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Asala, G., Andersson, J. & Ojo, O. A. (2019). A study of the dynamic impact behaviour of IN 718 and ATI 718Plus® superalloys. Philosophical Magazine, 99(4), 419-437
Open this publication in new window or tab >>A study of the dynamic impact behaviour of IN 718 and ATI 718Plus® superalloys
2019 (English)In: Philosophical Magazine, ISSN 1478-6435, E-ISSN 1478-6443, Vol. 99, no 4, p. 419-437Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Taylor and Francis Ltd., 2019
Keywords
Deformation, Dynamics, Iron alloys, Mechanical properties, Nickel alloys, Scanning electron microscopy, Shear bands, Strain hardening, Superalloys, Transmission electron microscopy, Twinning, Compositional modification, Damage, Deformation properties, Deformation temperatures, Heat treatment conditions, Stacking fault energies, Strain hardening and strain rate sensitivity, Strengthening mechanisms, Strain rate
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13177 (URN)10.1080/14786435.2018.1540891 (DOI)000455480300002 ()2-s2.0-85056162234 (Scopus ID)
Note

Published online: 07 Nov 2018

Funder: Natural Sciences and Engineering Research Council of Canada

Available from: 2018-12-03 Created: 2018-12-03 Last updated: 2019-02-04Bibliographically approved
Asala, G., Andersson, J. & Ojo, O. A. (2019). Analysis and constitutive modelling of high strain rate deformation behaviour of wire-arc additive-manufactured ATI 718Plus superalloy. The International Journal of Advanced Manufacturing Technology, 3(1-4), 1419-1431
Open this publication in new window or tab >>Analysis and constitutive modelling of high strain rate deformation behaviour of wire-arc additive-manufactured ATI 718Plus superalloy
2019 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 3, no 1-4, p. 1419-1431Article in journal (Refereed) Published
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.

Keywords
3D printers, Additives, Constitutive models, Deformation, Deposits, Machinability, Machining, Mean square error, Metallurgy, Nickel alloys, Plastic flow, Solidification, Superalloys, Wire, Deformation microstructure, Finite element simulations, Heterogeneous distributions, High strain rate deformation, High strain rates, Machinability assessment, Ni-based superalloys, Root mean square errors, Strain rate
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13848 (URN)10.1007/s00170-019-03616-2 (DOI)000475921300105 ()2-s2.0-85064476747 (Scopus ID)
Note

Funders; Natural Sciences and Engineering Research Council of Canada

Available from: 2019-05-24 Created: 2019-05-24 Last updated: 2019-10-16Bibliographically approved
Karimi Neghlani, P., Sadeghi, E., Ålgårdh, J. & Andersson, J. (2019). EBM-manufactured single tracks of Alloy 718: Influence of energy input and focus offset on geometrical and microstructural characteristics. Materials Characterization, 148, 88-99
Open this publication in new window or tab >>EBM-manufactured single tracks of Alloy 718: Influence of energy input and focus offset on geometrical and microstructural characteristics
2019 (English)In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 148, p. 88-99Article in journal (Refereed) Published
Abstract [en]

Electron beam melting-powder bed fusion (EBM-PBF) is an additive manufacturing process, which is able to produce parts in layer-by-layer fashion from a 3D model data. Currently application of this technology in parts manufacturing with high geometrical complexity has acquired growing interest in industry. To recommend the EBM process into industry for manufacturing parts, improved mechanical properties of final part must be obtained. Such properties highly depend on individual single melted track and single layer. In EBM, interactions between the electron beam, powder, and solid underlying layer affect the geometrical (e.g., re-melt depth, track width, contact angle, and track height) and microstructural (e.g., grain structure, and primary dendrite arm spacing) characteristics of the melted tracks. The core of the present research was to explore the influence of linear energy input parameters in terms of beam scanning speed, beam current as well as focus offset and their interactions on the geometry and microstructure of EBM-manufactured single tracks of Alloy 718. Increased scanning speed led to lower linear energy input values (<0.9 J/mm) in an specific range of the focus offset (0–10 mA) which resulted in instability, and discontinuity of the single tracks as well as balling effect. Decreasing the scanning speed and increasing the beam current resulted in higher melt pool depth and width. By statistical evaluations, the most influencing parameters on the geometrical features were primarily the scanning speed, and secondly the beam current. Primary dendrite arm spacing (PDAS) slightly decreased by increasing the scanning speed using lower beam current values as the linear energy input decreased. By increasing the linear energy input, the chance of more equiaxed grain formation was high, however, at lower linear energy input, mainly columnar grains were observed. The lower focus offset values resulted in more uniform grains along the 〈001〉 crystallographic direction. © 2018 Elsevier Inc. 

