Page 33 - MSAM-3-1

Materials Science in

Additive Manufacturing

ORIGINAL RESEARCH ARTICLE
Effects of carbon content on precipitate

evolution and crack susceptibility in additively
manufactured IN738LC

Zhongji Sun *, Verner Soh , Coryl Lee , Delvin Wuu , Desmond Lau , Siyuan
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Wei , Chee Koon Ng , Swee Leong Sing , Dennis Tan , and Pei Wang *
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1 Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and
Research (A*STAR), Singapore, Republic of Singapore
2 Department of Mechanical Engineering, National University of Singapore, Singapore, Republic of
Singapore
3 Engineering Cluster, Singapore Institute of Technology, Singapore, Republic of Singapore
Abstract
Hot cracking is a major bottleneck preventing the additive manufacturing
community from adopting precipitation-strengthened nickel-base superalloys,
such as the IN738LC. Prior literature demonstrates the beneficial outcome of
increasing the carbon content within IN738LC to alleviate its hot cracking problem.
However, the effect of carbon content on the gamma prime precipitation and grain
recrystallization was not fully addressed. Here, we fabricated five sample sets of
*Corresponding authors: Zhongji IN738LC with different carbon contents and subjected these samples to two separate
Sun heat treatment processes. The precipitate and grain evolution were monitored under
(sun_zhongji@imre.a-star.edu.sg) the backscattered electron imaging and electron backscattered diffraction studies.
Pei Wang
(wangp@imre.a-star.edu.sg) While the carbon addition could assist in addressing the hot cracking problem,
horizontal delamination cracks were detected during the fabrication of large samples
Citation: Sun Z, Soh V, Lee C, when the overall carbon content was above 0.4 wt.%, highlighting the need for care
et al. Effects of carbon content
on precipitate evolution and when introducing carbon for the purpose of resolving hot cracking.
crack susceptibility in additively
manufactured IN738LC. Mater Sci
Add Manuf. 2024;3(1):2264. Keywords: Additive manufacturing; Cracking; Nickel-base superalloy; Carbon
doi: 10.36922/msam.2264
Received: November 16, 2023
Accepted: January 8, 2024 1. Introduction
Published Online: February 19, Precipitation-strengthened nickel-base superalloy IN738LC was originally designed
2024 as an investment casting alloy . It contains a high-volume fraction (about 45 %) of the
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Copyright: © 2024 Author(s). This coherent L1 Ni (Al, Ti) gamma prime (γ’) precipitates, which provides the material
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is an Open-Access article distributed with excellent high-temperature (up to 980°C) resistance to hot corrosion and desired
under the terms of the Creative
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Commons Attribution License, mechanical properties, enabling the alloy to serve as critical components within the
permitting distribution, and hot sections of land-based and aero gas turbines. The envisioned benefits of one-step
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reproduction in any medium,
provided the original work is properly near-net-shape production of this material through additive manufacturing (AM) have
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cited. driven many research efforts for the past half-decade. If successful, the AM approach
Publisher’s Note: AccScience could save on raw material feedstock and eliminate the need for post-machining,
Publishing remains neutral with which is a considerable cost for such an expensive and difficult-to-machine hard alloy.
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regard to jurisdictional claims in However, under AM’s rapid solidification conditions, for example, laser powder bed
published maps and institutional
affiliations. fusion (LPBF), IN738LC is prone to hot cracking. 11,12
Volume 3 Issue 1 (2024) 1 https://doi.org/10.36922/msam.2264