Preparation of oxidation protective Hf0.2Ta0.8B2−x–SiC coating by in-situ reaction method on SiC-coated carbon/carbon composites

To improve the oxidation resistance of TaB2 or HfB2 based coating for C/C composites, an outer Hf0.2Ta0.8B2−x–SiC coating was prepared by in-situ reaction method on SiC coated C/C composites. Hf0.2Ta0.8B2−x was obtained through the in-situ reaction by reducing HfO2 and Ta2O5 using B2O3 and graphite. The coating could protect C/C from oxidation at 1773 K for 1220 h. Dual protection of the “inlaid phases” and compound glass layer is responsible for the excellent oxidation resistance of the coating. The double layer coating also presents a stable oxidation resistance at a wide range of temperature from room temperature to 1773 K.