Keywords
3D printers; Contact angle; Dendrites (metallography); Design of experiments; Electron beam melting; Electron beams; Scanning; Speed, Alloy 718; Geometrical characteristics; Powder bed; Single-tracks; Solidified microstructures, Geometry
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13365 (URN)10.1016/j.matchar.2018.11.033 (DOI)2-s2.0-85058512738 (Scopus ID)
Funder
European Regional Development Fund (ERDF)Knowledge Foundation
Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2019-02-28Bibliographically approved
Asala, G., Andersson, J. & Ojo, O. A. (2019). Hot corrosion behaviour of wire-arc additive manufactured Ni-based superalloy ATI 718Plus®. Corrosion Science, 158, Article ID 108086.
Open this publication in new window or tab >>Hot corrosion behaviour of wire-arc additive manufactured Ni-based superalloy ATI 718Plus®
2019 (English)In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 158, article id 108086Article in journal (Refereed) Published
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

Keywords
3D printers; Additives; Corrosion resistance; Corrosion resistant alloys; Corrosive effects; Electron microscopes; Electron microscopy; Heat resistance; Nickel alloys; Superalloys; Transmission electron microscopy, ATI 718Plus; Hot corrosion; Metal additives; Ni-based superalloys; WAAM, High temperature corrosion
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14476 (URN)10.1016/j.corsci.2019.07.010 (DOI)000483638900016 ()2-s2.0-85068854753 (Scopus ID)
Note

Funders: Natural Sciences and Engineering Research Council of Canada (NSERC)

Available from: 2019-10-01 Created: 2019-10-01 Last updated: 2019-11-12Bibliographically approved
Raza, T., Hurtig, K., Asala, G., Andersson, J., Svensson, L.-E. & Ojo, O. A. (2019). Influence of Heat Treatments on Heat Affected Zone Cracking of Gas Tungsten Arc Welded Additive Manufactured Alloy 718. Metals, 9(8), Article ID 881.
Open this publication in new window or tab >>Influence of Heat Treatments on Heat Affected Zone Cracking of Gas Tungsten Arc Welded Additive Manufactured Alloy 718
Show others...
2019 (English)In: Metals, Vol. 9, no 8, article id 881Article in journal (Refereed) Published
Abstract [en]

The weldability of additive manufactured Alloy 718 was investigated in various heat-treated conditions. The microstructure of the base metal was examined in detail in order to understand the effect of different pre-weld heat treatments; i.e., solution, solution and aging, and hot isostatic pressing. After welding, the variation in total crack lengths, maximum crack length and the total number of cracks in the heat affected zone (HAZ) were used as criteria for the cracking susceptibility of each material condition where wrought Alloy 718 was used as the reference material. Selective laser melting (SLM) manufactured Alloy 718 was susceptible to HAZ cracking in all material conditions. Total crack lengths in HAZ were highest in the SLM as-built condition and lowest in the SLM hot isostatic pressed condition. The cracks that were found in the HAZ of the welded materials consisted of liquation cracks, with eutectic product surrounding the cracks, as well as cracks from which liquation products were absent.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
selective laser melting; Alloy 718; heat treatments; gas tungsten arc welding; heat affected zone cracking
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14595 (URN)10.3390/met9080881 (DOI)000484510000071 ()2-s2.0-85073280907 (Scopus ID)
Available from: 2019-10-16 Created: 2019-10-16 Last updated: 2019-11-13
Sadeghi, E., Karimi Neghlani, P., Momeni, S., Seifi, M., Eklund, A. & Andersson, J. (2019). Influence of thermal post treatments on microstructure and oxidation behavior of EB-PBF manufactured Alloy 718. Materials Characterization, 150, 236-251
Open this publication in new window or tab >>Influence of thermal post treatments on microstructure and oxidation behavior of EB-PBF manufactured Alloy 718
Show others...
2019 (English)In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 150, p. 236-251Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Additive manufacturing, Electron beam powder bed fusion, Alloy 718, Oxidation, Heat treatment, Hot isostatic pressing
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13740 (URN)10.1016/j.matchar.2019.02.016 (DOI)000462420900027 ()2-s2.0-85062014143 (Scopus ID)
Funder
Knowledge Foundation
Available from: 2019-03-21 Created: 2019-03-21 Last updated: 2019-05-10Bibliographically approved
Draxler, J., Edberg, J., Andersson, J. & Lindgren, L.-E. -. (2019). Modeling and simulation of weld solidification cracking part I: A pore-based crack criterion. Welding in the World, 63(5), 1489-1502
Open this publication in new window or tab >>Modeling and simulation of weld solidification cracking part I: A pore-based crack criterion
2019 (English)In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, no 5, p. 1489-1502Article in journal (Refereed) Published
Abstract [en]

