The internal reversible hydrogen embrittlement (IRHE) of the thermally hydrogen-charged iron-based superalloy of SUH660 and austenitic stainless steels of SUS 304, 316, 316L, 316LN and 310S was investigated in the temperature range from 300K to 80 K. Hydrogen showed a marked effect on the tensile properties of SUH660 and SUS 304, a minimal effect on those of SUS316 and SUS316LN, and no effect on those of SUS 310S and 316L at room temperature. Although the IRHE of SUH660 decreased with decreasing temperature, those of SUS304, 316 and 316LN increased with decreasing temperature, reached a maximum at around 200 K, and decreased rapidly with decreasing temperature down to 80 K. It was observed that hydrogen caused transgranular fracture along the slip plane in the iron-based superalloy and brittle transgranular fracture along the strain-induced martensite lath in the austenitic stainless steels, respectively. It was suggested that IRHE of the SUH660 depended on the diffusion of hydrogen, and that IRHE of the austenitic stainless steels from 300 K to the maximum IRHE temperature depended on the transformation of strain-induced martensite and the behavior below the maximum IRHE temperature depended on the diffusion of hydrogen.
