In-situ SEM and EBSD study on fretting fatigue crack initiation of a directionally solidified Ni-based superalloy

Abstract

Fretting fatigue is an important cause of the failure of the turbine blade-disc dovetail joint in aero-engines. In this work in-situ scanning electron microscope (SEM) fretting fatigue experiments using dovetail shape specimens were conducted. The fretting fatigue damage process of Ni-based directionally solidified superalloys including slip trace evolution and crack initiation was captured. The misorientation and geometrically necessary dislocation (GND) density induced by fretting fatigue were quantified by electron back-scattered diffraction (EBSD). The significant correlation between crack path, slip trace, grain boundary microstructure and GND density was revealed. The EBSD analysis achieved good agreement with the in-situ SEM observation.