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  • 51.
    Holmberg, Jonas
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Swerea Group.
    Palosaari, Mikko
    Outokumpu Stainless Oy, Stresstech OY.
    Hosseini, Seyed
    Islamic Azad University, Swerea Group.
    Larjosuo, Henri
    Stresstech OY.
    Andersson, Pär Yngve
    Chalmers University of Technology, Orebro University Swerea Group.
    Round Robin Study on Residual Stresses Using X-Ray Diffraction for Shot-Peened Tool Steel Specimens2018In: Residual Stresses 2018, Ecrs-10, Millersville, PA, USA: MATERIALS RESEARCH FORUM LLC , 2018, Vol. 6, p. 51-56Conference paper (Refereed)
    Abstract [en]

    Residual stress measurements using x-ray diffraction is a well established method used within the industrial and academic community to verify the performance of different processes for metallic materials. The measurement gives an absolute value of the stress state which can be used to design and optimize the process route to induce beneficial compressive residual stresses and avoid detrimental tensile stresses. Investigating the uncertainty and accuracy of the measurement system, operator and the material is therefore of high relevance both from an industrial and scientific point of view. Round robin testing is an important way to quantify the uncertainties that could affect the quality of the measured results and hence how a process is optimized and tuned. Such an investigation allows the operator to understand and reduce variations. Current round robin test includes results from five different laboratories using comparable equipments located in Sweden, Finland, Germany and United States. This work focuses on five shot-peened tool steel specimens produced with identical process settings. Additionally, an investigation of the repeatability of the system, influence of the operator, variations within the specimen, and the long time stability of the specimens has been measured.

  • 52.
    Hosseini, S.B.
    et al.
    Chalmers University of Technology, Department of Materials and Manufacturing Technology.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Production Engineering. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Johansson, S
    Lektronik, Ing.f:a, 424 49 Angered, Sweden .
    Klement, Uta
    Chalmers University of Technology, Department of Materials and Manufacturing Technology.
    Kaminski, J
    Chalmers University of Technology, Department of Materials and Manufacturing Technology.
    Ryttberg, K.
    AB SKF, 415 50 Gothenburg.
    Cutting temperatures during hard turning: Measurements and effects on white layer formation in AISI 521002014In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 214, no 6, p. 1293-1300Article in journal (Refereed)
    Abstract [en]

    This paper concerns the temperature evolution during white layer formation induced by hard turning of martensitic and bainitic hardened AISI 52100 steel, as well as the effects of cutting temperatures and surface cooling rates on the microstructure and properties of the induced white layers. The cutting temperatures were measured using a high speed two-colour pyrometer, equipped with an optical fibre allowing for temperature measurements at the cutting edge. Depending on the machining conditions, white layers were shown to have formed both above and well below the parent austenitic transformation temperature, Ac1, of about 750 C. Thus at least two different mechanisms, phase transformation above the Ac1 (thermally) and severe plastic deformation below the Ac1 (mechanically), have been active during white layer formation. In the case of the predominantly thermally induced white layers, the cutting temperatures were above 900 C, while for the predominantly mechanically induced white layers the cutting temperatures were approximately 550 C. The surface cooling rates during hard turning were shown to be as high as 104-105 C/s for cutting speeds between 30 and 260 m/min independent of whether the studied microstructure was martensitic or bainitic. Adding the results from the cutting temperature measurements to previous results on the retained austenite contents and residual stresses of the white layers, it can be summarised that thermally induced white layers contain significantly higher amounts of retained austenite compared to the unaffected material and display high tensile residual stresses. On the contrary, in the case of white layers formed mainly due to severe plastic deformation, no retained austenite could be measured and the surface and subsurface residual stresses were compressive. © 2014 Elsevier B.V.

  • 53.
    Hosseini, Vahid A.
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Aashuri, H.
    Materials Science and Engineering Dep., Sharif University of Technology, Tehran, Iran.
    Kokabi, A. H.
    Materials Science and Engineering Dep., Sharif University of Technology, Tehran, Iran.
    Study of the effect of tool geometry on semisolid stir welding of a AZ91 magnesium alloy2015In: Proceedings of the 18th International Conference on Joining Materials, JOM-Institute , 2015, p. 1-10Conference paper (Refereed)
    Abstract [en]

    Semisolid stir welding is a newly developed method suitable for joining of the magnesium alloy AZ91. In this study, the effect of tool geometries on the joint properties such as bending strength and the occurrence of porosity are studied. A 2 mm-thick Mg-25%Zn interlayer was placed between two AZ91 plates and the plate was heated up to 530°C before joining. At this temperature, when both the interlayer and the base metal were in the semisolid state, a stirrer was introduced into the joint. Drill-tip and round shape stirrer tools were employed at three different stirring rates. Welds produced with the two methods showed similar properties in the shear punch test. However, using the round tool geometry resulted in welds with excellent bending strength closely matching that of the base metal especially at the highest stirring rate. The improved properties when using the round tool was a result of the formation of a very fine and uniform microstructure with a low content of porosity.

  • 54.
    Hosseini, Vahid
    et al.
    University West, Department of Engineering Science, Division of Welding Technology. Hogskolan Vast.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Welding Technology.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Welding Technology.
    Effect of multipass TIG welding on the corrosion resistance and microstructure of a super duplex stainless steel2017In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 68, no 4, p. 405-415Article in journal (Refereed)
    Abstract [en]

    This is a study of the effect of repetitive TIG (tungsten inert gas) welding passes, melting and remelting the same material volume on microstructure and corrosion resistance of 2507 (EN 1.4410) super duplex stainless steel. One to four weld passes were autogenously (no filler added) applied on a plate using two different arc energies and with pure argon shielding gas. Sensitization testing showed that multipass remelting resulted in significant loss of corrosion resistance of the weld metal, in base material next to the fusion boundary, and in a zone 1 to 4 mm from the fusion boundary. Metallography revealed the main reasons for sensitization to be a ferrite-rich weld metal and precipitation of nitrides in the weld metal, and adjacent heat affected zone together with sigma phase formation at some distance from the fusion boundary. Corrosion properties cannot be significantly restored by a post weld heat treatment. Using filler metals with higher nickel contents and nitrogen containing shielding gases, are therefore, recommended. Welding with a higher heat input and fewer passes, in some cases, can also decrease the risk of formation of secondary phases and possible corrosion attack.

  • 55.
    Jafari, R.
    et al.
    Department of Material Science and Engineering, Tarbiat Modares University, Tehran, Iran.
    Sadeghimeresht, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Shahrabi Farahani, T.
    Department of Material Science and Engineering, Tarbiat Modares University, Tehran, Iran .
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    KCl-induced corrosion behavior of HVAF-sprayed Ni-based coatings in ambient air2017Conference paper (Other academic)
  • 56.
    Jafari, Reza
    et al.
    Tarbiat Modares University, Department of Material Science and Engineering, Tehran, Iran.
    Sadeghimeresht, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Shahrabi Farahani, Taghi
    Tarbiat Modares University, Department of Material Science and Engineering, Tehran, Iran.
    Huhtakangas, Matti
    M. H. Engineering AB, Karlskoga, Sweden .
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    KCl-Induced High Temperature Corrosion Behavior of HVAF-Sprayed Ni-Based Coatings in Ambient Air2018In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 27, no 3, p. 500-511Article in journal (Refereed)
    Abstract [en]

    KCl-induced high temperature corrosion behavior of four HVAF-sprayed Ni-based coatings (Ni21Cr, Ni5Al, Ni21Cr7Al1Y, and Ni21Cr9Mo) under KCl deposit has been investigated in ambient air at 600°C up to 168h. The coatings were deposited onto 16Mo3 steel - a widely used boiler tube material.Uncoated substrate, 304L and Sanicro25 were used as reference materials in the test environment.SEM/EDS and XRD techniques were utilized to characterize the as-sprayed and exposed samples.The results showed that the small addition of KCl significantly accelerated degradation to the coatings. All coatings provided better corrosion resistance compared to the reference materials. The alumina-forming Ni5Al coating under KCl deposit was capable of forming a more protective oxide scale compared to the chromia-forming coatings as penetration of Cl through diffusion paths was hindered. Both active corrosion and chromate formation mechanisms were found to be responsible for Page 1 of 23ASM the corrosion damages. The corrosion resistance of the coatings based on the microstructure analysis and kinetics had the following ranking (from the best to worst): Ni5Al >Ni21Cr> Ni21Cr7Al1Y>Ni21Cr9Mo.

