Influence of high pressure gaseous hydrogen on S-N fatigue in two austenitic stainless steels

Load controlled S-N fatigue tests (R = 0.1, 1 Hz, notched cylindrical specimen with k(t) = 3.4) in the low cycle fatigue regime in hydrogen and helium gas atmospheres (10 MPa, room temperature and -50 degrees C) were performed on two austenitic stainless steels (SS) with nickel contents of 11.4 and 12.7 wt.%, respectively. At room temperature the 11.4Ni SS showed a considerable reduction in total fatigue life at high stress amplitudes which mitigates with decreasing stress amplitudes. Striation analysis showed that the growth of stage I and stage II cracks is accelerated in hydrogen atmosphere compared to helium atmosphere. For the 12.7Ni SS no significant difference between the fatigue lives in hydrogen and helium was found verifying the positive effect of higher nickel concentrations also in fatigue life tests. At -50 degrees C, both steels showed a reduction in total fatigue life. Comparing the loss of fatigue strength to the loss of tensile reduction of area revealed a much higher severity of hydrogen on the loss of tensile RA. (C) 2013 Elsevier Ltd. All rights reserved.