Internal Reversible Hydrogen Embrittlement of Austenitic Stainless Steels Based on Type 316 at Low Temperatures

The internal reversible hydrogen embrittlement (IRHE) of austenitic Fe(10–20)Ni17Cr2Mo alloys based on type 316 stainless steels hydrogen-charged to around 40 mass ppm was investigated by performing tensile tests using the slow strain rate technique at temperatures from 80 to 300 K. The susceptibility to IRHE depended on the Ni content. IRHE occurred below a Ni content of 15% (Ni equivalent of 29%), increased with decreasing temperature, reached a maximum at 200 K and decreased with further decreasing temperature. Hydrogen-induced fracture due to IRHE occurred in brittle transgranular mode associated with the strain-induced α' martensite structure at temperatures from 200 to 300 K and occurred simultaneously with fracture along the prior annealed-twin boundary at 200 and 250 K, then changed to dimple rupture mode due to hydrogen localization at 150 K. IRHE was controlled by the amount of strain-induced α' martensite above 200 K, whereas it was controlled by hydrogen diffusion below 200 K.