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.