The oxidation resistance of two-temperature synthetic HfB2-SiC coating for the SiC coated C/C composites

To explore oxidation resistance of HfB2-SiC coatings, the HfB2-SiC coating was prepared at 2173 K (sample A) and 2373 K (sample B) by in-situ synthesis for SiC coated Carbon/carbon (C/C) composites. Compared with sample A, HfB2 phases of sample B are more and the coating is thicker. At 1773 K in air, the C/C substrate of sample A can be protected for 319 h with 1.63% weight loss percentage, while the C/C substrate of sample B can be protected for 753 h with only 0.487% weight loss percentage, which indicates that 2373 K is easier to generate HfB2 phases and beneficial to protect samples from oxidation. After 40-time thermal cycle, the weight loss percentages of sample A and B are 1.85% and 0.78%, respectively, which reveals that the latter has a better thermal shock resistance. •The outer HfB2-SiC coatings were prepared at 2173 K (A) and 2373 K (B).•The C/C substrate was protected for 753 h by sample B at 1773 K in air.•2373 K is easier to generate HfB2 phases than 2173 K.