International Hydrogen Conference (IHC 2012): Hydrogen-Materials Interactions
39 Fatigue Crack Initiation in Hydrogen-Precharged Austenitic Stainless Steel
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- Reference Manager
Hydrogen-assisted fatigue is a significant concern in hydrogen fueling infrastructure. Generally accepted testing procedures to evaluate the initiation of fatigue cracks in structural materials have not been established, particularly in hydrogen environments. Additionally, there is need to develop methods that accelerate testing in materials that may experience on the order of tens of thousands of cycles over many years. This task may be especially challenging in materials where the kinetics of hydrogen transport are very slow, such as austenitic stainless steels. In this study, hydrogen precharging is used to saturate a stable austenitic stainless steel with hydrogen prior to axial fatigue life testing with the aim of circumventing the kinetics of surface interactions in gaseous environments. Constant load amplitude in tension-tension is used to simulate the stress cycle that is experienced by pressure components. Circumferentially notched specimens are used to limit the applied stress in the specimens to values less than the yield strength of the material. Additionally, fatigue crack initiation was explored using a direct current potential difference (DCPD) method. For the range of explored parameters, crack initiation is found to account for 20 to 75% of the fatigue life, depending on the applied stress. Moreover, both the number of cycles to initiation and the number of cycles to failure are not affected by high concentration of internal hydrogen for austenitic stainless steel of the type 21Cr-6Ni-9Mn.