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HfB 2 -SiC coatings with 30–60 wt% HfB 2 additions were prepared by slurry-dipping on SiC-coated C/C composites for investigating their oxidation behavior at low (1173 K) and high (1773 K) temperatures. With the increase of HfB 2 content, more B 2 O 3 glass was produced in the coating and the coating became denser during oxidation at 1173 K. 50 wt% HfB 2 -SiC coating can protect C/C composites for 494 h against oxidation, which was attributed to the formation of the dense borosilicate glass with high thermal stability as an oxygen barrier layer. After oxidation at 1773 K, 30 wt% HfB 2 -SiC coating provided the longest protection time (460 h) for C/C composites among 30–60 wt% HfB 2 -SiC coatings. A few Hf-oxides inhibited the volatilization of SiO 2 glass as the main phase in the 30 wt% HfB 2 -SiC coating after oxidation. As for other coatings with higher content of HfB 2 , the violent oxidation of HfB 2 particles made more bubbles produced, resulting in the poor oxidation resistance at 1773 K. [ABSTRACT FROM AUTHOR]