Phenomenological Modeling of the Effect of Oxidation on the Creep Response of Ni-Based Single-Crystal Superalloys

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 the amount of accumulated plastic strain and stress triaxiality. The effect of oxidation on the mechanical behavior and damage is considered at the flow stress level by modifying the amplitude of the kinematic hardening. The oxidation-altered kinematic hardening is able to predict the effect of oxidizing environments on the mechanical behavior, specifically the plastic strain rate in the secondary creep stage, and lifetime. In addition, the oxidation model has also been tested in 3D by performing a finite-element simulation on a notched specimen subjected to a creep load. It revealed that the model is able to predict surface roughness and oxide thickness distributions in 3D and for multiaxial stresses.