Study on gradient structure and interface mechanical properties of n–8YSZ/AlCoCrFeNi high–entropy coatings

In this study, gradient and double-layer coatings were prepared by atmospheric plasma spraying (APS) with nano ZrO2–8%Y2O3(n–8YSZ)/AlCoCrFeNi high–entropy powder. The microhardness of the gradient coating changed in a manner consistent with the microstructure, and the average bond strength of the gradient coating was 2.50 times higher than that of the double-layer coating, indicating that the gradient structure of the coating can improve the sharp interface of the coating, and play a significant role in dispersion toughening to improve the bond strength of the coating. After 450 thermal cycles, the double-layer coating exhibited transverse propagation cracks accompanying coating spalling. In contrast, vertical cracks occurred inside the gradient coating, effectively increasing the coating strain tolerance and improving the coating life. Simultaneously, internal oxidation and cracks appeared in the substrate during cycles, the cracks were more obvious, and bridging occurred in the substrate of the double-layer coating, the substrate under the protection of the gradient coating produced microcracks that were discontinuous, indicating that the design of the gradient structure of the coating can effectively release the internal stress and improve the thermal shock resistance of the coating.