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  • 57.
    Jiang, Janna
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Fasth, Angelica
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylen, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Choi, W.B.
    Center for Thermal Spray Research, Stony Brook, NY, USA.
    Microindentation and Inverse Analysis to Characterize Elastic-Plastic Properties for Thermal Sprayed Ti2AlC and NiCoCrAlY2009In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 18, no 2, p. 194-200Article in journal (Refereed)
    Abstract [en]

    Elastic-plastic material properties for HVOF sprayed Ti2AlC (sprayed with Maxthal 211 powder) and plasma sprayed NiCoCrAlY coatings were investigated using modeling and experimental Berkovich microindentation. Optical microstructure evaluations were also performed. The theories of Hertz, Oliver and Pharr were combined with finite element analysis for extracting the material properties. Empirically based material models for both thermal sprayed Ti2AlC and NiCoCrAlY coatings are proposed.

  • 58.
    Jiang, Janna
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Numerical modelling of the compression behaviour of single-crystalline MAX-phase materials2010In: Advanced materials research, ISSN 1022-6680, Vol. 89-91, p. 262-267Article in journal (Refereed)
    Abstract [en]

    In this article a numerical model to describe the mechanical behaviour of nanophased singlecrystalline Ti3SiC2 is proposed. The approach is a two dimensional finite element periodic unit cell consisting of an elastic matrix interlayered with shear deformable slip planes which obey the Hill's yield criterion. The periodic unit cell is used to predict compression material behaviour of Ti3SiC2 crystals with arbitrary slip plane orientations. Stress strain relationships are derived for Ti 3SiC2, and the effect of slip plane volume fraction as well as orientation of the slip planes are investigated. The two main deformation mechanisms of the material namely; ordinary slip and so called kinking are considered in the study.

  • 59.
    Jothi, Sathiskumar
    et al.
    Swansea University Bay Campus, College of Engineering, Engineering East Building, Fabian Way, Swansea, United Kingdom.
    Merzlikin, S.V.
    Max-Planck-InstitutfürEisenforschung GmbH, Max-Planck-Strae 1, Düsseldorf, Germany.
    Croft, T.N.
    Swansea University Bay Campus, College of Engineering, Engineering East Building, Fabian Way, Swansea, United Kingdom.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Brown, S.G.R.
    Swansea University Bay Campus, College of Engineering, Engineering East Building, Fabian Way, Swansea, United Kingdom.
    An investigation of micro-mechanisms in hydrogen induced cracking in nickel-based superalloy 7182016In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 664, p. 664-681Article in journal (Refereed)
    Abstract [en]

    Hydrogen embrittlement of the nickel-iron based superalloy 718 has been investigated using slow strain rate tests for pre-charged material and also in-situ hydrogen charging during testing. Fractography analyses have been carried using scanning electron microscopy, electron back-scattering diffraction and orientation image microscopy concentrating on the influence of microstructural features and associated micro-mechanisms leading to hydrogen induced cracking and embrittlement. It was observed that hydrogen induced transgranular cracking initiates at micro-voids in the crystal lattice. Similar behaviour has been observed in multi-scale finite element chemo-mechanical numerical simulations. In contrast, hydrogen induced localized slip intergranular cracking was associated with the formation of micro-voids in intergranular regions. The effects of grain boundary and triple junction character on intergranular hydrogen embrittlement were also investigated. It was observed that low end high angle misorientations (LHAM), 15°<Ξ ≀ 35°, and critical high angle misorientations (CHAM), 35° < 50°, are preferential sites for hydrogen induced cracking. In contrast, few or no hydrogen induced cracks were observed at low angle misorientations (LAM), 0°≀ Ξ le; 15°, high end high angle misorientations (HHAM), 50°<Ξ ≀ 55°, or special GB misorientations (SGB), Ξ > 55°. Finally, the use of grain boundary engineering techniques to increase the resistance of super alloy 718 to hydrogen induced cracking and embrittlement is discussed. © 2016 Elsevier B.V. All rights reserved.

  • 60.
    Kanhed, Satish
    et al.
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Awasthi, Shikha
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Midha, Swati
    Department of Textile Technology Indian Institute of Technology Delhi New Delhi, 110016, India.
    Nair, Jitin
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Nisar, Ambreen
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Patel, Anup Kumar
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Pandey, Aditi
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Sharma, Rajeev
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Goel, Sneha
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Upadhyaya, Anish
    Powder Metallurgy Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Ghosh, Sourabh
    Department of Textile Technology Indian Institute of Technology Delhi New Delhi, 110016, India.
    Balani, Kantesh
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Microporous Hydroxyapatite Ceramic Composites as Tissue Engineering Scaffolds: An Experimental and Computational Study2018In: Advanced Engineering Materials, ISSN 1438-1656, E-ISSN 1527-2648, Vol. 20, no 7, article id 1701062Article in journal (Refereed)
    Abstract [en]

    Bone‐tissue engineering mandates the development of multi‐functional bioactive porous hydroxyapatite (HAp) scaffolds. Herein, microwave sintered HAp/ZnO and HAp/Ag composite scaffolds with ≈5–19% porosity are developed using 0–30 vol% graphite as a porogen. The mechanical properties of the porous scaffold are analyzed in detail, revealing that even being more porous, the reinforcement of ZnO (9% porosity, hardness of 2.8 GPa, and toughness of 3.5 MPa.m1/2) has shown to have better hardness and fracture toughness when compared to Ag (5% porosity, hardness of 1.6 GPa, and toughness of 2.6 MPa.m1/2). The flexural strength obtained experimentally are complemented with a finite‐element technique that adopts microstructural features in visualizing the effect of porosity on stress distribution. The antibacterial efficacy and cytocompatibility of these composites are validated by increased metabolic activity and conspicuous cell‐matrix interactions. The anticipation of the results reveal that HAp/ZnO (9% porosity) and HAp/Ag (5% porosity) composites can be used as a potential multi‐functional bone implant scaffolds.

