To protect graphite materials from oxidation, a dense (ZrTa)B2–SiC–Si coating was for the first time prepared on graphite substrate by slurry dipping and vapour silicon infiltration process. (ZrTa)B2 phase was synthesised by in-situ reaction using ZrC, TaC, B4C, phenolic resin and Si as raw materials. The phase compositions and microstructure of the obtained coating were analysed by XRD and SEM. The isothermal oxidation tests demonstrated that the in-situ coating had excellent oxidation resistance ability, after oxidation for 468 and 347 h at 1273 and 1773 K, respectively, the weight gains were 0.07% and 0.33%, respectively. No signs of oxidation of graphite substrate were found after oxidation, and two layers could be observed in the coating, namely, oxide layer containing Zr and Ta oxides and (ZrTa)B2–SiC–Si layer. A model for the evolution of the oxide layer was proposed to interpret the oxidation failure mechanism of the coating.
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