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Goel, S., Shipley, J. & Joshi, S. V. (2023). Thermal post-treatment of additively manufactured components (1.ed.). In: Pederson, Robert, Andersson, Joel & Joshi, Shrikant V. (Ed.), Additive Manufacturing of High-Performance metallic Materials: (pp. 358-427). Elsevier
Open this publication in new window or tab >>Thermal post-treatment of additively manufactured components
2023 (English)In: Additive Manufacturing of High-Performance metallic Materials / [ed] Pederson, Robert, Andersson, Joel & Joshi, Shrikant V., Elsevier, 2023, 1., p. 358-427Chapter in book (Refereed)
Abstract [en]

Metal additive manufacturing (AM) processes have been receiving growing industrial attention in recent times for near net shape manufacture of complex parts with traditionally difficult-to-machine materials, such as high-performance super alloys and Titanium alloys. AM processing of these materials is especially promising for aerospace and other industrial sectors that value design flexibility, rapid production, and reduction in wastage of expensive feedstock. However, depending upon the specific AM technique employed, AM-built parts may be characterized by one or more of the following: defects, presence of undesirable phases, absence of desired hardening precipitates, anisotropy in properties, etc. Consequently, thermal post-treatment can be a crucial step in any robust production process aimed at ensuring that the AM-built components eventually meet critical service requirements. Depending upon the alloy in question, thermal post-treatments can comprise hot isostatic pressing and heat treatment. This chapter outlines the main drivers for thermal post-treatment in case of AM processed super alloys and Ti alloys, as well as the typical stages involved based on the alloy or application in question. The influence of each stage of post-treatment, as well as the associated time-temperature schedules, on microstructure, phase constitution, and mechanical properties is also discussed, using illustrative examples from AM-built Alloy 718 and Ti-6Al-4V.

Place, publisher, year, edition, pages
Elsevier, 2023 Edition: 1.
Keywords
Additive manufacturing; Powder bed fusion; Directed energy deposition; Superalloys; Titanium alloys; Hot isostatic pressing; Heat treatment; Defects; Microstructure; Phase constitution; Mechanical properties
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-21073 (URN)9780323918855 (ISBN)9780323913829 (ISBN)
Available from: 2023-12-14 Created: 2023-12-14 Last updated: 2024-01-12Bibliographically approved
Goel, S., Zaninelli, E., Gundgire, T., Ahlfors, M., Ojo, O., Klement, U. & Joshi, S. V. (2021). Microstructure evolution and mechanical response-based shortening of thermal post-treatment for electron beam melting (EBM) produced Alloy 718. Materials Science & Engineering: A, 820, Article ID 141515.
Open this publication in new window or tab >>Microstructure evolution and mechanical response-based shortening of thermal post-treatment for electron beam melting (EBM) produced Alloy 718
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2021 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 820, article id 141515Article in journal (Refereed) Published
Abstract [en]

Electron beam melting (EBM) produced Alloy 718 was subjected to thermal post-treatment involving hot isostatic pressing (HIPing) and heat treatment (HT). Subjecting the material to HIPing at 1120 degrees C led to significant densification. Study of microstructure evolution during HT (comprising of solution treatment and aging) showed possibility of significantly shortening the HT duration, particularly the time for two-step aging from the standard (8 h + 8 h) long cycle to possibly a shortened (4 h + 1 h) cycle. Another approach for shortening the post-treatment cycle by integrating the HIPing with HT inside the HIP vessel was also successfully implemented. The above observations were further substantiated by tensile response of the material subjected to the varied post-treatment cycles; out of all the post-treatments steps, tensile behaviour was observed to be mainly affected by the aging treatment. Further prospects for shortening the post-treatment protocol are also described, such as shortening of HIPing duration for the typical 4 h to 1 h cycle as well as possible elimination of solution treatment step from the entire post-treatment protocol specifically when prior HIPing is performed. Heat treatment with prior HIPing was found to be crucial for improving fatigue life, because subjecting EBM Alloy 718 to only HT, irrespective of the short or standard long protocol, rendered inferior fatigue response.

