Fatigue behaviors of high nitrogen stainless steels with different deformation modes

In this work, high-cycle fatigue property of high nitrogen steels which have different deformation modes was explored. The samples, Fe-18Cr-10Mn-0.4N (0.4N) and Fe-18Cr-10Mn-0.6N (0.6N), were fabricated under different nitrogen partial pressures in order to obtain the different deformation modes by controlling stacking fault energy: Deformation-Induced Martensite Transformation (DIMT) in 0.4N and deformation twins in 0.6N. Owing to solid solution strengthening of nitrogen, the fatigue limit of 0.6N is higher than that of 0.4N. However, a ratio of the fatigue limit to the yield strength of 0.6N is lower than that of 0.4N. This result is ascribed to the different influence of the deformation modes on fatigue damages. The DIMT formed in 0.4N could restrict the path of moving dislocations, and thus the fatigue property was relatively improved with the decrease of the fatigue damages by the DIMT. The deformation twins, on the other hand, were not clearly activated during fatigue of 0.6N, and therefore did not affect the fatigue damages.