Low Cycle Fatigue of Nitrogen Alloyed Martensitic Stainless Steels

Abstract

This study deals with the cyclic plasticity of high nitrogen martensitic steels obtained by the PESR process. In addition to the effect of nitrogen, it is shown that silicon also influences the fatigue properties. High cyclic stress values can be obtained in nitrogen plus silicon rich steel which does not exhibit a good fatigue resistance. In such alloy, the plasticity is strongly dependent not only on the precipate state but also on the interaction of dislocations with silicon atoms inducing an earlier fracture in lath martensite.The combined influence of non metallic alloying elements, C, N, Si on crack initiation is discussed. It is pointed out that soft phase like “ferrite” in conventional 12%Cr martensitic steel could be a way to combine both high mechanical properties and good cyclic plasticity.