Influence of low temperature prestrain on hydrogen gas embrittlement of metastable austenitic stainless steels

The effect of the prestrain at 80 K on hydrogen gas embrittlement (HGE) of Fe–Ni(10–16)–Cr17–Mo2 alloys, based on type 316 stainless steel, was investigated in 1 MPa hydrogen and helium at 200 K. The HGE susceptibility of the alloy decreases with increasing prestrain and nickel equivalent, and no HGE is observed above the prestrain of 30% and the nickel equivalent of 27.2%. The fracture mode strongly depends on the prestrain and changes from the brittle transgranular fracture to the ductile dimple rupture with increasing prestrain. Prior strain induced α′ martensite formed by the prestrain at 80 K does not show HGE, while dynamic strain induced α′ martensite formed during the deformation after the prestrain shows HGE at 200 K.