Fatigue crack growth of a metastable austenitic stainless steel

•In metastable austenitic stainless steel (MASS) for a given ΔK and load ratio, the FCGR is independent of the mean stress.•For MASS, the crack closure cannot explain the effects of the load ratio in the FCGR.•For MASS, the Kujawski’s parameter can successfully correlate the load ratio effects.•The zone of martensitic transformation is proportional to the cyclic plastic zone.•The exceptional FCGR of MASS can be partially explained by the residual stresses.

The fatigue crack growth behavior of an austenitic metastable stainless steel AISI 301LN in the Paris region is investigated in this work. The fatigue crack growth rate curves are evaluated in terms of different parameters such as the range of stress intensity factor ΔK, the effective stress intensity factor ΔKeff, and the two driving force parameter proposed by Kujawski K∗.The finite element method is used to calculate the stress intensity factor of the specimens used in this investigation. The new stress intensity factor solution has been proved to be an alternative to explain contradictory results found in the literature.Fatigue crack propagation tests have been carried out on thin sheets with two different microstructural conditions and different load ratios. The influence of microstructural and mechanical variables has been analyzed using different mechanisms proposed in the literature. The influence of the compressive residual stress induced by the martensitic transformation is determined by using a model based on the proposal of McMeeking et al. The analyses demonstrate the necessity of including Kmax as a true driving force for the fatigue crack growth. A combined parameter is proposed to explain the effects of different variables on the fatigue crack growth rate curves. It is found that along with residual stresses, the microcracks and microvoids are other factor affecting the fatigue crack growth rate in the steel studied.