Phenomenological modeling of the effect of oxidation on the creep response of Ni-based single-crystal superalloys

Abstract

A new constitutive equation predicting the evolution of oxide thickness is proposed and implemented in a crystal plasticity framework with a hardening-based damage density function. The oxidation model depends on the initial surface roughness as well as on the amount of accumulated plastic strain and stress triaxiality. The description for the effect of oxidation on the mechanical behavior and damage is at the flow-stress level by modifying the amplitude of the kinematic hardening. The oxidation-altered kinematic hardening can predict the effect of oxidizing environments on mechanical behavior, specifically the plastic strain rate in the secondary creep stage, and lifetime. Finally, the oxidation model is verified to predict surface roughness and oxide thickness distributions by performing a finite-element simulation on a notched specimen subjected to creep and developing a complex multiaxial stress field.