  • 61.
    Karimi Neghlani, Paria
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Deng, Dunyong
    Linköping University, Division of Engineering Materials, Linköping, Sweden.
    Sadeghimeresht, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Olsson, Jonas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Ålgårdh, Joakim
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Swerea KIMAB AB, Kista, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Microstructure Development in Track-by-Track Melting of EBM-Manufactured Alloy 7182018In: 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, p. 643-654Conference paper (Refereed)
    Abstract [en]

    Electron beam melting (EBM) is a powder-bed fusion process within the group of additive manufacturing (AM) technology that is used to fabricate high performance metallic parts. Nickel-Iron base superalloys, such as Alloy 718, are subjected to successive heating and cooling at temperatures in excess of 800 °C during the EBM process. Characterization of the dendritic structure, carbides, Laves and δ-phase were of particular interest in this study. These successive thermal cycles influence the microstructure of the material resulting in a heterogeneous structure, especially in the building direction. Hence, the aim of this study was to gain increased fundamental understanding of the relationship between the processing history and the microstructure formed within a single layer. Different numbers of tracks with equal heights were for this purpose produced, varying from one to ten tracks. All tracks used the same process parameters regardless of number and/or position. Microstructure characteristics (sub-grain structure, grain structure and phases) were analyzed by optical microscopy, scanning electron microscopy equipped with energy disperse spectroscopy and electron backscatter diffraction. The direction of dendrites changed in the overlap zones within the tracks due to re-melting of material in the overlap zone. The primary dendrite arm spacings slightly increased along multi-tracks owing to a slight decrease in cooling rate by addition of the next tracks. Epitaxial growth of grains were observed in all samples due to partial re-melting of grains in previous layers and surface nucleation was also found to occur in all tracks.

  • 62.
    Karimi Neghlani, Paria
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Sadeghimeresht, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Åkerfeldt, Pia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Luleå, 971 87, Sweden.
    Ålgårdh, Joakim
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Powder Materials & Additive Manufacturing, Swerea KIMAB AB, Kista, 164 40, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Influence of successive thermal cycling on microstructure evolution of EBM-manufactured alloy 718 in track-by-track and layer-by-layer design2018In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 160, p. 427-441Article in journal (Refereed)
    Abstract [en]

    Successive thermal cycling (STC) during multi-track and multi-layer manufacturing of Alloy 718 using electron beam melting (EBM) process leads to a microstructure with a high degree of complexity. In the present study, a detailed microstructural study of EBM-manufactured Alloy 718 was conducted by producing samples in shapes from one single track and single wall to 3D samples with maximum 10 longitudinal tracks and 50 vertical layers. The relationship between STC, solidification microstructure, interdendritic segregation, phase precipitation (MC, δ-phase), and hardness was investigated. Cooling rates (liquid-to-solid and solid-to-solid state) was estimated by measuring primary dendrite arm spacing (PDAS) and showed an increased cooling rate at the bottom compared to the top of the multi-layer samples. Thus, microstructure gradient was identified along the build direction. Moreover, extensive formation of solidification micro-constituents including MC-type carbides, induced by micro-segregation, was observed in all the samples. The electron backscatter diffraction (EBSD) technique showed a high textured structure in 〈001〉 direction with a few grains misoriented at the surface of all samples. Finer microstructure and possibility of more γ″ phase precipitation at the bottom of the samples resulted in slightly higher (~11%) hardness values compared to top of the samples. © 2018 Elsevier Ltd

  • 63.
    Karlsson, Leif
    et al.
    University West, Department of Engineering Science, Divison of Natural Sciences, Surveying and Mechanical Engineering.
    Börjesson, J.
    ESAB AB, PO Box 8004, Göteborg.
    Orientation relationships of intragranular austenite in duplex stainless steel weld metals2014In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 19, no 4, p. 318-323Article in journal (Refereed)
    Abstract [en]

    Formation and characteristics of fine intragranular austenite were studied for low energy input duplex stainless steel welds. Microstructures were largely ferritic with some allotriomorphic grain boundary austenite, Widmanstätten type austenite, fine intragranular austenite and nitrides. Electron backscattered diffraction analysis revealed that grain boundary austenite had a random orientation relationship (OR) with one of the adjacent ferrite grains and was close to Kurdjumov-Sachs (KS) with the other, whereas Widmanstätten austenite always showed an OR near KS. The finest intragranular austenite was mainly randomly oriented, whereas coarser austenite more often was close to KS. It is argued that the OR of intragranular austenite with the ferritic matrix is governed by a combination of composition, determining driving force for nucleation at temperature, cooling rate and the availability of nitrides acting as nucleation sites. A random OR is most likely for higher cooling rates and compositions promoting nucleation at lower temperatures. © 2014 Institute of Materials, Minerals and Mining.

  • 64.
    Kisielewicz, Agnieszka
    et al.
    University West, Department of Engineering Science, Division of Production Systems.
    Sadeghi, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Production Systems.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Production Systems.
    Palumbo, Gianfranco
    CNR-IFN Institute for Photonics and Nanotechnologies, Physics Department, Bari, Italy.
    Ancona, Antonio
    University West, Department of Engineering Science, Division of Production Systems. CNR-IFN Institute for Photonics and Nanotechnologies, Physics Department, Bari, Italy.
    In-process spectroscopic detection of chromium loss during Directed Energy Deposition of alloy 7182020In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 186, article id 108317Article in journal (Refereed)
    Abstract [en]

    In this work, a fast optical spectrometer was used to monitor the Directed Energy Deposition (DED) process, during the deposition of Alloy 718 samples with different laser power, thus different energy inputs into the material. Spectroscopic measurements revealed the presence of excited Cr I atoms in the plasma plume. The presence was more apparent for the samples characterized by higher energy input. The Cr depletion from these samples was confirmed by lower Cr content detected by Energy-Dispersive X-ray Spectroscopy (EDS) analysis. The samples were also characterized by higher oxidation and high-temperature corrosion rates in comparison to the samples produced with low energy input. These results prove the applicability of an optical emission spectroscopic system for monitoring DED to identify process conditions leading to compositional changes and variation in the quality of the built material.

  • 65.
    Kisielewicz, Agnieszka
    et al.
    University West, Department of Engineering Science, Division of Production Systems.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Production Systems.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Production Systems.
    Ancona, Antonio
    University West, Department of Engineering Science, Division of Production Systems.
    Spectroscopic monitoring of laser blown powder directed energy deposition of Alloy 7182018In: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 25, p. 418-425Article in journal (Refereed)
    Abstract [en]

    Experimental explorations of a spectrometer system used for in-process monitoring of the laser blown powder directed energy deposition of Alloy 718 is presented. Additive manufacturing of metals using this laser process experiences repeated heating and cooling cycles which will influence the final microstructure and chemical composition at every given point in the built. The spectrometer system disclosed, under certain process conditions, spectral lines that indicate vaporisation of chromium. Post process scanning electron microscope energy dispersive spectroscopy analysis of the deposited beads confirmed a reduction of chromium. Since the chromium concentration in Alloy 718 is correlated to corrosion resistance, this result encourages to further investigations including corrosion tests.

