Thermomechanical fatigue properties and microstructural damage of nitrogen alloyed 316LN stainless steel

Abstract In-phase (IP) and out-of-phase (OP) thermomechanical fatigue (TMF) tests are carried out to investigate the cyclic deformation behavior, microstructural damage and cracking behavior of 316LN stainless steel. The result shows that dynamic strain aging (DSA) and oxidation are the two principal deformation and damage mechanisms. DSA occurs within the temperature range of 250 °C-450 °C, and the action intensity of which increases from 250 °C to 450 °C. Oxide layers preferentially form along surface persistent slip markings, which accelerates the microcrack nucleation and crack propagation, leading to an oxidation-assisted transgranular failure. The fatigue life under IP-TMF and OP-TMF loadings are approximately equal and longer than that under IF-450 °C loadings.