X-ray residual stress analysis of a ceramic thermal barrier coating undergoing thermal cycling

The residual stress of a ZrO_2-8%Y_2O_3 thermal barrier coating was determined as a function of thermal cycling. Samples were thermally cycled from 400°C to 1000°C in air. After a few cycles the samples exhibited a value of compressive residual stress consistent with that determined by considering the thermal expansion coefficients of the coating and substrate. Stress relief occurs in the ZrO_2-Y_2O_3 coating, increasing in both frequency and magnitude with increasing number of thermal cycles. This behavior is explained in terms of a model of failure of coatings in compression.