  • 66.
    Kumar, Rajiv
    et al.
    IITB-Monash Research Academy, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
    Joardar, Joydip
    International Advanced Research Centre for Powder Metallurgy and New Materials, Hyderabad, India.
    Raman, R.K. Singh
    Department of Mechanical and Aerospace Engineering, Monash University, VIC 3800 Australia.
    Raja, V.S.
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
    Joshi, Shrikant
    University West, Department of Engineering Science, Research Enviroment Production Technology West. International Advanced Research Centre for Powder Metallurgy and New Materials, Hyderabad, India.
    Parida, S.
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
    Effect of chromium and aluminum addition on anisotropic and microstructural characteristics of ball milled nanocrystalline iron2016In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 671, p. 164-169Article in journal (Refereed)
    Abstract [en]

    Prior studies on synthesis of nanocrystalline elements have discussed the effect of ball milling on lattice parameter, crystallite size, and micro-strain. For elemental milled powders, the anisotropic peak broadening does not change with increasing milling time. However, the effect of alloying addition on the anisotropic behavior of ball milled nanocrystalline powders remains an unexplored area. Here we report the effect of chromium and aluminum addition on the anisotropic behavior of iron in nanocrystalline Fe–20Cr–5Al (wt%) alloy powders synthesized by ball milling. The experimental results show that the anisotropic behavior of iron changes towards isotropic with milling. This change was also correlated to the theoretically calculated anisotropic factor from the change in elastic constant of iron due to milling. Addition of alloying elements exhibited a monotonic rise in the lattice parameter with crystallite size, which was attributed to the excess grain boundary interfacial energy and excess free volume at grain boundaries. Transmission electron microscopy image confirmed the crystallite size and nature of dislocation obtained using modified Williamson-Hall method.

  • 67. Lindgren, L-E.
    et al.
    Lundbäck, A.
    Fisk, M.
    Pedersen, R.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Industrial application of computational welding mechanics2015Conference paper (Refereed)
  • 68.
    Lorentzon, John
    et al.
    University West, School of Business, Economics and IT, Division of Business Administration. University West, Department of Engineering Science, Division of Production Engineering.
    Järvstråt, Niklas
    University West, Department of Engineering Science, Division of Production Engineering.
    Josefson, B. L.
    Chalmers University of Technology, Department of Applied Mechanics.
    Modelling chip formation of alloy 7182009In: Journal of Materials Processing Technology, Vol. 209, no 10, p. 4645-4653Article in journal (Refereed)
  • 69.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Dizdar, S.
    Höganäs AB, Höganäs, Sweden.
    Cavitation-erosion resistance of HVAF-sprayed Fe-based metal coatings for marine applications2017Conference paper (Other academic)
  • 70.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Sato, Kazuto
    Fujimi Incoporated.
    Houdkova, Sarka
    University of West Bohemia.
    Smazalova, Eva
    University of West Bohemia.
    Lusvarghi, Luca
    University of Modena and Reggio Emilia.
    Sassatelli, Paolo
    University of Modena and Reggio Emilia.
    Bolelli, Giovanni
    Università degli Studi di Modena e Reggio Emilia, Modena, Italy.
    Tribological Properties of Hard Metal Coatings Sprayed by High Velocity Air Fuel Process2015In: Proceedings of the International Thermal Spray Conference, ASM International, 2015, p. 761-766Conference paper (Refereed)
    Abstract [en]

    Lowering the thermal energy and increasing the kinetic energy of sprayed particles by newly developed HVAF systems can significantly reduce material decarburization, and increases sliding wear and corrosion resistance of hard metal coatings, making HVAF coatings attractive both economically and environmentally over its HVOFs predecessors. Two agglomerated and sintered feedstock powder chemistries, respectively WC-Co (88/12) and WC-CoCr (86/10/4), with increasing primary carbides grain size from 0.2 to 4.0 microns, have been deposited by the latest HVAF-M3 process onto carbon steel substrates. Respective dry sliding wear behaviours and friction coefficients were evaluated at room temperature via Ball-on-disk (ASTM G99-90) wear tests against Al2O3 counterparts, and via Pin-on-disk (ASTM G77-05) wear tests against modified martensitic steel counterparts in both dry and lubricated conditions. Sliding wear mechanisms, with formation of wavy surface morphology and brittle cracking, are discussed regarding the distribution and size of primary carbides. Corrosion behaviours were evaluated via standard Neutral Salt Spray (NSS), Acetic Acid Salt Spray (AASS), accelerated corrosion test and electrochemical polarization test at room temperature. Optimization of coating tribological properties are discussed regarding the suitable selection of primary carbide size for different working load applications

  • 71.
    Majid, Farajian
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Järvstråt, Niklas
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Surface geometry measurements and the experimental and numerical investigation of stress concentration in fillet welds2006In: 59th Annual Assembly and the International Conference of the International Institute of Welding: Sep, Quebec, Canada, 2006Conference paper (Other academic)
  • 72.
    Markocsan, Nicolaie
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Nylén, Per
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Turunen, Erja
    Tampere University of Technology.
    Vuoristo, Petri
    Tampere University of Technology.
    Wigren, Jan
    Volvo Aero Corporation, Trollhättan.
    Thermal spraying in Europe’s Nordic region2007In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 16, no 4, p. 463-464Article in journal (Refereed)
  • 73.
    Markocsan, Nicolaie
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Nylén, Per
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Wigren, Jan
    Volvo Aero Corporation, Surface Technology,Trollhättan.
    Li, X.-H
    Siemens Industrial Turbomachinery,Department of GRDM, Finspång.
    Low thermal conductivity coatings for gas turbine applications2007In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 16, no 4, p. 498-505Article in journal (Refereed)
  • 74.
    Mraz, Lubos
    et al.
    Welding Research Institute - Industrial Institute SR, Račianska 71, 83259 Bratislava, Slovakia .
    Karlsson, Leif
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Mikula, Pavol
    Nuclear Physics Institute ASCR v.v.i., 250 68 Řež, Czech Republic .
    Vrana, Miroslav
    Nuclear Physics Institute ASCR v.v.i., 250 68 Řež, Czech Republic .
    Identification of Weld Residual Stresses Using Diffraction Methods and their Effect on Fatigue Strength of High Strength Steels Welds2014In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 768-769, p. 668-674Article in journal (Refereed)
    Abstract [en]

    It is well known that fatigue strength of welded joints does not depend on steel strength. Better fatigue strength of welded joints, e.g. longer life time of fatigue loaded weld structures, can be achieved with a smooth transition between the weld and the base material to minimize stress concentration. It has also been recognized that residual stresses play a critical role in the fatigue behaviour of welds. In the last decade an extensive research has been performed in order to increase the fatigue strength of high strength steel weldments. The martensite and bainite transformation start temperatures of weld metals have been shown to have a large effect on fatigue life time of high strength steel welds. This is of particular importance if the full potential of high strength steels is to be used in fatigue loaded constructions. A detailed investigation of the effect of phase transformation temperature on residual stress distribution in the vicinity high strength steel welds and its effect on fatigue life time has been performed. The transformation temperature of the weld metal was varied by changing the chemical composition of the filler material. Residual stress distributions have been measured by neutron as well as by X-ray diffraction and fatigue tests have been performed on the fillet welds. A strong effect of weld metal phase transformation temperature on residual stress level was observed. Fatigue strength increased approximately three times when an optimised low transformation temperature filler material was used in comparison to the application of conventional filler material

  • 75.
    Mraz, Lubos
    et al.
    Welding Research Institute - Industrial Institute SR, 832 59 Bratislava, Slovakia.
    Karlsson, Leif
    University West, Department of Engineering Science, Divison of Natural Sciences, Surveying and Mechanical Engineering.
    Vrana, Miroslav
    Nuclear Physics Institute ASCR, v.v.i, 25068 Rez, Czech Republic .
    Mikula, Pavol
    Nuclear Physics Institute ASCR, v.v.i, 25068 Rez, Czech Republic .
    Residual stress distributions at high strength steel welds prepared by low transformation temperature (LTT) and conventional welding consumables2014In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 777, p. 40-45Article in journal (Refereed)
    Abstract [en]

    Residual stress distributions in fillet welds in 8 mm 900 MPa steel have been mapped perpendicular and parallel to the weld line and also through the thickness in the vicinity of weld toe position. Measurements were carried out on four welds when two of them were performed with conventional and two with the so called LTT (low transformation temperature) filler materials. Both neutron and X-ray diffractions were used for determination of the residual stress distribution. Fatigue properties have also been evaluated for all test welds. Neutron diffraction measurements showed that the stress profiles perpendicular to the weld toe qualitatively did not depend on filler material type although the absolute stress levels differed. Trends were similar for positions 2, 4 and 6 millimetres below the surface for all three stress components; σx (direction perpendicular to the weld), σy (parallel to the weld) and σz (through the thickness). X-ray diffraction showed difference in residual stress level at the weld toe. Lower residual stress levels have been identified for LTT filler material when compared to the conventional consumable compositions. The effect of residual stress is discussed in relation to fatigue properties of all four welds. Remarkable higher fatigue strength has been measured for welds prepared by the LTT filler materials. © (2014) Trans Tech Publications, Switzerland.

