Hydrogen penetration properties into stainless steels with and without pre-strain exposed to high-pressure hydrogen environments and effects of hydrogen and martensite on fatigue crack growth behavior of SUS304, SUS316L and SUS310S were investigated. The hydrogen penetration behavior into the austenitic stainless steels was successfully expressed by Sieverts' and Fick's laws. In SUS304, the fatigue crack growth rates in the hydrogen-exposed specimen were approximately twice as high as those in the uncharged specimen, while in SUS316L, only slight acceleration in the crack growth rate due to hydrogen was observed only when the crack length was short. Although the hydrogen content and distribution from surface to subsurface in the fatigue specimen influenced the fatigue crack growth, the method of hydrogen charge was not substantial. In the hydrogen-exposed SUS304 specimen, slip bands were less and more discrete and the crack morphology was straighter and thinner. This suggests that hydrogen caused slip localization and accordingly affecting the fatigue crack growth behavior. The estimated hydrogen penetration depths into SUS304 indicate that the presence of strain-induced martensite increases hydrogen diffusivity in the steel. In a hydrogen-exposed stable austenitic stainless steel SUS310S, slip bands were discrete and a significant number of microcracks were generated along the slip bands. It can be concluded that the accelerations in fatigue crack growth rates in the hydrogen-charged austenitic stainless steels were essentially based on slip localization due to dissolved hydrogen, and that the strain-induced martensite in the austenitic stainless steels played a role in facilitation of slip localization with hydrogen.
