In order to investigate the influence of hydrogen on the fatigue strength of Type 304 meta-stable austenitic stainless steel, specimens were cathodically charged with hydrogen. Hydrogen-charging led to a marked decrease in fatigue crack growth life. Crack growth paths and slip bands morphology were changed by the hydrogen-charging. To elucidate the mechanism of the degradation by hydrogen, the surfaces of both the uncharged and charged specimens were examined by the hydrogen microprint technique (HMT). In the uncharged specimen, no hydrogen emission from specimen surface was observed. On the other hand, in the hydrogen-charged specimen, a hydrogen emission was observed, especially in the vicinity of fatigue cracks. Hydrogen was mainly emitted from slip bands. These results suggest that the degradation of fatigue crack growth resistance in hydrogen-charged specimens was caused by the diffusion of hydrogen to slip bands, which accelerated the dislocation mobility and thereby facilitated the fatigue crack growth.
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