  • 76.
    Mráz, Lubos
    et al.
    Welding Reseach Insitute - Industrial Insitute of SR, Racinska 71, 832 59 Bratislava, Slovak Republic.
    Karlsson, Leif
    University West, Department of Engineering Science, Divison of Natural Sciences, Surveying and Mechanical Engineering.
    Vrána, Miroslav
    Nuclear Physics Institute AS CR, v.v.i., Řež 130, Czech Republic ..
    Neutron Diffraction Studies of Residual Stress Distribution in the Vicinity of the Single Pass Fillet Steel Welds2015In: Applied Mechanics and Materials, ISSN 1660-9336, E-ISSN 1662-7482, Vol. 732, p. 13-19Article in journal (Refereed)
    Abstract [en]

    In this contribution the results of residual strain/stress measurements performed on several single pass fillet steel welds, which were carried out at different welding conditions, namely, with different filler materials are presented.

  • 77.
    Mráz, Lubos
    et al.
    Welding Research Institute, Industrial Institute SR, Bratislava, Slovakia .
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Vrána, Miroslav
    Nuclear Physics Institute AS CR, v.v.i., Řež 130, Czech Republic .
    Mikula, Pavol
    Nuclear Physics Institute AS CR, v.v.i., Řež 130, Czech Republic .
    Residual stress distribution measurement by neutron diffraction of the single pass fillet steel welds2014In: 52nd International Scientific Conference on Experimental Stress Analysis (EAN 2014): Proceedings of a meeting held 2-5 June 2014, Marianske Lazne, Czech Republic., Czech Society for Mechanics ( CSM ) , 2014Conference paper (Refereed)
    Abstract [en]

    In this contribution the results of residual strain/stress measurements performed on several single pass fillet steel welds which were carried out at different welding conditions, namely, with different filler materials are presented.

  • 78.
    Neikter, Magnus
    et al.
    Luleå University of Technology, Div. Material Science, Luleå, Sweden.
    Forsberg, Fredrik
    Luleå University of Technology, Div. Fluid and Experimental Mechanics, Luleå, Sweden.
    Lycksam, Henrik
    Luleå University of Technology, Div. Fluid and Experimental Mechanics, Luleå, Sweden.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Welding Technology.
    Antti, Marta-Lena
    Luleå University of Technology, Div. Material Science, Luleå, Sweden.
    Microstructure and Defects in Additive Manufactured Titanium: a Comparison Between Microtomography and Optical Microscopy2017Conference paper (Other academic)
    Abstract [en]

    The aim of this work has been to compare two different analysing methods; x-ray microtomography and light optical microscopy, when it comes to defects and microstructure of additively manufactured Ti-6Al-4V. The results show that both techniques have their pros and cons:microtomography is the preferred choice for defect detection by analysing the full 3D sample volume, while light optical microscopy is better for analysing finer details in 2D.

  • 79.
    Nordström, Michael
    et al.
    Saab Automobile AB.
    Järvstråt, Niklas
    University West, Department of Engineering Science, Division of Production Engineering.
    An appearance-based measure of surface defects2009In: International Journal of Material Forming, Vol. 2, no 2, p. 83-91Article in journal (Refereed)
  • 80.
    Ott, Eric
    et al.
    General Electric, Cincinnati, USA.
    Liu, XingboWest Virginia University, Morgantown, USA.Andersson, JoelUniversity West, Department of Engineering Science, Division of Welding Technology.BI, ZhongnanChina Iron and Steel Research Institute, Beijing, China.Bockenstedt, KevinATI Specialty Materials, Monroe, USA.Dempster, IanWyman Gordon Forgings Inc., Houston, USA.Groh, JonGeneral Electric, Cincinnati, USA.Heck, KarlCarpenter Technology, Philadelphia, USA.Jablonski, PaulUnited States Department of Energy, Albany, USA.Kaplan, MaxPratt & Whitney, East Hartford, USA.Nagahama, DaisukeHonda Motor Co. Ltd.SaitamaJapan.Sudbrack, ChantalQuesTek Innovations, Evanston, USA.
    Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives: Energy, Aerospace, and Industrial Applications2018Conference proceedings (editor) (Other academic)
    Abstract [en]

    This technical meeting will focus on Alloy 718 and Superalloys in this class relative to alloy and process development, production, product applications, trends and the development of advanced modeling tools. The symposium provides an opportunity for authors to present technical advancements relative to a broad spectrum of areas while assessing their impact on related fields associated with this critical alloy group. There are continuing innovations relative to these alloys as well as novel processing techniques which continue to extend applications in very challenging environments ranging from corrosion resistance in the deep sea to high-stressed space applications.

  • 81.
    Panwisawas, C.
    et al.
    University of Birmingham, School of Metallurgy and Materials, UK.
    Sovani, Y.
    University of Birmingham, School of Metallurgy and Materials, UK.
    Anderson, M.J.
    University of Birmingham, School of Metallurgy and Materials, UK.
    Turner, R.
    University of Birmingham, School of Metallurgy and Materials, UK.
    Palumbo, N. M.
    Rolls-Royce plc, Derby, UK.
    Saunders, B. C.
    Rolls-Royce plc, Derby, UK.
    Choquet, Isabelle
    University West, Department of Engineering Science, Division of Welding Technology.
    Brooks, J.W.
    University of Birmingham, School of Metallurgy and Materials, UK.
    Basoalto, H.C.
    University of Birmingham, School of Metallurgy and Materials, UK.
    A Multi-scale Multi-physics Approach to Modelling of Additive Manufacturing in Nickel-based Superalloys2016In: Superalloys 2016: Proceedings of the 13th International Symposium on Superalloys / [ed] M. Hardy, E. Huron, U. Glatzel, B. Griffin, B. Lewis, C. Rae, V. Seetharaman och S. Tin, Minerals, Metals & Materials Society, 2016, p. 1021-1030Conference paper (Refereed)
    Abstract [en]

    A multi-scale, multi-physics modelling framework of selective laser melting (SLM) in the nickel-based superalloy IN718 is presented. Representative powder-bed particle distribution is simulated using the measured size distribution from experiment. Thermal fluid dynamics calculations are then used to predict melting behaviour, sub-surface morphology, and porosity development during a single pass scanning of the SLM process. The results suggest that the pores and uneven surface structure are exacerbated by increasing powder layer thicknesses. Predicted porosity volume fraction is up to 12% of the single track when 5 statistical powder distributions are simulated for each powder layer thickness. Processing-induced microstructure is predicted by linking cellular automatons – finite element calculations indicate further that the cooling rate is about 4400 o C/s and grain growth strongly follows the thermal gradient giving rise to a columnar grain morphology if homogeneous nucleation is assumed. Random texture is likely for as-fabricated SLM single pass with approximately 8 Pm and 6 Pm grain size for 20 Pm and 100 Pm powder layer thickness fabrication. Use has been made of the cooling history to predict more detailed microstructure using a γ" precipitation model. With the short time scale of solidification and rapid cooling, it becomes less likely that γ" precipitation will be observed in the condition investigated unless a prolonged hold at temperature is carried out. Future work on extension of the proposed multiscale modelling approach on microstructure predictions in SLM to mechanical properties will be discussed.

