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Homogenization of Inconel 718 Made by Additive Manufacturing and Suction Casting

Gargani, Matthew (2019) Homogenization of Inconel 718 Made by Additive Manufacturing and Suction Casting. Master's Thesis, University of Pittsburgh. (Unpublished)

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Inconel 718 is considered a promising candidate for production via additive manufacturing (AM) due to its excellent weldability. However, compared to traditional manufacturing methods, less attention has been paid to developing heat treatments of AM components. To better design the post-processing of Inconel 718 made by AM techniques, the CALPHAD (Calculation of Phase Diagrams) method is applied to study the phase equilibrium, metastable phase behavior, and phase transformations during the homogenization process of Inconel 718. Scanning electron microscopy, energy dispersive X-ray spectroscopy, and electron backscatter diffraction are employed to study the microstructure evolution of different samples supporting the CALPHAD model prediction. Suction cast samples are also investigated to provide a benchmark for comparison. The calculations and experiments are in agreement that homogenization occurs more rapidly in samples made by laser-powder bed fusion than by suction casting. Intriguingly, significant grain growth occurs at the homogenization temperature of 1,180°C for the suction cast samples, but only recrystallization and minor grain growth occurs for the AM samples. AM Inconel 718 samples show promise for reducing the time required for homogenization heat treatment. It is observed that the detrimental Laves phase dissolves in AM samples within 20 minutes due to the smaller grain size and less pronounced Nb segregation than suction cast samples. The new findings confirm that post-processing optimization for AM Inconel 718 components are essential.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Gargani, Matthewtheoneandonly.mrgargani@gmail.commag3610000-0002-2902-2647
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee MemberGleeson, Brianbmg36@pitt.edubmg36
Committee MemberLee, Jung-Kunjul37@pitt.edujul37
Committee ChairXiong, Weiweixiong@pitt.eduweixiong
Thesis AdvisorXiong, Weiweixiong@pitt.eduweixiong
Date: 18 June 2019
Date Type: Publication
Defense Date: 26 March 2019
Approval Date: 18 June 2019
Submission Date: 19 March 2019
Access Restriction: 1 year -- Restrict access to University of Pittsburgh for a period of 1 year.
Number of Pages: 90
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Materials Science and Engineering
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: Inconel 718; Powder bed fusion; CALPHAD; Additive Manufacturing; Homogenization
Date Deposited: 18 Jun 2019 18:53
Last Modified: 18 Jun 2020 05:15


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