Hydrogen diffusivity and tensile-ductility loss of solution-treated austenitic stainless steels with external and internal hydrogen

The effects of external and internal hydrogen on the slow-strain-rate tensile (SSRT) properties at room temperature were studied for ten types of solution-treated austenitic stainless steels containing a small amount of additive elements. The hydrogen diffusivity and solubility of the steels were measured with high-pressure hydrogen gas. The remarkable tensile-ductility loss observed in the SSRT tests was attributed to hydrogen induced successive crack growth (HISCG) and was successfully quantified according to the nickel-equivalent content (Ni-eq), which represents the stability of the austenitic phase. The relative reduction in area (RRA) of the steels with a larger Ni-eq was influenced by the hydrogen distribution, whereas that of the steels with a smaller Ni-eq was not. This unique trend was interpreted with regard to the hydrogen distribution and fracture morphology (HISCG or microvoid coalescence). (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.