HfC-ZrC-SiC multiphase protective coating for SiC-coated C/C composites prepared by supersonic atmospheric plasma spraying

HfC-ZrC-SiC (HZS) multiphase coating was deposited on the surface of SiC-coated carbon/carbon composites by supersonic atmospheric plasma spraying. The morphology and microstructure of HZS coating were characterized by XRD and SEM. The as-prepared coating was composed of different carbides and oxides. The structure was dense and crack free. Each element distributed uniformly in the coating. Ablation resistance test was carried out by oxyacetylene torch. During ablation, the outer coating underwent a process of solid state sintering and formed a dense Hf-Zr-Si-O layer on the surface of coating gradually, which could prevent the oxygen diffusing inward. The inner coating was oxidized gradually with the oxygen permeation and the structure was loose. In addition, the newly formed HfSiO₄ and ZrSiO₄ were generated after cooling, which could play a pinning effect and prevent crack extension.