Dual role of hydrogen in fatigue life of 316L austenitic stainless steel

The presence of hydrogen can significantly alter the fatigue behavior of materials, posing a serious threat to the safe and reliable operation of components. In this study, an electrochemical in-situ hydrogen charging fatigue testing method was used to examine the effect of hydrogen on the fatigue strength and lifetime of 316L austenitic stainless steel. The impact of hydrogen on fatigue fracture behavior was analyzed using scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). The results indicated that, compared to specimens tested in air, in-situ charging increases the fatigue lifetime at higher stress amplitudes but significantly reduces it at lower stress amplitudes. Regardless of the testing environment, the crack initiation lifetime constitutes the majority of the total fatigue lifetime. Notably, at higher stress amplitudes, hydrogen greatly extends the fatigue crack initiation lifetime, whereas, at lower stress amplitudes, it has the opposite effect. This is attributed to the influence of hydrogen on dislocation motion patterns, which lowers the critical stress for dislocation plane slip. Hydrogen plays a dual role in the fatigue behavior of 316L steel.