Effects of thickness debit and stress concentration on superalloy DZ125 subjected to cyclic loading

Abstract

In this paper, the thickness debit and stress concentration effects of a nickel-based directionally solidified superalloy were investigated through strain-controlled low cycle fatigue (LCF) and creep–fatigue interaction (CFI) experiments. Compared to the fatigue lives of solid specimens provided in the existing literature, the results of this paper indicate that when the wall thickness of the specimen is reduced from 5 to 1.125 mm, the fatigue life with different strain amplitudes decreases by about 45%. When film-cooling holes (FCHs) are introduced into the hollow specimens, the fatigue life is further reduced by about 25%. Based on the observation of the scanning electron microscope (SEM), the formation mechanisms of the thickness debit and stress concentration effects under LCF and CFI loads were revealed. Subsequently, two parameters, the “wall-thickness coefficient” and “hole coefficient,” were proposed to establish a new fatigue life prediction method.