Instrumented micro/macroindentation of porosity defects in laser powder bed fusion 316L stainless steel

Published

June 5, 2025

Author(s)

Jordan Weaver, Houshang Yin, Jesse Redford, Xiaoyuan Lou

Abstract

Porosity defects and their effect on mechanical properties remain a concern in metals-based laser powder bed fusion, even for optimized process parameters. Instrumented micro/macroindentation with Berkovich and spherical tips to forces of 50 N and 150 N, respectively, were used to characterize three levels of porosity (fully dense, 1%, and 4%) created by decreasing and increasing the hatch spacing and two levels of heat treatments (stress-relieved and solution annealed). The spherical indentation data were converted to effective stress–strain curves along with an estimated modulus and yield stress. The Berkovich data were analyzed using the Oliver-Pharr method for modulus and hardness, and the hardness was used to estimate yield stress. The indentation results were compared against tensile results for the loading axis along the build direction (Z) and perpendicular to the build direction (X/Y). The modulus results largely agree for indentation and tensile tests. The average yield stress estimated from these indentation measurements captures the difference in heat treatment but does not capture subtle changes in porosity and test direction compared to tensile yield stress measurements. However, the indentation results show a considerable increase in scatter from test to test with the presence of porosity due to varying amount of porosity within the interaction volume under the indenter.

Citation

Journal of Materials Science

Pub Type

Journals

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Keywords

lack-of-fusion, keyholing, yield stress, spherical indentation, stress-strain curves

Citation

Weaver, J. , Yin, H. , Redford, J. and Lou, X. (2025), Instrumented micro/macroindentation of porosity defects in laser powder bed fusion 316L stainless steel, Journal of Materials Science, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=958585 (Accessed June 8, 2025)