Recently, a simple screening technique based on the quantitative evaluation of the hydrogen embrittlement (HE) sensitivity of the metallic materials using an in-situ small-punch (SP) test method was developed by the author group. The in-situ SP test can be easily carried out even under a high-pressure hydrogen gas environment. It makes possible to investigate the HE behaviors of metallic materials quantitatively adopting as a characterizing performance factor of the relative reduction of thickness (RRT) measured at the fractured parts of specimen after SP tests. In this paper, the application of the newly established in-situ SP test method for the hydrogen compatibility screening of austenitic stainless steels was performed at room and low temperatures. The influence of punch velocity on RRT of the HE sensitivity was examined for various austenitic stainless steels. Their HE sensitivities were evaluated quantitatively using RRT and checked by comparing to a factor, the relative reduction of area (RRA) obtained by SSRT tests.

An in-situ small punch (SP) test method has recently been developed as a simple screening technique for evaluating the properties of metallic materials used in high-pressure hydrogen environments. With this method, the test conditions including temperature and gas pressure can easily be adjusted to those used in practice. In this study, specimens of STS316L steel and 18 wt% Mn steel were prepared at two different surface roughness, fabricated using wire-cutting and mechanical polishing. Their effects on hydrogen embrittlement (HE) were evaluated using in-situ SP testing at both room temperature and a lower temperature where HE was shown to occur under 10 MPa hydrogen. Both steels were evaluated using two variables obtained from in-situ SP testing, the SP energy, and the relative reduction of thickness (RRT), to quantitatively determine the effect of specimen surface roughness on HE susceptibility. Their fracture characteristics due to HE under 10 MPa hydrogen showed little difference with surface finish. Surface roughness had a negligible influence on these quantitative factors describing HE, indicating that it is not a dominant factor to be considered in in-situ SP testing when it is used to screen for HE compatibility in steels used in high-pressure hydrogen environments.

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A simple screening technique of hydrogen embrittlement (HE) of steels for hydrogen energy facilities using an in-situ small-punch (SP) test method under external hydrogen condition has been established. Using this method, we investigated the HE behaviors of API X70 steel welds under test conditions mimicking pipeline operating environments. The HE sensitivity at each region of the base metal, heat-affected zone, and weld metal of the steel weld was examined qualitatively and quantitatively and compared to one another. Under 8 MPa H2 gas, the welds showed pronounced HE: the HE behaviors induced were similar across all tested regions. This shows that the in-situ SP test is effective for screening HE susceptibility of pipeline steel welds in high-pressure hydrogen environments.