  • 82.
    Ramjaun, T.
    et al.
    University of Cambridge.
    Stone, H. J.
    Unversity of Cambridge.
    Karlsson, Leif
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Gharghouri, M.A.
    Canadian Neutron Beam Centre, Chalk River Laboratories, Chalk River, Ont. K0J 1J0, Canada.
    Dalaei, K
    ESAB AB, Lindholmsalln 9, 417 55 Göteborg.
    Moat, R..J
    Materials Engineering, The Open University, Milton Keynes MK7 6AA, UK.
    Bhadeshia, H.K.D.H.
    University of Cambridge.
    Surface residual stresses in multipass welds produced using low transformation temperature filler alloys2014In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 19, no 7, p. 623-630Article in journal (Refereed)
    Abstract [en]

    Tensile residual stresses at the surface of welded components are known to compromise fatigue resistance through the accelerated initiation of microcracks, especially at the weld toe. Inducement of compression in these regions is a common technique employed to enhance fatigue performance. Transformation plasticity has been established as a viable method to generate such compressive residual stresses in steel welds and exploits the phase transformation in welding filler alloys that transform at low temperature to compensate for accumulated thermal contraction strains. Neutron and X-ray diffraction have been used to determine the stress profiles that exist across the surface of plates welded with low transformation temperature welding alloys, with a particular focus on the stress at the weld toe. For the first time, near surface neutron diffraction data have shown the extent of local stress variation at the critical, fusion boundary location. Compression was evident for the three measurement orientations at the fusion boundaries. Compressive longitudinal residual stresses and tensile transverse stresses were measured in the weld metal.

  • 83.
    Ramjaun, T.
    et al.
    University of Cambridge.
    Stone, H. J.
    Unversity of Cambridge.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Kelleher, J.
    ISIS Facility, Rutherford Appleton Laboratory.
    Moat, R. J.
    The Open University.
    Kornmeier, J. R.
    Forschungs-Neutronenquelle Heinz Maier-Leibnitz.
    Kemellia, Dalaei
    ESAB AB, Lindholmsalln 9, 417 55 Göteborg.
    Bhadeshia, H.K.D.H.
    University of Cambridge.
    Effect of interpass temperature on residual stresses in multipass welds produced using low transformation temperature filler alloy2014In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 19, no 1, p. 44-51Article in journal (Refereed)
    Abstract [en]

    Weld filler alloys that exploit transformation plasticity through low austenite to martensite transformation temperatures offer an effective method of reducing residual stresses in strong steel welds. However, in multipass welds, the heat input from later weld passes may be insufficient to retransform prior welding passes, leading to the accumulation of thermally induced strains and elevated residual stresses. In this work, the residual stress distributions produced around arc welds fabricated with a martensitic weld filler alloy that transforms at a low temperature have been studied as a function of the number of passes deposited and the interpass temperature. It is found that when the interpass temperature is above the transformation temperature of the weld metal, the entire multipass weld transforms as a single entity, thus permitting the optimum exploitation of the transformation plasticity. In contrast, the deposition of new metal with a relatively low interpass temperature leads to increased residual stresses in the underlying layers, reducing or eliminating the beneficial stress states previously created.

  • 84.
    Ramjaun, T.
    et al.
    University of Cambridge.
    Stone, H. J.
    Unversity of Cambridge.
    Karlsson, Leif
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Kelleher, J.
    ISIS Facility, Rutherford Appleton Laboratory.
    Ooi, S.W.
    University of Cambridge.
    Dalaei, K
    ESAB AB, Lindholmsalln 9, 417 55 Göteborg.
    Kornmeier, J. R.
    Forschungs-Neutronenquelle Heinz Maier-Leibnitz.
    Bhadeshia, H.K.D.H.
    University of Cambridge.
    Effects of dilution and baseplate strength on stress distributions in multipass welds deposited using low transformation temperature filler alloys2014In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 19, no 6, p. 461-467Article in journal (Refereed)
    Abstract [en]

    Transformation plasticity can be utilised to control residual stresses in steel welds. This requires special filler alloys that transform at a sufficiently low temperature to compensate for accumulated thermal contraction strains. However, the welding parameters needed to optimise the effect in multipass joints have yet to be established. This topic has been investigated by characterising the residual stress distribution in multipass welds fabricated with different welding alloys and baseplates using neutron diffraction to assess the effects of dilution and baseplate strength. While the use of richly alloyed weld metal does enhance fatigue performance in single pass joints, the extent of stress relief that can be derived from transformation plasticity is reduced due to incomplete martensitic transformation when further layers are deposited. For all cases studied, compressive stresses were measured in the weld metal with balancing tensile stress in the heat affected zone of the plate. The magnitude of the tension was observed to be a function of the strength of the baseplate. Recommendations are also presented for the combination of welding and material parameters that lead to the optimum exploitation of transformation plasticity as a method for boosting the fatigue performance of multipass welded joints.

  • 85.
    Sadeghi, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Karimi Neghlani, Paria
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Momeni, Soroush
    Friedrich-Alexander University Erlangen-Nurnberg, Department of Materials Science and Engineering, Erlangen, 91058, Germany.
    Seifi, Mohsen
    Case Western Reserves University, Department of Materials Science & Engineering, Cleveland, 44106,USA; ASTM International, Washington, DC 20036, United States .
    Eklund, Anders
    Quintus Technologies AB, Västerås, 721 66, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Influence of thermal post treatments on microstructure and oxidation behavior of EB-PBF manufactured Alloy 7182019In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 150, p. 236-251Article in journal (Refereed)
    Abstract [en]

    The effect of thermal post treatments consisting of heat treatment (HT), hot isostatic pressing (HIP), and combined HIP-HT on microstructure and oxidation behavior of Alloy 718 manufactured by electron beam powder bed fusion (EB-PBF) technique was investigated. Oxidation of the as-built and post-treated specimens was performed in ambient air at 650, 750, and 850 °C for up to 168 h. Directional columnar-grained microstructure, pores and fine Nb-rich carbides were observed in the as-built specimen. The HT specimen presented the columnar microstructure, plate-like δ phase at grain boundaries, and pores. The dominant grain crystallographic orientation was changed from 〈001〉 in the as-built specimen to 〈101〉 after HT. No grain boundary δ phase was observed in the HIPed specimen, but recrystallization occurred in both the HIP and HIP-HT specimens due to a rapid cooling after HIPing motivating the nucleation of fine grains with limited time to grow. After oxidation exposure at 650 and 750 °C for 168 h, no big difference between weight changes of the as-built and post-treated specimens was noted, whereas at 850 °C, the combined HIP-HT specimen showed the most promising corrosion resistance with the least weight change. At 850 °C, a protective scale of Cr 2 O 3 rich in Cr, Ti, and Ni as well as an internal oxide (branched structure of alumina) developed in all the specimens, while, only a protective Cr 2 O 3 scale was found at 650 and 750 °C. The HIP-HT specimen at 850 °C developed an oxide scale, which was denser and more adherent in comparison to the oxide scales formed on the other three specimens, associated with its limited defect distribution and more homogenized microstructure. Moreover, the δ phase formed close to the surface of the exposed specimens during the oxidation exposure at 850 °C most probably led to nucleation and growth of the oxide scale. © 2019 Elsevier Inc.

