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

概要

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The internal reversible hydrogen embrittlement (IRHE) of austenitic Fe(10-20)Ni17Cr2Mo alloys based on type 316 stainless steel hydrogen-charged as 40 mass ppm was investigated by tensile tests using the slow strain rate technique from 80 to 300 K. 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. The susceptibility to IRHE depended on Ni content. Hydrogen-induced fracture of IRHE occurred in brittle transgranular mode associated with the strain-induced α' martensite structure from 200 to 300 K and mixed with twin boundary fracture at 200 and 250 K, and changed to dimple rupture mode due to hydrogen segregation at 150 K. IRHE was controlled by the amount of strain-induced α' martensite above 200 K, whereas it was controlled by the hydrogen diffusion below 200 K.