were evaluated investigating volume fraction of porosities, microstructural characterizations and microhardness. Therefrom, the specimen with highest number of passes delivered most uniform properties resulting from the reduction in casting porosities and refined silicon particle uniform distribution throughout friction stir processed zone. This endeavour may be considered as a footstep towards more industrial readied material transformation.

    Ladda ner fulltext (pdf)
    Springer
  • 46.
    Bayock, Francois Njock
    et al.
    Department of Mechanical Engineering, ENSET Douala, University of Douala, PO Box: 1872, Douala (CMR).
    Kah, Paul
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Kibong, Marius
    Laboratory of Technologies and Applied Sciences, University Institute of Technology, University of Douala, PO Box 8698 Douala, (CMR).
    Timba, Sadrack
    Department of Mechanical Engineering, ENSET Douala, University of Douala, PO Box: 1872, Douala(CMR).
    Thermal induced residual stress and microstructural constituents of dissimilar S690QT high-strength steels and 316L austenitic stainless steel weld joints2021Ingår i: MATERIALS RESEARCH EXPRESS, E-ISSN 2053-1591, Vol. 8, nr 7, s. 1-16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of thermal cycle on the residual stress, microstructural constituents, and alloying elements composition of dissimilar S690QT and 316L austenite stainless steel was studied. Finite element model (FEM) using ANSYS 19.1 software and an experimental investigation using gas metal arc welding (GMAW) process with fully austenite filler wire were applied to developed thermal cycle and evaluate residual stress in the heat-affected zone of both materials. The experimental data were recorded using a thermal-cycle sensor (TCS) and x-ray diffraction technique. A microstructural investigation was done using Scanning electron microscopy (SEM) and Energy-Dispersive x-ray Spectroscopy (EDS). The thermal cycle showed the maximum temperature (T (max)) in the HAZ of 316L side (850 degrees C) at a distance of 7 mm away from the centreline of the weld compare to S690QT side. The magnitude of tensile residual stresses in the 316L side decreased as welding heat input increased. The maximum residual stresses were observed on the S690QT side (700 MPa). Microstructural investigations revealed the formation of Bainite, and some retained of austenite at the temperature of 800 degrees C in the coarse grain heat-affected zone (CGHAZ) of S690QT. On 316L side, some grain boundary austenite (GBA), intragranular austenite (IGA), and carbides were observed in the CGHAZ. Compared to the initial microstructure of both materials, a slightly increase of Mn, Cr, and Si were observed at the respective values of 1.90%, 1.25%, and 0.40% on the S690QT side compared to the BM. For 316L side, it indicated an increase of Cr (26%), Mo (5.69%), and Ni (17%) in the alloying element composition compared to the BM. Applying 10 kJ cm(-1) of heat input produced an excellent mechanical property and reduced the formation of carbide, inter-granular corrosion in the microstructure of 316L side.

    Ladda ner fulltext (pdf)
    fulltext
  • 47.
    Bayock, Francois Njock
    et al.
    Lappeenranta Lahti Univ Technol, Lab Welding Technol, POB 20, Lappeenranta 53851, Finland (FIN).
    Kah, Paul
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Salminen, Antti
    Univ Turku, Dept Mech Engn, FI-20014 Turku, Finland (FIN).
    Belinga, Mvola
    Lappeenranta Lahti Univ Technol, Lab Welding Technol, POB 20, Lappeenranta 53851, Finland (FIN).
    Yang, Xiaochen
    Lappeenranta Lahti Univ Technol, Lab Welding Technol, POB 20, Lappeenranta 53851, Finland (FIN).
    Feasibility study of welding dissimilar Advanced and Ultra High Strength Steels2020Ingår i: Reviews on Advanced Materials Science, ISSN 1606-5131, E-ISSN 1605-8127, Vol. 59, nr 1, s. 54-66Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study concerns the weldability of dissimilar Ultra high-strength steel (UHSS) and advanced high-strength steel (AHSS), which is used in the modern machine industry. The materials offered superior strength as well as relatively low weight, which reduces microstructure contamination during a live cycle. The choice of the welding process base of the base material (BM) and welding parameters is essential to improve the weld joint quality. S700MC/S960QC was welded using a gas metal arc welding (GMAW) process and overmatched filler wire, which was performed using three heat input (7, 10, and 15 kJ/cm). The weld samples were characterized by a Vickers-hardness test, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The test reveals a decrease of softening areas in the HAZ and the formation of the stable formation of Bainite-Ferrite for S700MC and Bainite-martensite for S960QC when the heat input of 10 kJ/cm is used. It is recommended to use the GMAW process and Laser welding (Laser beam-MIG), with an optimal welding parameter, which will be achieved a high quality of manufacturing products.

