Effect of test temperature and strain rate on elevated temperature tensile tests of Inconel 718 prepared by selective laser melting

Tait D. McLouth; David B. Witkin; Julian R. Lohser; Scott D. Sitzman; Paul M. Adams; Glenn E. Bean; Jenn-Ming Yang; Rafael J. Zaldivar

doi:10.1117/12.2613475

4 March 2022 Effect of test temperature and strain rate on elevated temperature tensile tests of Inconel 718 prepared by selective laser melting

Tait D. McLouth, David B. Witkin, Julian R. Lohser, Scott D. Sitzman, Paul M. Adams, Glenn E. Bean, Jenn-Ming Yang, Rafael J. Zaldivar

Author Affiliations +

Proceedings Volume 11992, Laser 3D Manufacturing IX; 1199205 (2022) https://doi.org/10.1117/12.2613475
Event: SPIE LASE, 2022, San Francisco, California, United States

Abstract

This study analyzes the elevated temperature tensile results of SLM IN718 as a function of strain rate and test temperature in order to better understand the temporal and thermal aspects of environmental sensitivity. Fully heat-treated SLM samples are directly compared to wrought material and corresponding industry standards in order to provide a valuable perspective on the current state of SLM capabilities. It is found that SLM material tested across all conditions have inferior strength and ductility compared to wrought material of the same heat treatment. Strength variation is attributed to different sizes of the primary strengthening phase, γ’’, while ductility variation is caused by environmental sensitivity. SLM samples show evidence of brittle intergranular fracture, crack growth, and oxidized NbC particles on the fracture surface. These features are intensified with decreasing strain rate and increasing temperature. EBSD-generated misorientation maps and strain rate sensitivity calculations demonstrate that the mechanism of plastic deformation is similar between the two processing conditions but wrought material has a greater overall damage tolerance. Premature failure attributed to intergranular crack growth leads to poor ductility in SLM material. Faster strain rates and lower temperatures are shown to improve the ductility in SLM IN718 but despite this recovery it remains susceptible to environmental attack even in the extreme cases of the current study. Sources of environmental sensitivity and the degree to which they affect elevated temperature mechanical properties are discussed.

Conference Presentation

Citation Download Citation

Tait D. McLouth, David B. Witkin, Julian R. Lohser, Scott D. Sitzman, Paul M. Adams, Glenn E. Bean, Jenn-Ming Yang, and Rafael J. Zaldivar "Effect of test temperature and strain rate on elevated temperature tensile tests of Inconel 718 prepared by selective laser melting", Proc. SPIE 11992, Laser 3D Manufacturing IX, 1199205 (4 March 2022); https://doi.org/10.1117/12.2613475

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