  • 86.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Eklund, Johan
    University of Chalmers, Gothenburg, Sweden.
    Phother Simon, Julien
    University of Chalmers, Gothenburg, Sweden.
    Liske, Jesper
    University of Chalmers, Gothenburg, Sweden.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    HVAF spraying for biomass boiler applications:: Oxidation behavior of Ni-based coatings in moisture-laden environment2017Conference paper (Other academic)
  • 87.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Karimi Neghlani, Paria
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Zhang, Pimin
    Linköping University,Department of Management and Engineering, Linköping, Sweden.
    Peng, Ru
    Linköping University,Department of Management and Engineering, Linköping, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology, Örebro, Sweden.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Isothermal Oxidation Behavior of EBM-Additive Manufactured Alloy 7182018In: 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, p. 219-240Conference paper (Refereed)
    Abstract [en]

    Oxidation of Alloy 718 manufactured by electron beam melting (EBM) process has been undertaken in ambient air at 650, 700, and 800 °C for up to 168 h. At 800 °C, a continuous external chromia oxide enriched in (Cr, Ti, Mn, Ni) and an internal oxide that was branched structure of alumina formed, whereas at 650 and 700 °C, a continuous, thin and protective chromia layer was detected. The oxidation kinetics of the exposed EBM Alloy 718 followed the parabolic rate law with an effective activation energy of ~248 ± 22 kJ/mol in good agreement with values in the literature for conventionally processed chromia-forming Ni-based superalloys. The oxide scale formed on the surface perpendicular to the build direction was slightly thicker, and more adherent compared to the scale formed on the surface along the build direction, attributed to the varied grain texture in the two directions of the EBM-manufactured specimens. The increased oxygen diffusion and high Cr depletion found on the surface along the build direction were attributed to the fine grains and formation of vacancies/voids along this grain orientation.

  • 88.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Reddy, Liam
    The University of Nottingham, Faculty of Engineering, Nottingham, UK.
    Hussein, Tanvir
    The University of Nottingham, Faculty of Engineering, Nottingham, UK.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Chlorine-induced high temperature corrosion of HVAF-sprayed Ni-based alumina and chromia forming coatings2018In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 132, no March, p. 170-184Article in journal (Refereed)
    Abstract [en]

    Chlorine-induced corrosion of HVAF-sprayed Ni21Cr and Ni5Al coatings was investigated in 5 vol.% O2 + 500vppm HCl + N2 with and without KCl at 600 °C up to 168 h. Both coatings were protective in the absence of KCl. With KCl, Ni21Cr degraded through a two-stage mechanism: 1) formation of K2CrO4 followed by diffusion of Cl− through the oxide grain boundaries to yield chlorine and a non-protective oxide, and 2) inward diffusion of chlorine though defects in the non-protective oxide, leading to breakaway oxidation. Cl−/Cl2 could not diffuse through the protective alumina scale formed on Ni5Al, hence the corrosion resistance increased.

  • 89.
    Segerstark, Andreas
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Review of Laser Deposited Superalloys Using Powder as an Additive2014In: 8th International Symposium on Superalloy 718 and Derivatives: Conference Proceedings / [ed] Ott, E., Banik, A., Andersson, J., Dempster, I., Gabb, T., Groh, J., Heck, K., Helmink, R., Liu, X. & Wusatowska-Sarnek, A, John Wiley & Sons, 2014, p. 393-408Conference paper (Refereed)
  • 90.
    Singh, Sukhdeep
    et al.
    Chalmers University of Technology,Department of Industrial and Materials Science, Gothenburg, Sweden.
    Fransson, William
    University West, Department of Engineering Science.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Brederholm, Anssi
    Aalto University School of Engineering, Helsinki, Finland.
    Hänninen, Hannu
    Aalto University School of Engineering, Helsinki, Finland.
    Varestraint Weldability Testing of ATI 718Plus®: Influence of Eta Phase2018In: Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives: Energy, Aerospace, and Industrial Applications / [ed] Eric Ott, Xingbo Liu, Joel Andersson, Zhongnan Bi, Kevin Bockenstedt, Ian Dempster, Jon Groh, Karl Heck, Paul Jablonski, Max Kaplan, Daisuke Nagahama, Chantal Sudbrack, Springer, 2018, p. 929-937Conference paper (Refereed)
    Abstract [en]

    This study investigates the effect of eta phase on hot cracking susceptibility of ATI 718Plus®. Two heat treatment conditions of 950 °C/1 h and 950 °C/15 h having different amounts of eta phase were tested by longitudinal Varestraint testing method. The heat treatment at 950 °C/15 h exhibited the highest amount of cracking. This was related to the higher amount of eta phase precipitation during the long dwell heat treatment which aided to extensive liquation during welding.

  • 91.
    Singh, Sukhdeep
    et al.
    Department of Industrial and Materials Science, Chalmers University of Technology, Gothenburg, Sweden.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Welding Technology.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Investigation on effect of welding parameters on solidification cracking of austenitic stainless steel 3142018In: Procedia Manufacturing, E-ISSN 2351-9789, p. 351-357Article in journal (Other academic)
    Abstract [en]

    This study investigates the solidification cracking susceptibility of the austenitic stainless steel 314. Longitudinal Varestraint testing was used with three different set of welding test parameters. Weld speed, current and voltage values were selected so that the same heat input resulted in all the test conditions. From the crack measurements it was seen that the test condition with the lowest current and welding speed value also produced the least amount of cracking with very good repeatability.

  • 92. Sjöberg, Göran
    et al.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Sjunnesson, Anders
    New Materials in the Design and Manufacturing of Hot Structures for Aircraft Engines: Allvac 718Plus2009In: XIX International Symposium on Air Breathing Engines 2009: ISABE 2009, Montreal, Canada, 7-11 September, 2009., Reston, VA: American Institute of Aeronautics and Astronautics, 2009, Vol. 3, p. 1406-1415Conference paper (Refereed)
  • 93.
    Steffenburg-Nordenström, Joachim
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. GKN Aerospace Sweden.
    Larsson, Mats
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Simulation of the influence of forming on residual stresses and deformations after welding and heat treatment in Alloy 7182014In: / [ed] E. Oñate, J. Oliver and A. Huerta, International Center for Numerical Methods in Engineering (CIMNE), 2014, p. 1657-1666Conference paper (Other academic)
    Abstract [en]

    Manufacturing of components in aero engines requires attention to residual stress and final shape of the product in order to meet high quality product standards. This sets very high demands on involved manufacturing steps. The manufacturing of a V-shaped leading edge of a vane is simulated. It is made of Alloy718, which is a nickel based heat resistant material commonly used in aerospace components. The manufacturing process chain consists of forming, welding and heat treatment. The results show that the remaining residual stresses after a manufacturing process chain are affected when the residual history from the formingprocess is considered. The residual stress decrease after heat treatment is about 55-65%. Moreover, the von Mises stress profile through thickness at the centre of the radius at the weld joint is about 25% higher when full forming history is considered.

