Temperature dependency of hydrogen embrittlement resistance of austenitic Fe–24Mn–3Cr-0.5Cu-0.47C steel

Abstract

Currently, austenitic stainless steel has been used as a tank material for liquid hydrogen storage. However, in this study, the resistance to hydrogen embrittlement (HE) of austenitic Fe–24Mn–3Cr-0.5Cu-0.47C steel was investigated at a wide temperature range from 300 K to 20 K through slow strain rate tensile tests, aiming to explore the possibility of Fe-high Mn steel as an alternative material. To date, there are few papers on the HE resistance of austenitic high Mn steel, especially at cryogenic temperatures. The HE resistance of the high Mn steel was compared to that of austenitic 304 stainless steel (STS 304). The HE resistance of the high Mn steel was continuously enhanced with decreasing tensile temperature from 300 K to 77 K, despite the occurrence of mechanical twinning due to the significant reduction in H diffusion. However, the HE resistance slightly decreased again at 20 K, primarily due to cracking induced by dislocations with an edge component. Although both the high Mn steel and STS 304 had similar resistance to HE in the temperature range of 123 K–20 K, the high Mn steel demonstrated superior resistance to HE at the temperature range of 123 K–300 K. This indicates that the strain-induced α′-martensitic transformation occurring in STS 304 during tensile deformation in that temperature range is more detrimental to the HE resistance compared to the mechanical twinning occurring in the high Mn steel.