The framework of hot corrosion fatigue life estimation of a PM superalloy using notch fatigue methodology combined with pit evolution

Abstract

This paper proposes a novel corrosion fatigue life estimation methodology considering the effect of hot corrosion and non-uniform stress field. The period of corrosion pit growing to the critical size was assessed by Faraday law. According to the cyclically plastic material constitutive response of smooth specimen, the finite element analysis was performed by regarding the critical corrosion pit as a micro semi-ellipsoidal notch. A novel definition about the effective strain was proposed considering the effect of non-uniform stress field in the high stress zone. The fatigue life from pit formation to final fracture was estimated by introducing the defined effective strain amplitude into Manson-Coffin-Basquin, Morrow, SWT and Walker models. Compared with the existing classical approaches, such as hot spot-based, continuum damage mechanics-based, strain energy-based models, the proposed approach provided significantly better corrosion fatigue life prediction. Finally, Walker model was suggested as the most suitable one after further discussion about the effect of mean stress.