SSRT and fatigue crack growth properties of two types of high strength austenitic stainless steels in high pressure hydrogen gas

The susceptibility to hydrogen embrittlement of two types of high strength austenitic stainless steels containing a small amount nitrogen and niobium were investigated by conducting a series of slow strain rate tests (SSRT) and fatigue crack growth tests in hydrogen gas with a pressure of around 100 MPa. The JIS-SUS304 and JIS-SUS316L austenitic stainless steels were also tested for a comparative purpose. In JIS-SUS304, the tensile strength and reduction of area in hydrogen gas were much lower than those in air. In contrast, in JIS-SUS316L, the degradation of those tensile properties in hydrogen gas was not so significant. The high strength austenitic stainless steels also exhibited an excellent resistance both in tensile strength and ductility in hydrogen gas. In JIS-SUS304, the fatigue crack growth in hydrogen gas was 10 times as fast as that in air, while the factor of acceleration remained within 1.5 3 in JIS-SUS316L and the high strength austenitic stainless steels. It was presumed that, in those high strength austenitic stainless steels, a small amount of added elements, N and Nb, increased the strength level as well as the stability of austenitic phase, which thereby led to the excellent resistance against hydrogen embrittlement.