Numerical analysis for characterizing hydrogen embrittlement behaviors induced in STS316L stainless steel using an in-situ small-punch test

Abstract

In-situ small-punch (SP) tests have recently been used to characterize the susceptibility to hydrogen embrittlement (HE) of various steels. Most techniques for HE evaluation have been based on the use of initially hydrogen pre-charged specimens. However, in internal hydrogen conditions, consistent results are not obtained for the embrittlement and fracture behavior in comparison to those under external hydrogen conditions. In this study, an in-situ SP test was used to evaluate the HE susceptibility in 316L austenitic stainless steel. The test was carried out in 10-MPa gas environments at room temperature (RT) and below with different punch velocities. The results showed that at 10-MPa H2 gas, STS316L steel exhibited good resistance to HE at RT and −10 °C. However, the susceptibility to HE depended on the test temperature and punch velocity. A numerical simulation of the SP test was used to systematically compensate for the insufficient explanation of the crack formation that occurred during in-situ SP testing and to investigate the interaction of the punch velocity and the stress field in regard to the HE effect. The numerical analysis results support the experimental findings and provide a detailed explanation of factors such as the friction coefficient, strain rate, and stress state which lead to crack formation through their interaction in hydrogen-embrittled steel.