Ablation resistance of TaC-modified HfC coating prepared by supersonic plasma spraying for SiC-coated carbon/carbon composites

A HfC-TaC composite coating was prepared on SiC-coated C/C composites by supersonic atmosphere plasma spraying (SAPS) to improve their ablation resistance. The ablation resistance was evaluated under oxyacetylene torch with heat flux of 2.38 MW/m² and 4.18 MW/m² respectively, and the effect of TaC on microstructure and phase composition of the coating was investigated. Results showed that TaC-modified HfC coating exhibited good ablation resistance under the torch with heat flux of 2.38 MW/m² and its mass and linear ablation rates were -0.35 mg/s and -1.05 μm/s separately, which is ascribed to the formation of continuous oxide film including phases like Hf₆Ta₂O₁₇ and Ta₂O₅. Crack propagation in the coating was inhibited due to the phase transition restriction of HfO₂ by Ta₂O₅, and cracks and holes in the oxide layer could be repaired by molten Ta₂O₅ and Hf₆Ta₂O₁₇. However, the occurrence of ablation crater on the surface of HfC-TaC coating is mainly attributed to the unsatisfactory scouring resistance of the oxide film under heat flux of 4.18 MW/m².