In-situ fatigue behavior study of a nickel-based single-crystal superalloy with different orientations

Abstract

This work studied the relationship between the fatigue behavior and microstructural evolution of a second-generation nickel-based single-crystal superalloy with [001], [102], and [314] orientations at room temperature. Strain-controlled low-cycle fatigue experiments were executed using an in-situ Scanning electron microscope (SEM) fatigue test system. Digital image correlation (DIC) mapping combined with SEM images were used to identify strain concentration and predict areas of crack initiation. Results showed that the deformation of specimens with different orientations was dominated by planar slip and followed Schmid law. Cross-slips were observed in the specimen with the [001] oriented orientation, while a single slip was observed for the other two orientations. Fatigue crack propagation was dominated by one slip system in the [001] and [314] oriented specimens. While in the [102] oriented specimen, it was alternately dominated by two slip systems. The fatigue life of Nickel-based single-crystal superalloys (NBSCs) had a high orientation dependence, and was related to the elastic modulus and crack propagation path. The cyclic softening that occurred during fatigue was caused by dislocation motion.