Ablation resistance under different heat fluxes of HfC-ZrC-SiC multiphase coating prepared by supersonic atmospheric plasma spraying for C/C composites

Abstract

To prevent the ablation of C/C composites, an HfC-ZrC-SiC multiphase coating was prepared by supersonic atmospheric plasma spraying. The morphology and microstructure of the coating were examined by X-ray diffraction and scanning electron microscopy, respectively. The as-prepared coating showed a compact structure with a few defects. The ablation resistance test of the coatings was carried out using an oxyacetylene torch under different heat fluxes. The samples ablated under different heat fluxes showed different ablation properties and ablation morphologies. During the ablation, the thickness and weight of the coating decreased with an increase in the heat flux from 2.38 to 4.18 MW/m2. Under the heat flux of 2.38 MW/m2, the coating remained intact because of its low surface temperature and the pinning effect of the newly formed HfSiO4 and ZrSiO4 phases. With an increase in the heat flux, the surface temperature increased beyond the melting point of HfO2 and ZrO2 and the coating suffered a violent flush of the oxyacetylene torch, which resulted in severe evaporation of the oxides and the weakening of the pinning effect.