Cascading of the as-built microstructure through heat treatment and its role on the tensile properties of laser powder bed fused Inconel 718

The microstructures and mechanical properties of the Ni based superalloy, Inconel 718 (IN718), which was additively manufactured using the laser beam powder bed fusion (LB-PBF) technique in the as-built (AB) and heat treated (HT) conditions were investigated, with emphasis on the microstructural evo...

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Main Authors: Radhakrishnan, R. Jayaraj, Kumar, Punit, Seet, Hang Li, Nai, Sharon Mui Ling, Wang, Pei, Ramamurty, Upadrasta
Other Authors: School of Mechanical and Aerospace Engineering
Format: Article
Language:English
Published: 2022
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Online Access:https://hdl.handle.net/10356/162365
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-1623652022-10-17T03:31:54Z Cascading of the as-built microstructure through heat treatment and its role on the tensile properties of laser powder bed fused Inconel 718 Radhakrishnan, R. Jayaraj Kumar, Punit Seet, Hang Li Nai, Sharon Mui Ling Wang, Pei Ramamurty, Upadrasta School of Mechanical and Aerospace Engineering Institute of Materials Research and Engineering, A*STAR Singapore Institute of Manufacturing Technology Engineering::Materials Heat Treatment Crystallographic Texture The microstructures and mechanical properties of the Ni based superalloy, Inconel 718 (IN718), which was additively manufactured using the laser beam powder bed fusion (LB-PBF) technique in the as-built (AB) and heat treated (HT) conditions were investigated, with emphasis on the microstructural evolution from the AB to HT conditions and, in turn, on the tensile properties. Optimized LB-PBF parameters in two different processing instruments led to distinct textures in the AB alloys, which, in turn, impart diverging combinations of strength-ductility properties. These variations are rationalized by recourse to an analysis of the effective mean free path for dislocations within the solidification cell structures. Amongst the five different heat treatment schedules examined, one set led to the retention of as-built grain morphology and texture with the formation of the δ phase that is oriented at either ±45° to build direction in the alloy with 〈100〉 texture or at 0/ ± 90 ° in the alloy with 〈110〉 texture. The second set of heat treatments led to complete recrystallization, and hence loss of as-built microstructural signatures, with no δ phase. The critical role of δ phase in determining the grain growth kinetics and subsequently the anisotropy in mechanical properties of heat treated IN718 was elucidated. The absence of δ phase was found to enhance both strength and ductility, while its occurrence in the alloy with 〈110〉 texture along the build direction reduces ductility markedly. Implications of these results in terms of developing and designing the processing strategies of LB-PBF Inconel 718 with tailored microstructures and good mechanical properties are discussed. Agency for Science, Technology and Research (A*STAR) This research is supported by Agency for Science, Technology and Research (A∗STAR) of Singapore via the Structural Metals Alloys Program (No. A18B1b0061). 2022-10-17T03:31:54Z 2022-10-17T03:31:54Z 2022 Journal Article Radhakrishnan, R. J., Kumar, P., Seet, H. L., Nai, S. M. L., Wang, P. & Ramamurty, U. (2022). Cascading of the as-built microstructure through heat treatment and its role on the tensile properties of laser powder bed fused Inconel 718. Materialia, 21, 101272-. https://dx.doi.org/10.1016/j.mtla.2021.101272 2589-1529 https://hdl.handle.net/10356/162365 10.1016/j.mtla.2021.101272 2-s2.0-85119956302 21 101272 en A18B1b0061 Materialia © 2021 Acta Materialia Inc. Published by Elsevier B.V. All rights reserved.
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic Engineering::Materials
Heat Treatment
Crystallographic Texture
spellingShingle Engineering::Materials
Heat Treatment
Crystallographic Texture
Radhakrishnan, R. Jayaraj
Kumar, Punit
Seet, Hang Li
Nai, Sharon Mui Ling
Wang, Pei
Ramamurty, Upadrasta
Cascading of the as-built microstructure through heat treatment and its role on the tensile properties of laser powder bed fused Inconel 718
description The microstructures and mechanical properties of the Ni based superalloy, Inconel 718 (IN718), which was additively manufactured using the laser beam powder bed fusion (LB-PBF) technique in the as-built (AB) and heat treated (HT) conditions were investigated, with emphasis on the microstructural evolution from the AB to HT conditions and, in turn, on the tensile properties. Optimized LB-PBF parameters in two different processing instruments led to distinct textures in the AB alloys, which, in turn, impart diverging combinations of strength-ductility properties. These variations are rationalized by recourse to an analysis of the effective mean free path for dislocations within the solidification cell structures. Amongst the five different heat treatment schedules examined, one set led to the retention of as-built grain morphology and texture with the formation of the δ phase that is oriented at either ±45° to build direction in the alloy with 〈100〉 texture or at 0/ ± 90 ° in the alloy with 〈110〉 texture. The second set of heat treatments led to complete recrystallization, and hence loss of as-built microstructural signatures, with no δ phase. The critical role of δ phase in determining the grain growth kinetics and subsequently the anisotropy in mechanical properties of heat treated IN718 was elucidated. The absence of δ phase was found to enhance both strength and ductility, while its occurrence in the alloy with 〈110〉 texture along the build direction reduces ductility markedly. Implications of these results in terms of developing and designing the processing strategies of LB-PBF Inconel 718 with tailored microstructures and good mechanical properties are discussed.
author2 School of Mechanical and Aerospace Engineering
author_facet School of Mechanical and Aerospace Engineering
Radhakrishnan, R. Jayaraj
Kumar, Punit
Seet, Hang Li
Nai, Sharon Mui Ling
Wang, Pei
Ramamurty, Upadrasta
format Article
author Radhakrishnan, R. Jayaraj
Kumar, Punit
Seet, Hang Li
Nai, Sharon Mui Ling
Wang, Pei
Ramamurty, Upadrasta
author_sort Radhakrishnan, R. Jayaraj
title Cascading of the as-built microstructure through heat treatment and its role on the tensile properties of laser powder bed fused Inconel 718
title_short Cascading of the as-built microstructure through heat treatment and its role on the tensile properties of laser powder bed fused Inconel 718
title_full Cascading of the as-built microstructure through heat treatment and its role on the tensile properties of laser powder bed fused Inconel 718
title_fullStr Cascading of the as-built microstructure through heat treatment and its role on the tensile properties of laser powder bed fused Inconel 718
title_full_unstemmed Cascading of the as-built microstructure through heat treatment and its role on the tensile properties of laser powder bed fused Inconel 718
title_sort cascading of the as-built microstructure through heat treatment and its role on the tensile properties of laser powder bed fused inconel 718
publishDate 2022
url https://hdl.handle.net/10356/162365
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