Influence of frequency and wave form on S-N fatigue of commercial austenitic stainless steels with different nickel contents in inert gas and in high pressure gaseous hydrogen

The main part of this investigation are S-N fatigue tests of austenitic stainless steels with different nickel contents (12.6-13.7 wt%) in high pressure gaseous helium and hydrogen at -50 degrees C to characterize the influence of hydrogen on the S-N curve. For the steel with 12.6 wt% Ni the low cycle fatigue life in hydrogen was about one order of magnitude lower compared to helium. The slopes of the two curves were comparable. The influence of hydrogen decreased with increasing nickel content, which is consistent with tensile test results. The S-N results in He were significantly influenced by the test frequency. Number of cycles to failure decreased with decreasing frequency until saturation at around 0.1 Hz. Hydrogen effects were predominant down to a frequency of about 1 Hz. Below 1 Hz, the decrease in numbers of cycles to failure was dominated by the frequency effect and not by the hydrogen effect. An increased effect of hydrogen for a trapezoid wave form compared to a triangle wave form could not be identified. (C) 2016 Elsevier Ltd. All rights reserved.