Effect of pre-oxidation on the ablation resistance of ZrB₂-SiC coating for SiC-coated carbon/carbon composites

To improve ablation resistance of carbon/carbon (C/C) composites at high temperature, ZrB₂-SiC coating was prepared on surface of SiC-coated C/C composites by supersonic atmosphere plasma spray. The coated C/C composites were pre-oxidized in air at 1373 K. In the present work, the influence of pre-oxidation treatment on the microstructure and ablation resistance of ZrB₂-SiC coating was investigated. Ablation resistance of coated C/C composites was tested in oxyacetylene torch environment with the heat flux of 2400 kW/m². Results show that the liquid glass phase seals defects in the as-sprayed coating after pre-oxidation for 15 min and a dense coating is obtained. The pre-oxidation coating can protect C/C composites for 90 s, which is due to the formation of a dense oxides layer and the molten ZrO₂ layer.