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Materials Science in Additive Manufacturing Carbon addition in IN738LC

this approach are investigated in detail, namely, the size Investigation: Coryl Lee
and distribution of γ’, the ease of recrystallization, and the Methodology: Delvin Wuu, Desmond Lau
presence of large delamination cracks. Visualization: Siyuan Wei, Chee Koon Ng
Writing – original draft: Zhongji Sun
(i). The effect of carbon addition on the γ’ precipitation is
limited when the addition amount is about 0.1 wt.%. Writing – review & editing: Zhongji Sun, Swee Leong Sing,
Under the conventional two-step HT, the γ’ has a typical Dennis Tan, Pei Wang
bimodal distribution, with the primary γ’ being around Ethics approval and consent to participate
200 to 400 nm and the secondary γ’ about 100 nm.
However, with the addition of 0.3 wt.% carbon, the γ’ Not applicable.
precipitation is severely restricted. Instead, MC carbide
becomes the dominant precipitate, which increases the Consent for publication
material’s room-temperature hardness and strength. Not applicable.
(ii). The carbon content is found to be very sensitive toward
grain recrystallization. Even with an addition of 0.1 wt.% Availability of data
carbon, the recrystallization is limited to large columnar Data are available from the corresponding author on
grains. Only the original IN738LC composition could reasonable request.
be fully recrystallized and form equiaxed grains with
annealing twins. With additional carbon, they could References
facilitate early grain nucleation during recrystallization. 1. Guo C, Yu Z, Hu X, et al. Y2O3 nanoparticles decorated
However, large carbides with a size of about 1.8 μm IN738LC superalloy manufactured by laser powder bed
will eventually form and pin the high-angle grain fusion: Cracking inhibition, microstructures and mechanical
boundaries and restrict their migration. properties. Compos Part B Eng. 2022;230:109555.
(iii). Horizontal delamination cracks occurred during the doi: 10.1016/j.compositesb.2021.109555
production of large specimens with the dimension
of 45 × 10 × 10 mm . No crack was observed for 2. Xu J, Ding Y, Gao Y, et al. Improving high-temperature
3
smaller samples (cross-sectional area of 10 × 10 mm ) mechanical properties of laser powder bed-fused Inconel
2
fabricated using the same LPBF production 738 alloy by hot isostatic pressing: Tailoring precipitates and
healing defects. Mater Sci Eng A. 2023;862:144285.
parameters. Such cracks are frequently observed for
alloys containing a high density of hard precipitates, doi: 10.1016/j.msea.2022.144285
and their formation is often attributed to the inherent 3. Zhang L, Li Y, Zhang Q, Zhang S. Microstructure evolution,
high residual stresses. phase transformation and mechanical properties of IN738
superalloy fabricated by selective laser melting under
Acknowledgments different heat treatments. Mater Sci Eng A. 2022;844:142947.
None. doi: 10.1016/j.msea.2022.142947

Funding 4. Sotov AV, Agapovichev AV, Smelov VG, et al. Investigation
of the IN-738 superalloy microstructure and mechanical
Z. Sun acknowledges financial support from the Career properties for the manufacturing of gas turbine engine
Development Fund (grant reference no.: C222812017), nozzle guide vane by selective laser melting. Int J Adv Manuf
Young Individual Research Grant (Grant reference no.: Technol. 2020;107(5-6):2525-2535.
M22K3c0096); and P. Wang acknowledges the financial doi: 10.1007/s00170-020-05197-x
support from the Individual Research Grant (grant 5. Rickenbacher L, Etter T, Hövel S, Wegener K. High
reference no.: A20E7c0109) from the Agency for Science, temperature material properties of IN738LC processed by
Technology and Research of Singapore. selective laser melting (SLM) technology. Rapid Prototyp J.
2013;19(4):282-290.
Conflict of interest
doi: 10.1108/13552541311323281
No potential competing interests.
6. Vilanova M, Garciandia F, Sainz S, Jorge-Badiola D,
Author contributions Guraya T, San Sebastian M. The limit of hot isostatic pressing
for healing cracks present in an additively manufactured
Conceptualization: Zhongji Sun nickel superalloy. J Mater Process Technol. 2022;300:117398.
Formal analysis: Verner Soh doi: 10.1016/j.jmatprotec.2021.117398

Volume 3 Issue 1 (2024) 11 https://doi.org/10.36922/msam.2264