Effects of Hydrogen Gas Environment on the Fatigue Strength at 107 cycles in the Plain Specimens of Type 316L Stainless Steel (A Report Focusing on the Behavior of Micro Fatigue Crack)

In order to investigate the hydrogen effect on the fatigue strength at 107 cycles of type 316L stainless steel, the rotating bending fatigue tests in atmospheric air and the plane bending fatigue tests in 1 MPa dry hydrogen gas and in air were carried out. The observed fatigue behavior showed that the fatigue strength at 107 cycles in both environments is determined by the non-propagation of fatigue crack of the order of the grain size. And, the strength at 107 cycles in hydrogen is slightly higher than that in air. In the region of long fatigue life, the fatigue life in hydrogen is longer than that in air, which is mainly caused by the longer crack initiation life in hydrogen. The crack propagation life in hydrogen is shorter than that in air, but has only a small ratio to the fatigue life in this region.