Establishment of an in-situ small punch test method for characterizing hydrogen embrittlement behaviors under hydrogen gas environments and new influencing factor

Abstract

The hydrogen embrittlement (HE) behaviors of structural materials used to handle hydrogen must be tested at their use environments. In this study, an in-situ small punch (SP) test method was established to characterize HE behaviors of SA372 and STS304 steels under hydrogen gas environments at high pressures and low temperatures. In addition, a new influencing factor, relative reduction of thickness (RRT) was proposed to quantify the HE sensitivity of structural steels. Under 10 MPa H2 gas environment, load-displacement curves obtained and fractographic morphologies of the recovered specimens were analyzed to investigate the HE behaviors based on punch velocity and test temperature. When the HE sensitivity was evaluated by RRT, STS304 steel appeared to be vulnerable to HE as compared to SA372 steel across the tested temperature range. As a result, it was found that in-situ SP test and RRT can be used to quantify the HE sensitivity for structural materials screening regardless of test environments.