Determination of Creep Behavior of Thermal Barrier Coatings Under Laser ImposedTemperature and Stress Gradients

摘要

In the present study, a laser sintering/creep technique has been established toquantitatively determine the creep behavior of thermal barrier coatings under steady state high heat flux/high thermal gradient conditions. An approach is proposed to separate the strong influence of stress relaxation, based on the deduced strain rate changes with respect to time and temperature during testing. For a plasma sprayed zirconia-8wt.% yttria ceramic coating, a large primary creep strain and a low creep activation energy were observed. The significant primary creep stage and low apparent creep activation energy for the coating are attributed to stress induced mechanical sliding, and temperature and stress enhanced cation diffusion through the splat and grain boundaries. Possible creep mechanisms for the ceramic coating are also discussed. The elastic modulus evolution, the stress response and the total accumulated creep strain variation across the ceramic coating under laser imposed temperature and stress conditions are simulated using a finite difference approach. The modeled creep response is consistent with experimental observations.