Surface oxidation behavior and anti-ablation mechanism of plasma sprayed ZrC-ZrSi2-Al2O3 composite coating under plasma torch ablation

A ZrC-ZrSi2-Al2O3 coating system was designed and prepared by atmospheric plasma spraying. Densely packed whisker microstructure and alumina-zirconia hypoeutectic were found in the as-prepared coating. The surface oxidation behavior of this composite coating under plasma torch ablation was fully revealed based on the characterizations from macroscopic to microscopic perspectives. After 20 s ablation, the major phases on the coating surface are t-ZrO2, Al2O3, SiO2, ZrSiO4, and ZrSi2. ZrC-ZrSi2 whiskers showed good integrity during the ablation process and finally, a dense Zr-Si-O layer was formed in the whisker area. Good coordination between alumina and zirconia is obtained by forming the solid solution and eutectic on the after-ablation coating surface. The as-prepared coating showed promising failure resistance under plasma torch ablation.