Mechanical properties of SS310 and IN625 following high-temperature hydrogen exposure

This paper seeks to address knowledge gaps regarding the stability of stainless steel and Inconel alloys to continuous high-temperature H 2 exposure. Stainless steel 310 (SS310) and Inconel 625 (IN625) were continuously exposed to hydrogen at 450 °C and 900 °C for up to 33 days. Materials properties were periodically examined through tensile, Charpy impact, and three-point bend tests; microstructure was examined by electron microscopy and X-ray diffraction. At 450 °C, both materials exhibit resilience to hydrogen ingress, with tensile, impact, and bend tests showing only modest changes in strength and ductility. At 900 °C, both alloys undergo pronounced degradation that bring sharp losses in toughness, intergranular fracture features, and evolving lattice parameters. These responses are compared with previously presented mechanisms of high-temperature hydrogen degradation.