Investigations of elastic modulus and hardness of air plasma sprayed thermal barrier coatings by nanoindentation method

The parabolic evolutions of elastic modulus and hardness of air plasma sprayed thermal barrier coatings under thermal cycles were studied by nanoindentation method. The experimental data were analyzed by Weibull statistical method to minimize the measurement scatter. The results indicated that elastic modulus and hardness in the interface region of the coating display anisotropic distribution. They increase with thermal cycling and then gradually keep a constant after some thermal cycles. The values of elastic modulus and hardness in the cross-sectional coating are larger than that in the coating surface region. The reason was discussed with the aid of the scanning electronic microscope observations.