  • 48.
    Bayock, Francois Njock
    et al.
    Department of Mechanical Engineering, ENSET Douala, University of Douala, P.O. Box: 1872, Douala (CMR).
    Mejouyo, Paul William Huisken
    Department of Mechanical Engineering, ENSET Douala, University of Douala, P.O. Box: 1872, Douala (CMR).
    Bisong, Mbelle Samuel
    Department of Mechanical Engineering, ENSET Douala, University of Douala, P.O. Box: 1872, Douala (CMR).
    Kah, Paul
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Investigation of Microstructure, and Mechanical Properties of Dissimilar High and Ultra-High Steel Welded Joints: Application for Extreme Climate Conditions2022Ingår i: Metallurgical and Materials Engineering, ISSN 2217-8961, Vol. 28, nr 4, s. 625-639Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The paper focuses on the technical challenges of producing high-quality welds in modern extreme climate conditions structures, as welds are typically the weakest part of welded structures. Welding is particularly difficult with high-strength and ultra-high-strength steels (HSS-UHSS), which are used in structures to reduce weight. The microstructural compositions and mechanical properties of dissimilar high-strength and ultra-high-strength steels were investigated in this study, which was performed with three different heat inputs (0.8, 1.2, and 1.8 kJ/mm). There was a 2.3Cr, 0.4Si, and 2.8Mn increase on the FGHAZ microstructure of the S960QC side, confirming the temperature increase in that zone. Microhardness results show softening (160 HV5) in the E500 side’s fine grain heat-affected zone (FGHAZ). Bending test results show that when the maximum force applied was 4000N, the fracture angle was close to 149°, and that the fracture zone was oriented exclusively in the FGHAZ, which had the higher softening zone. Tensile results show the fracture zone, which was oriented in the E500 side’s FGHAZ. It was suggested that a heat input of 1.2 kJ/mm be applied to the weld dissimilar joint of TMCP E500-S960QC, which will be beneficial for extreme climate conditions.  

    Ladda ner fulltext (pdf)
    fulltext
  • 49.
    Bolmsjö, Gunnar
    et al.
    Linnaeus University, Växjö, Sweden.
    Ferreira Magalhães, Ana Catarina
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS). Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Cederqvist, L.
    SKB AB, Oskarshamn, Sweden.
    De Backer, Jeroen
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Robotic Friction Stir Welding of complex geometry and mixed materials2018Ingår i: 50th International Symposium on Robotics, ISR 2018, VDE Verlag GmbH , 2018, s. 35-41Konferensbidrag (Refereegranskat)
    Abstract [en]

    Friction stir welding (FSW) is a solid state process for joining materials which has demonstrated advantages compares with other methods which include joining of mixed materials, hard to weld alloys and consistent and high quality. This paper presents a study of robotic FSW initiated by Volvo Skövde plant to join an insert workpiece of extruded aluminium with a cylinder block of aluminium casting. A three-stage procedure was decided to determine the feasibility to apply robotic FSW. The stages included study of welding the mixed materials, weld along the complex joint line with holes and channels close to the joint, and finally welding the cylinder block. The results based on preliminary analysis indicate that the final tests were successful and the process is feasible for the challenging case study. However, further studies are recommended in order to identify the operating parameters window, tool design, and control of the process in order to optimize productivity and quality. © VDE VERLAG GMBH

  • 50.
    Cederberg, Emil
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Influence of welding and additive manufacturing thermal cycles on microstructure and properties of super duplex stainless steel base and weld metal studied by a physical simulation technique2018Självständigt arbete på avancerad nivå (magisterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Super duplex stainless steel (SDSS) is known for its excellent combination of high corrosion resistance and strength. However, the main limitations in SDSS applications are the risk of getting an imbalanced ferrite and austenite fraction and the sensitivity to form intermetallic phases at temperatures between approximately 600-1000 °C. During welding of SDSS, the welding parameters must be selected carefully in order to avoid formation of intermetallic phases such as sigma phase due to slow cooling or multiple reheating. In addition, special care is needed to have a balanced ferrite and austenite fraction. In this work, the influence of multiple thermal cycles and cooling rate on the microstructure of SDSS base and weld metal was investigated. A novel heat treatment method, using a stationary TIG arc, was performed to produce the samples. The test discs were composed of base and weld metal. Five samples were produced including 1, 5, and 15 passes of rapid cooling, one sample with medium cooling and one with slow cooling. The cooling time between 1000-700 °C was aimed at being similar for the pair of 5 passes and medium cooling and the other pair of 15 passes and slow cooling. The material was characterized by light optical microscopy and scanning electron microscopy while hardness mapping and sensitization testing were employed to evaluate the properties. It was revealed that sigma phase was more prone to precipitate in the weld compared to the base metal when exposed to high ageing temperature and repeated thermal cycles. Slow cooling was found to promote sigma phase precipitation more than multiple reheating in the weld metal. In the base metal, a minor difference was found between the slowly cooled and multiple reheated samples. Rapid cooling in multiple reheating generated nitrides in the fusion boundary zone. As more reheating passes were applied, the amount of nitrides decreased. Multipass reheating cycles also resulted in increased hardness and nitrogen depletion adjacent to the fusion boundary zone causing the ferrite content to increase. Based on this study, less sigma phase precipitation in the weld metal was achieved when using multiple reheating passes with low heat input instead of a few passes with high heat input, providing equal accumulative heating time between 1000-700 °C. However, the influence of multiple reheating on the hardness was larger compared to slow cooling.

1234567 1 - 50 av 314
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf