In order to investigate the hydrogen effect on crack initiation and growth behavior in an 18Cr-8Ni austenitic stainless steel, fatigue tests were carried out in pure hydrogen gas and in pure nitrogen gas at low pressure and in air. Following results are obtained. The crack initiation life in air is shorter than that in hydrogen gas and in nitrogen gas. The retardation of the crack initiation seems to be attributed to the absence of oxygen or water vapor in the hydrogen, gas. The crack growth rate in hydrogen gas accelerates compared with that in air. Hydrogen mainly affects slip behavior such that slip bands concentrate at a crack tip and result in the acceleration of growth rate. Non-propagating crack are observed in air, in hydrogen gas and in nitrogen gas. There is no significant difference in the stress level of non-propagating cracks, however there seems to be difference in mechanisms of non-propagating behavior.
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