Place, publisher, year, edition, pages
Elsevier, 2021
Keywords
Additive manufacturing; Electron beam melting; Alloy 718; Post-treatment; Microstructure evolution; Mechanical properties
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-17272 (URN)10.1016/j.msea.2021.141515 (DOI)000668740700001 ()2-s2.0-85107286492 (Scopus ID)
Funder
Knowledge Foundation, 20160281
Available from: 2021-11-09 Created: 2021-11-09 Last updated: 2022-04-04Bibliographically approved
Ganvir, A., Goel, S., Govindarajan, S., Jahagirdar, A. R., Björklund, S., Klement, U. & Joshi, S. V. (2021). Tribological performance assessment of Al2O3-YSZ composite coatings deposited by hybrid powder-suspension plasma spraying. Surface & Coatings Technology, 409, 1-13, Article ID 126907.
Open this publication in new window or tab >>Tribological performance assessment of Al2O3-YSZ composite coatings deposited by hybrid powder-suspension plasma spraying
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2021 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 409, p. 1-13, article id 126907Article in journal (Refereed) Published
Abstract [en]

The advent of high-throughput plasma spray systems that allow axial feeding encourages the study of using liquid feedstock for various next-generation functional applications. The current study explores the benefit of such a plasma spray system to deposit hybrid powder-suspension Al2O3-YSZ ceramic matrix composite (CMC) coatings for tribological applications. The tribological performance of the hybrid processed CMC coatings was assessed using scratch, ball-on-plate wear and erosion tests and compared with that of monolithic powder-derived Al2O3 coatings. As-deposited and tribo-tested coatings were characterized using Scanning Electron Microscopy, X-ray Diffraction and Energy Dispersive Spectroscopy to analyse their microstructure and phase constitution. The results showed that the tribological performance of the hybrid powder-suspension Al2O3-YSZ CMC coating was significantly improved by enhancing the wear resistance under scratch, dry sliding ball-on-plate and erosion tests as compared to the conventional APS deposited monolithic Al2O3 coating. About 36% decrease in the dry sliding ball-on-plate specific wear rate and up to 50% decrease in the erosion wear rate was noted in the hybrid powder-suspension Al2O3-YSZ CMC coating as compared to the conventional APS deposited monolithic Al2O3 coating. The study concludes that the hybrid powder-suspension route can create CMC coatings with unique multi-length scale microstructures which can be attractive for combining different tribological attributes in the same coating system.

Place, publisher, year, edition, pages
Elsevier, 2021
Keywords
Hybrid; Axial plasma spray; Suspension; Powder; Tribology; Erosion; Scratch & wear
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-17236 (URN)10.1016/j.surfcoat.2021.126907 (DOI)000654045600066 ()2-s2.0-85100396405 (Scopus ID)
Funder
Swedish Energy Agency, P46393-1
Available from: 2021-12-16 Created: 2021-12-16 Last updated: 2021-12-16
Goel, S., Mehtani, H., Yao, S.-W., Samajdar, I., Klement, U. & Joshi, S. V. (2020). As-Built and Post-treated Microstructures of an Electron Beam Melting (EBM) Produced Nickel-Based Superalloy. Metallurgical and Materials Transactions. A, 51(12), 6546-6559
Open this publication in new window or tab >>As-Built and Post-treated Microstructures of an Electron Beam Melting (EBM) Produced Nickel-Based Superalloy
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2020 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 51, no 12, p. 6546-6559Article in journal (Refereed) Published
Abstract [en]

The microstructures of an electron beam melted (EBM) nickel-based superalloy (Alloy 718) were comprehensively investigated in as-built and post-treated conditions, with particular focus individually on the contour (outer periphery) and hatch (core) regions of the build. The hatch region exhibited columnar grains with strong texture in the build direction, while the contour region had a mix of columnar and equiaxed grains, with no preferred crystallographic texture. Both regions exhibited nearly identical hardness and carbide content. However, the contour region showed a higher number density of fine carbides compared to the hatch. The as-built material was subjected to two distinct post-treatments: (1) hot isostatic pressing (HIP) and (2) HIP plus heat treatment (HIP + HT), with the latter carried out as a single cycle inside the HIP vessel. Both post-treatments resulted in nearly an order of magnitude decrease in defect content in hatch and contour regions. HIP + HT led to grain coarsening in the contour, but did not alter the microstructure in the hatch region. Different factors that may be responsible for grain growth, such as grain size, grain orientation, grain boundary curvature and secondary phase particles, are discussed. The differences in carbide sizes in the hatch and contour regions appeared to decrease after post-treatment. After HIP + HT, similar higher hardness was observed in both the hatch and contour regions compared to the as-built material.