Several advanced alloy systems are susceptible to weld solidification cracking. One example is nickel-based superalloys, which are commonly used in critical applications such as aerospace engines and nuclear power plants. Weld solidification cracking is often expensive to repair and, if not repaired, can lead to catastrophic failure. This study, presented in three papers, presents an approach for simulating weld solidification cracking applicable to large-scale components. The results from finite element simulation of welding are post-processed and combined with models of metallurgy, as well as the behavior of the liquid film between the grain boundaries, in order to estimate the risk of crack initiation. The first paper in this study describes the crack criterion for crack initiation in a grain boundary liquid film. The second paper describes the model for computing the pressure and the thickness of the grain boundary liquid film, which are required to evaluate the crack criterion in paper 1. The third and final paper describes the application of the model to Varestraint tests of alloy 718. The derived model can fairly well predict crack locations, crack orientations, and crack widths for the Varestraint tests. The importance of liquid permeability and strain localization for the predicted crack susceptibility in Varestraint tests is shown. © 2019, The Author(s).

Keywords
Crack initiation; Grain boundaries; Liquid films; Nickel alloys; Nuclear fuels; Nuclear power plants; Paper; Risk perception; Solidification; Welding; Welds, Alloy 718; Catastrophic failures; Crack susceptibilities; Critical applications; Finite element simulations; Hot cracking; Nickel- based superalloys; Solidification cracking, Cracks
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hv:diva-14477 (URN)10.1007/s40194-019-00760-x (DOI)000482459300029 ()2-s2.0-85068801005 (Scopus ID)
Funder
Vinnova, 2013-01140Swedish Armed Forces, 2017-04837
Note

Funders: FMV;

Available from: 2019-10-01 Created: 2019-10-01 Last updated: 2019-11-15Bibliographically approved
Draxler, J., Edberg, J., Andersson, J. & Lindgren, L.-E. -. (2019). Modeling and simulation of weld solidification cracking part II: A model for estimation of grain boundary liquid pressure in a columnar dendritic microstructure. Welding in the World, 63(5), 1503-1519
Open this publication in new window or tab >>Modeling and simulation of weld solidification cracking part II: A model for estimation of grain boundary liquid pressure in a columnar dendritic microstructure
2019 (English)In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, no 5, p. 1503-1519Article in journal (Refereed) Published
Abstract [en]

Several advanced alloy systems are susceptible to weld solidification cracking. One example is nickel-based superalloys, which are commonly used in critical applications such as aerospace engines and nuclear power plants. Weld solidification cracking is often expensive to repair, and if not repaired, can lead to catastrophic failure. This study, presented in three papers, presents an approach for simulating weld solidification cracking applicable to large-scale components. The results from finite element simulation of welding are post-processed and combined with models of metallurgy, as well as the behavior of the liquid film between the grain boundaries, in order to estimate the risk of crack initiation. The first paper in this study describes the crack criterion for crack initiation in a grain boundary liquid film. The second paper describes the model for computing the pressure and the thickness of the grain boundary liquid film, which are required to evaluate the crack criterion in paper 1. The third and final paper describes the application of the model to Varestraint tests of Alloy 718. The derived model can fairly well predict crack locations, crack orientations, and crack widths for the Varestraint tests. The importance of liquid permeability and strain localization for the predicted crack susceptibility in Varestraint tests is shown. © 2019, The Author(s).

