OS12F008 Assessment of Fatigue Crack Propagation Behavior near Crystallographic Orientation Boundaries in Polycrystalline Ni-base Superalloys

Abstract

Fatigue crack propagation of Ni-based superalloys which possessed large grains comparable to the specimen thickness was investigated at room temperature. Special focus was put on the interactions with grain boundaries. For the purpose, at first the effect of crystallographic orientation on the crack propagation rate was studied, using the single crystal superalloy specimens made of CMSX-4 with different primary and secondary orientations. Some discussions were also made on what mechanics and mechanisms controlled the behavior, on the basis of anisotropic fracture mechanics. Based on these findings, some significant interactions between the crack and grain boundaries were discussed specifying the IN939 polycrystalline superalloy specimen.