Ablation behavior of HfC coating with different thickness for carbon/carbon composites at ultra-high temperature

The thickness of the different HfC coatings from 20 μm to 50 μm were prepared on the surface of carbon/carbon (C/C) composites by low pressure chemical vapor deposition (LPCVD). The microstructure and thermal stress of the coatings after ablation were investigated, as well as the effect of thickness and thermal stress on the ablation resistance of the HfC coating was analyzed. After being ablated at a heat flux of 2.4 MW/m² for 60 s, the thermal stress gradually increased at first and then rapidly increased with the increasing thickness of coating. The results indicated that the moderate coating thickness can effectively release the thermal stress generated during the ablation process. The 40 μm-thick HfC coating showed the best ablation resistance with the mass ablation rate and line ablation rate were only 0.13 mg/s and 0.09 μm/s, respectively.