Keywords
Microstructures, Electron Beam Melting
National Category
Metallurgy and Metallic Materials
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-16004 (URN)10.1007/s11661-020-06037-z (DOI)000579330600002 ()2-s2.0-85092712120 (Scopus ID)
Funder
Knowledge Foundation, 20160281
Available from: 2020-11-04 Created: 2020-11-04 Last updated: 2021-04-29Bibliographically approved
Goel, S., Björklund, S., Curry, N., Govindarajan, S., Wiklund, U., Gaudiuso, C. & Joshi, S. V. (2020). Axial plasma spraying of mixed suspensions: A case study on processing, characteristics, and tribological behavior of Al2O3-YSZ coatings. Applied Sciences, 10(15), Article ID 5140.
Open this publication in new window or tab >>Axial plasma spraying of mixed suspensions: A case study on processing, characteristics, and tribological behavior of Al2O3-YSZ coatings
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2020 (English)In: Applied Sciences, E-ISSN 2076-3417, Vol. 10, no 15, article id 5140Article in journal (Refereed) Published
Abstract [en]

Thermal spraying deploying liquid feedstock offers an exciting opportunity to obtain coatings with characteristics vastly different from those produced using conventional spray-grade powders. The most extensively investigated variant of this technique is Suspension Plasma Spraying (SPS), which utilizes a suspension of fine powders in an appropriate medium. The relatively recent advent of axial feed capable plasma spray systems can enable higher throughputs during SPS, provides the possibility for spraying with longer stand-off distances, and also permit the use of suspensions with higher solid loading. The present work investigates axial plasma sprayed coatings produced using a mixed suspension of fine (submicron or nano-sized) powders of Al2O3 and YSZ as a case study. Deposition of the mixed suspension using axial injection plasma spraying, comprehensive evaluation of characteristics of the resulting coatings, and assessment of their tribological behavior were of particular interest. Evaluation of surface morphology, microstructure, and hardness of the coatings reveals that axial SPS of mixed suspensions provides an exciting pathway to realize finely structured multi-constituent coatings using suspensions with as high as 40 wt. % solid loading. The study of scratch, dry sliding wear, and erosion behavior also specifically shows that the addition of YSZ in the Al2O3 matrix can improve the tribological properties of the coating. © 2020 by the authors.

Place, publisher, year, edition, pages
MDPI AG, 2020
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:hv:diva-15748 (URN)10.3390/app10155140 (DOI)000559142800001 ()2-s2.0-85088862849 (Scopus ID)
Available from: 2020-08-26 Created: 2020-08-26 Last updated: 2021-04-27
Goel, S., Bourreau, K., Olsson, J., Klement, U. & Joshi, S. V. (2020). Can Appropriate Thermal Post-Treatment Make Defect Content in as-Built Electron Beam Additively Manufactured Alloy 718 Irrelevant?. Materials, 13(3), Article ID 536.
Open this publication in new window or tab >>Can Appropriate Thermal Post-Treatment Make Defect Content in as-Built Electron Beam Additively Manufactured Alloy 718 Irrelevant?
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2020 (English)In: Materials, E-ISSN 1996-1944, Vol. 13, no 3, article id 536Article in journal (Refereed) Published
Abstract [en]

Electron beam melting (EBM) is gaining rapid popularity for production of complex customized parts. For strategic applications involving materials like superalloys (e.g., Alloy 718), post-treatments including hot isostatic pressing (HIPing) to eliminate defects, and solutionizing and aging to achieve the desired phase constitution are often practiced. The present study specifically explores the ability of the combination of the above post-treatments to render the as-built defect content in EBM Alloy 718 irrelevant. Results show that HIPing can reduce defect content from as high as 17% in as-built samples (intentionally generated employing increased processing speeds in this illustrative proof-of-concept study) to <0.3%, with the small amount of remnant defects being mainly associated with oxide inclusions. The subsequent solution and aging treatments are also found to yield virtually identical phase distribution and hardness values in samples with vastly varying as-built defect contents. This can have considerable implications in contributing to minimizing elaborate process optimization efforts as well as slightly enhancing production speeds to promote industrialization of EBM for applications that demand the above post-treatments.

