TaxHf1−xB2–SiC multiphase oxidation protective coating for SiC-coated carbon/carbon composites

•TaxHf1−xB2–SiC coating was prepared on SiC coated C/C by in-situ reaction method.•TaB2 and HfB2 were introduced in the form of solid solution TaxHf1−xB2.•The coating could protect C/C for 1480 h with only 0.57% mass loss at 1773 K in air.•Oxidation layer consists of out Ta–Si–O compound layer and inner SiO2 glass layer.•Ta–Si–O compound silicate layer presents a better stability than SiO2 glass layer.

A TaxHf1−xB2–SiC coating was prepared by in-situ reaction method on SiC coated C/C composites. TaxHf1−xB2 phase is the form of solid solution between TaB2 and HfB2. Isothermal oxidation behavior at 1773 K and ablation behavior of the coated C/C were tested. TaxHf1−xB2–SiC/SiC coating could protect the C/C from oxidation at 1773 K for 1480 h and ablation above 2200 K for 40 s. During oxidation, oxides of Ta and Hf atoms exist as “pinning phases” in the compound glass layer consisted of outer Ta–Si–O compound silicate layer and inner SiO2 glass layer, which was responsible for the excellent oxidation resistance.