Preparation And Properties Of ZrB₂-SiC Based Ceramic Coating On C/C Composites

:To improve the anti-oxidation ability under different high temperature conditions,ZrB2-SiC based coatings were prepared by slurry painting on C/C and C/C-SiC composies,the SiC coating was prepared on the top of the coating system by chemical vapor deposition(CVD).The main work and conclusions are as follows.(1)Reactive sintering Zr-Si-B4C transition layer was prepared by slurry painting on C/C composite.The ZrB2-SiC-ZrC coating was prepared with this method,and part of the Zr,Si powders infiltrated into the C/C composite,the pining effect enhanced the interfacial bonding strength.But this method was effective only for the composites with a density below1.6g/cm3.Then the ZrB2-15vt%SiC-5vt%Si3N4(ZSS),ZrB2-15%vtSiC-10vt%MoSi2(ZSM),ZrB2-15vt%-20vt%TaC(ZST) coatings were prepared on the coated C/C composites and C/C-SiC composites by slurry painting.The CVD SiC outer coating was prepared on some of samples.(2)The900℃and1500℃isothermal anti-oxidation property were tested for the coatings.The coated C/C-SiC composites perfomed better at two temperature conditions.And the CVD SiC coating promoted the anti-oxidation property.The failure of the coating owed to the cracks caused by thermal shocks.(3)The anti-ablation property was tested by oxy-acetylene torch.The mass ablation rate were all negative for ZSS,ZSM and ZST coating.After30seconds ablation,ZSS coating has the lowest mass ablation rate of-5.08mg·s-1.After60seconds ablation,ZST coating has the lowest ablation rate of1.42mg·s-1.The CVD SiC coating had a negative influence on the anti-ablation property owing to the weak interfacial bonding with inner coating,the30s mass ablatin rate increased to0.40mg·s-1.The ablation mechanisms were different at different stages, chemical erosion and mechanical erosion work together in practical ablation environment.The formation of dense and high viscosity melt determines the ablation resistance of the coating system.