Rotating bending fatigue property of SCM435 during electrochemical hydrogen charging

The method of rotating bending fatigue test under an electrochemical hydrogen-charging was established, by which the fatigue tests were carried out for a JIS-SCM435 to study the effect of hydrogen on fatigue strength. The fatigue life of the specimen was degraded by hydrogen -charging in relatively low fatigue life regime, where the slope of S-N curve for the hydrogen-charged specimens was equivalent to that for no-charged specimens. The fatigue strength on 50% failure probability at 107 cycles under the hydrogen-charging was slightly lower than that under the hydrogen-free condition. On the surface of the non-charged specimen that was run-out at 107 cycles, a number of cracks up to ≈100 μm in length was observed. By contrast, in the hydrogen-charged specimen, no crack was observed after the fatigue testing. These results suggested that the hydrogen-charging had a negative infiuence on the fatigue limit as well as fatigue life of the alloy used in this study.