Keywords
additive manufacturing, electron beam melting, defects, microstructure, hardness, alloy 718, hot isostatic pressing, post-treatment
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:hv:diva-14926 (URN)10.3390/ma13030536 (DOI)000515503100043 ()2-s2.0-85079600396 (Scopus ID)
Funder
Knowledge Foundation, 20160281
Available from: 2020-01-30 Created: 2020-01-30 Last updated: 2024-07-04
Zafer, Y. E., Goel, S., Ganvir, A., Jansson, A. & Joshi, S. V. (2020). Encapsulation of Electron Beam Melting Produced Alloy 718 to Reduce Surface Connected Defects by Hot Isostatic Pressing. Materials, 13(5), Article ID 1226.
Open this publication in new window or tab >>Encapsulation of Electron Beam Melting Produced Alloy 718 to Reduce Surface Connected Defects by Hot Isostatic Pressing
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2020 (English)In: Materials, E-ISSN 1996-1944, Vol. 13, no 5, article id 1226Article in journal (Refereed) Published
Abstract [en]

Defects in electron beam melting (EBM) manufactured Alloy 718 are inevitable to some extent, and are of concern as they can degrade mechanical properties of the material. Therefore, EBM-manufactured Alloy 718 is typically subjected to post-treatment to improve the properties of the as-built material. Although hot isostatic pressing (HIPing) is usually employed to close the defects, it is widely known that HIPing cannot close open-to-surface defects. Therefore, in this work, a hypothesis is formulated that if the surface of the EBM-manufactured specimen is suitably coated to encapsulate the EBM-manufactured specimen, then HIPing can be effective in healing such surface-connected defects. The EBM-manufactured Alloy 718 specimens were coated by high-velocity air fuel (HVAF) spraying using Alloy 718 powder prior to HIPing to evaluate the above approach. X-ray computed tomography (XCT) analysis of the defects in the same coated sample before and after HIPing showed that some of the defects connected to the EBM specimen surface were effectively encapsulated by the coating, as they were closed after HIPing. However, some of these surface-connected defects were retained. The reason for such remnant defects is attributed to the presence of interconnected pathways between the ambient and the original as-built surface of the EBM specimen, as the specimens were not coated on all sides. These pathways were also exaggerated by the high surface roughness of the EBM material and could have provided an additional path for argon infiltration, apart from the uncoated sides, thereby hindering complete densification of the specimen during HIPing.

National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:hv:diva-15061 (URN)10.3390/ma13051226 (DOI)000524060200204 ()2-s2.0-85092028472 (Scopus ID)
Available from: 2020-03-25 Created: 2020-03-25 Last updated: 2024-07-04
Goel, S., Zaninelli, E., Gårdstam, J., Klement, U. & Joshi, S. V. (2020). Microstructure evolution-based design of thermal post-treatments for EBM-built Alloy 718. Journal of Materials Science, 56(2), 5250-5268
Open this publication in new window or tab >>Microstructure evolution-based design of thermal post-treatments for EBM-built Alloy 718
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2020 (English)In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 56, no 2, p. 5250-5268Article in journal (Refereed) Published
Abstract [en]

Alloy 718 samples were fabricated by electron beam melting (EBM) additive manufacturing process. The work focused on systematic investigation of response of the material to various thermal post-treatments, involving hot isostatic pressing (HIPing), solution treatment (ST) and two-step aging, to tailor post-treatment procedure for EBM-built Alloy 718. Results showed that HIPing at lowered temperature can be used for attaining desired defect closure while preserving grain size. Subjecting the material to ST, with or without prior HIPing, mainly caused precipitation of δ phase at the grain boundaries with prior HIPing decreasing the extent of δ phase precipitation. Moreover, results suggest that the utility of ST, with prior HIPing, could be dictated by the need to achieve a certain δ phase content, as the typically targeted homogenization after ST had already been achieved through HIPing. Detailed investigation of microstructural evolution during subsequent aging with and without prior HIPing showed that a significantly shortened aging treatment (‘4 + 1’ h), compared to the ‘standard’ long treatment (‘8 + 8’ h) traditionally developed for conventionally produced Alloy 718, might be realizable. These results can have significant techno-economic implications in designing tailored post-treatments for EBM-built Alloy 718.

