Low cycle fatigue and creep-fatigue interaction behaviour of 316L(N) stainless steel and its welds

High temperature low cycle fatigue (LCF) is influenced by various time dependent processes such as creep, oxidation, phase transformations and dynamic strain ageing (DSA) depending on test conditions of strain rate and temperature. In this paper the detrimental effects of DSA and oxidation in high temperature LCF are discussed with reference to extensive studies on 316L(N) stainless steel. DSA has been found to enhance the stress response and reduce ductility. It localizes fatigue deformation, enhances fatigue cracking and reduces fatigue life. High temperature oxidation accelerates transgranular and intergranular fatigue cracking during long hold time tests in austenitic stainless steel. In welds, microstructural features such as presence of coarse grains and formation of brittle phases due to transformation of delta ferrite during testing influence crack initiation, propagation and fatigue life.