  • 94.
    Stenbacka, Nils
    University West, Department of Engineering Science.
    Kan man svetsa i äldre stålkonstruktioner2011In: Stålbyggnad, ISSN 1404-9414, no 3, p. 52-54Article in journal (Other academic)
  • 95.
    Tofeldt, Oskar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Pierce, S.G.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Smillie, G.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Kerr, W.
    Advanced Forming Research Centre, Inchinnan, Renfrewshire, UK.
    Flockhart, G.M.H.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Macleod, C.N.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Blue, R.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Gachagan, A.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Stratoudaki, T.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Olsson, Jonas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    McMahon, D.
    Advanced Forming Research Centre, Inchinnan, Renfrewshire, UK.
    Investigation of fundamental ultrasonic propagation characteristics in NDT of Electron Beam Melted additive manufactured samples: Inconel 7182018Conference paper (Other academic)
    Abstract [en]

    New approaches for efficient NDT inspection of modern additively manufactured metallic components are required urgently to qualify and validate the next generation of metallic parts across a range of industries. Ultrasonic testing is a fundamental component of NDT for such additive manufacturing processes. This work studies the ultrasonic propagation characteristics of EBM manufactured sample coupons in Inconel 718material. Fundamental longitudinal and shear wave velocity measurements are experimentally measured in 3 orthogonal build directions of the sample coupons. Results show a dependency of the ultrasonic velocities and the build direction. The measured velocities are further verified in a phased array measurement showing successful results that highlights the potential of continued studies with synthetic apertures techniques.

  • 96.
    Valiente Bermejo, María Asunción
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    DebRoy, Tarasankar
    University Park, Department of Materials Science and Engineering, The Pennsylvania State University, State College PA 16801, USA.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Karlsson, Leif
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Production Engineering.
    Towards a Map of Solidification Cracking Risk in Laser Welding of Austenitic Stainless Steels2015In: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 78, p. 230-239Article in journal (Refereed)
    Abstract [en]

    In this work, two series of specimens with Hammar and Svensson's Cr- and Ni-equivalents (Creq+Nieq) = 35 and 45 wt% were used to cover a wide range of austenitic grades. These were laser welded with different energy inputs achieving cooling rates in the range of 103 °C/s to 104 °C/s. As high cooling rates and rapid solidification conditions could favour fully austenitic solidification and therefore raise susceptibility to solidification cracking, the solidification modes of the laser welded specimens were compared to the ones experienced by the same alloys under arc welding conditions. It was found that high cooling rates experienced in laser welding promoted fully austenitic solidification for a wider range of compositions, for example specimens with (Creq+Nieq) = 35% under arc welding cooling conditions at 10 °C/s showed fully austenitic solidification up to Creq/Nieq = 1.30, whilst the same specimens laser cooled at 103 °C/s showed fully austenitic solidification up to Creq/Nieq = 1.50 and those cooled at 104 °C/s showed it up to Creq/Nieq = 1.68. Therefore, high cooling rates extended the solidification cracking risk to a wider range of Creq/Nieq values. This work also compares the cooling rates experimentally determined by thermocouples to the computed cooling rates calculated by a highly-advanced computational model. The distance between the thermocouple's wires and the thermal resistance of thermocouples together with the small size of the weld pools proved to be practical limitations in the experimental determination of cooling rates. However, an excellent agreement was found between computed and experimental solidus isotherms at high energy input settings. For low energy input settings cooling rate was in the order of magnitude of 104 °C/s, whilst for high energy input settings cooling rate was found to be in the order of magnitude of 103 °C/s.

  • 97.
    Valiente Bermejo, María Asunción
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    DebRoy, Tarasankar
    Pennsylvania State University.
    Influence of low energy laser welding on solidification and microstructure of austenitic stainless steel welds2013In: 14th NOLAMP Conference: The 14th Nordic Laser Materials Processing Conference, August 26th – 28th 2013, Gothenburg, Sweden / [ed] Alexander Kaplan, Hans Engström, Luleå: Luleå University of Technology, 2013, p. 3-14Conference paper (Refereed)
    Abstract [en]

    Primary austenitic solidification is related to increased hot cracking susceptibility in welding of austenitic stainless steels. It is also recognised that high cooling rates and rapid solidification conditions, like those achieved in laser beam welding (LBW), increase the stability of austenite versus ferrite as the primary solidification phase. Knowledge about the solidification mode under LBW conditions is therefore of utmost importance. A series of austenitic stainless steel alloys were prepared using an electric arc furnace and cooled at a rate of 10 ºC/s. The overall alloying composition was kept constant at [Cr eq+Nieq] = 40 wt% while changing the Cr eq/Nieq ratio from 1.52 to 1.84. These alloys were then laser welded using a continuous wave ytterbium fibre laser at two different energy input levels. Cooling rates were experimentally determined to be in the range of 10 3 ºC/s to 104 ºC/s and the values were confirmed by computational modelling. The compositional border between primary austenitic and primary ferritic solidification was found to shift to higher Cr eq/Nieq values at higher cooling rates. However, all the alloys showed coexistence of regions of primary austenitic and primary ferritic solidification for both laser settings although ustenite tended to more abundant at higher cooling rates. Austenite content and refinement of microstructure is discussed in terms of effects of cooling rate on solidification behaviour and solid state transformations.

  • 98.
    Valleti, Krishna
    et al.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, India.
    Puneet, C.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, India.
    Rama Krishna, L.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, India.
    Joshi, Shrikant
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Studies on cathodic arc PVD grown TiCrN based erosion resistant thin films2016In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 34, no 4, p. 1-7Article in journal (Refereed)
    Abstract [en]

    Titanium chromium nitride (TiCrN) coatings with varying Cr content in two configurations, mono- and multilayer, were deposited on high speed steel substrates using a cylindrical cathodic arc physical vapor deposition technique. The physical, mechanical, and erosion behavior of the coatings were investigated. Among the monolayer coatings, the thicker Ti0.48Cr0.52N coatings yielded the best erosion resistance property. But with the increase in thickness, a considerable increase in residual stress is observed. Toward minimizing the stress accumulation, the effect of multilayering with periodic in situ heat treatment (after each 1 μm film growth) was studied by growing films in Ti0.52Cr0.48N/Ti0.40Cr0.60N bilayer configuration. A new approach based on % area of erosion damage for measuring relative wear rate of thin films has been proposed and implemented. The multilayer coatings exhibited superior erosion performance compared to the well-known erosion resistant TiN coatings that are in use for compressor blades from past few decades. Further, the erosion failure mechanisms in TiCrN coatings were also studied and found to be clearly different for mono- and multilayer configurations. The results reveal that the thicker multilayer TiCrN coatings (20 μm) exhibit promising choice for erosion resistance applications.

  • 99. Vassen, Robert
    et al.
    Cernuschi, Federico
    Rizzi, Gabriele
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Östergren, Lars
    Kloosterman, Arien
    Mevrel, Remy
    Feist, Jorg
    Nicholls, John
    Overview in the field of thermal barrier coatings including burner rig testing in the European Union2008In: Ceramics Japan, ISSN 0009-031X, Vol. 43, no 5, p. 371-382Article in journal (Other academic)
  • 100.
    Vuoristo, Petri
    et al.
    Tampere University of Technology.
    Nylén, Per
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Industrial and research activities in thermal spray technology in the Nordic region of Europe2007In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 16, no 4, p. 466-471Article in journal (Refereed)
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