Keywords
Alloy 718, Electronic Beam Mealting
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-16131 (URN)10.1007/s10853-020-05595-2 (DOI)000597436100001 ()2-s2.0-85097502396 (Scopus ID)
Available from: 2020-12-17 Created: 2020-12-17 Last updated: 2021-04-30
Goel, S., Neikter, M., Capek, J., Polatidis, E., Colliander, M. H., Joshi, S. V. & Pederson, R. (2020). Residual stress determination by neutron diffraction in powder bed fusion-built Alloy 718: Influence of process parameters and post-treatment. Materials & design, 195, Article ID 109045.
Open this publication in new window or tab >>Residual stress determination by neutron diffraction in powder bed fusion-built Alloy 718: Influence of process parameters and post-treatment
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2020 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 195, article id 109045Article in journal (Refereed) Published
Abstract [en]

Alloy 718 is a nickel-based superalloy that is widely used as a structural material for high-temperature applications. One concern that arises when Alloy 718 is manufactured using powder bed fusion (PBF) is that residual stresses appear due to the high thermal gradients. These residual stresses can be detrimental as they can degrade mechanical properties and distort components. In this work, residual stresses in PBF built Alloy 718, using both electron and laser energy sources, were measured by neutron diffraction. The effects of process parameters and thermal post-treatments were studied. The results show that thermal post-treatments effectively reduce the residual stresses present in the material. Moreover, the material built with laser based PBF showed a higher residual stress compared to the material built with electron-beam based PBF. The scanning strategy with the lower amount of residual stresses in case of laser based PBF was the chessboard strategy compared to the bi-directional raster strategy. In addition, the influence of measured and calculated lattice spacing (d0) on the evaluated residual stresses was investigated. © 2020 The Authors

Keywords
High temperature applications; Nickel alloys, Influence of process parameters; Lattice spacing; Nickel- based superalloys; Post treatment; Process parameters; Residual stress determination; Scanning strategies; Thermal post-treatments, Residual stresses
National Category
Manufacturing, Surface and Joining Technology Composite Science and Engineering
Identifiers
urn:nbn:se:hv:diva-15751 (URN)10.1016/j.matdes.2020.109045 (DOI)000576530800010 ()2-s2.0-85089396801 (Scopus ID)
Funder
Knowledge Foundation, 20160281EU, Horizon 2020, 701647
Available from: 2020-08-26 Created: 2020-08-26 Last updated: 2021-04-27Bibliographically approved
Gundgire, T., Goel, S., Klement, U. & Joshi, S. V. (2020). Response of different electron beam melting produced Alloy 718 microstructures to thermal post-treatments. Materials Characterization, 167, Article ID 110498.
Open this publication in new window or tab >>Response of different electron beam melting produced Alloy 718 microstructures to thermal post-treatments
2020 (English)In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 167, article id 110498Article in journal (Refereed) Published
Abstract [en]

Electron beam melting (EBM) was used to produce Alloy 718 specimens with different microstructures (columnar, equiaxed and a combination thereof) by varying the process parameters. The present study aimed at assessing the response of such varying as-built microstructures to identical thermal post-treatments, which included hot isostatic pressing (HIPing) followed by heat treatment involving solution treatment and aging. The effect of these treatments on defect content, grain structure, hardness and phase constitution in the specimens was specifically analysed. Despite differences in defect content of as-built specimens with distinct microstructures, HIPing was effective in closing defects leading to samples exhibiting similar density. After HIPing, grains with equiaxed morphology or columnar grains with lower aspect ratio showed higher tendency for grain growth in comparison to the columnar grains with higher aspect ratio. The various factors affecting the stability of grains during HIPing of builds with distinct microstructures were investigated. These factors include texture, grain size, and secondary phase particles. The carbide sizes in the different as-built samples varied but were found to be largely unaffected by the post-treatments. Solution treatment following HIPing led to greater precipitation of grain boundary ÎŽ phase in regions with coarser grains than the smaller ones. After HIPing and heat treatment, all specimens exhibited similar precipitation of γ″ phase regardless of their grain morphology in the as-built condition. © 2020 The Author(s)

Keywords
Carbides; Electron beam melting; Electron beams; Grain boundaries; Grain growth; Grain size and shape; Heat treatment; Hot isostatic pressing; Morphology; Textures, Coarser grains; Defect contents; Grain morphologies; Phase constitution; Process parameters; Secondary phase particles; Solution treatments; Thermal post-treatments, Aspect ratio, Additive manufacturing, Alloy 718, Columnar, Equiaxed, Post-Treatment
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:hv:diva-15744 (URN)10.1016/j.matchar.2020.110498 (DOI)000558805700044 ()2-s2.0-85087961064 (Scopus ID)
Funder
Knowledge Foundation, 20160281
Available from: 2020-08-25 Created: 2020-08-25 Last updated: 2020-11-04Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5676-7903

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