Keywords
Crack initiation; Grain boundaries; Liquid films; Nickel alloys; Nuclear fuels; Nuclear power plants; Paper; Risk perception; Solidification; Welding; Welds, Alloy 718; Crack susceptibilities; Critical applications; Dendritic microstructure; Finite element simulations; Hot cracking; Nickel- based superalloys; Solidification cracking, Cracks
National Category
Metallurgy and Metallic Materials Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-14461 (URN)10.1007/s40194-019-00761-w (DOI)000482459300030 ()2-s2.0-85068150806 (Scopus ID)
Funder
Swedish Armed Forces, 2013-01140Vinnova, 2017-04837
Note

Funders:GKN

Available from: 2019-10-01 Created: 2019-10-01 Last updated: 2019-11-15Bibliographically approved
Draxler, J., Edberg, J., Andersson, J. & Lindgren, L.-E. -. (2019). Modeling and simulation of weld solidification cracking part III: Simulation of solidification cracking in Varestraint tests of alloy 718. Welding in the World, 63(6), 1883-1901
Open this publication in new window or tab >>Modeling and simulation of weld solidification cracking part III: Simulation of solidification cracking in Varestraint tests of alloy 718
2019 (English)In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, no 6, p. 1883-1901Article in journal (Refereed) Published
Abstract [en]

Several advanced alloy systems are susceptible to weld solidification cracking. One example is nickel-based superalloys, which are commonly used in critical applications such as aerospace engines and nuclear power plants. Weld solidification cracking is often expensive to repair, and if not repaired, can lead to catastrophic failure. This study, presented in three papers, presents an approach for simulating weld solidification cracking applicable to large-scale components. The results from finite element simulation of welding are post-processed and combined with models of metallurgy, as well as the behavior of the liquid film between the grain boundaries, in order to estimate the risk of crack initiation. The first paper in this study describes the crack criterion for crack initiation in a grain boundary liquid film. The second paper describes the model required to compute the pressure and thickness of the liquid film required in the crack criterion. The third and final paper describes the application of the model to Varestraint tests of alloy 718. The derived model can fairly well predict crack locations, crack orientations, and crack widths for the Varestraint tests. The importance of liquid permeability and strain localization for the predicted crack susceptibility in Varestraint tests is shown. © 2019, The Author(s).

Place, publisher, year, edition, pages
Springer Verlag, 2019
Keywords
Crack initiation; Grain boundaries; Liquid films; Nickel alloys; Nuclear fuels; Nuclear power plants; Paper; Risk perception; Solidification; Welding; Welds, Alloy 718; Catastrophic failures; Crack susceptibilities; Critical applications; Finite element simulations; Hot cracking; Nickel- based superalloys; Solidification cracking, Cracks
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14471 (URN)10.1007/s40194-019-00784-3 (DOI)2-s2.0-85071447851 (Scopus ID)
Funder
Swedish Armed Forces, 2013-01140Vinnova, 2017-04837
Note

Funders: FMV; GKN

Available from: 2019-10-01 Created: 2019-10-01 Last updated: 2019-11-15Bibliographically approved
Raza, T., Andersson, J. & Svensson, L.-E. (2019). Varestraint testing of selective laser additive manufactured alloy 718: influence of grain orientation. Metals, 9(10), Article ID 1113.
Open this publication in new window or tab >>Varestraint testing of selective laser additive manufactured alloy 718: influence of grain orientation
2019 (English)In: Metals, ISSN 2075-4701, Vol. 9, no 10, article id 1113Article in journal (Refereed) Published
Abstract [en]

The effect of grain orientation on hot cracking susceptibility of selective laser additive manufactured Alloy 718 was investigated by Varestraint testing. Electron backscattered diffraction showed that cracks in heat affected zone (HAZ) of the welded samples occurred in high angle grain boundaries. The extent of HAZ cracking was smaller in samples tested parallel to the elongated grain orientation and larger in samples transverse to the elongated grain orientation. However, for solidification cracking in the weld metal, no significant difference with respect to grain orientation in the base metal was found. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.

Place, publisher, year, edition, pages
MDPI AG, 2019
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14708 (URN)10.3390/met9101113 (DOI)2-s2.0-85074226227 (Scopus ID)
Funder
Vinnova
Available from: 2019-11-14 Created: 2019-11-14 Last updated: 2019-11-14
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-9065-0741

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