Evolution rules of thermal cycling residual stress in ceramic sealing coatings with “brick-mud” structure

Residual stress is the direct driving force for the delamination and failure of ceramic coatings during thermal cycling. The evolution rules of thermal cycling residual stress in yttrium oxide partially stabilized zirconia (YSZ) ceramic sealing coatings with conventional and “brick-mud” structures were researched in this paper. The results showed that, after experiencing different thermal cycles, the coordinate distributions of the residual stress specimens with conventional and “brick-mud” structure coatings both followed parabolic function laws. The R-square values of all fitted curves exceeded 0.9, and the RMSE values were close to 0. The parabolic models obtained in this study had good curve-fitting degrees to the original coordinates of residual stress test specimens, and the calculation method of curvature radius based on the parabolic model had high accuracy. As the number of thermal cycles increased, the conventional structural coatings mainly included the initial stage, the rapid growth stage of residual stress and the failure stage. The residual stress showed a piecewise evolution law composed of three parabolic functions. While the “brick-mud” structured coatings mainly included the initial and stable stages of thermal cycling, and their corresponding residual stress showed a two-stage segmented function evolution law composed of a parabolic function and a periodic second-order Fourier function. In addition, the above Fourier function had an extremely small amplitude value, which demonstrated that the residual stress of the “brick-mud” structured specimens exhibited a periodic and low amplitude evolution rule during the stable stage of thermal cycling. This research establishes a curvature radius calculation method based on mathematical models and elucidates the thermal cycling residual stress evolution rules of “brick-mud” structured coatings.