Comparative analysis of oxidation resistance at 1700 °C for HfB2-SiC-MoSi2 coatings on curved C/C composites prepared via gaseous and liquid silicon infiltration

To investigate the differences in densification effects and oxidation resistance of curved samples subjected to gaseous and liquid Si infiltration, HfB 2 -SiC-MoSi 2 -Si/SiC-Si coated C/C composites are prepared using gaseous and liquid Si infiltration (G-HSM and L-HSM), respectively. The mass change rates of G-HSM and L-HSM after thermal shock from 1700 ​°C to room temperature are −2.52 ​% and 0.07 ​%. After isothermal oxidation at 1700 ​°C for 200 ​h, the mass change rate of L-HSM is −0.12 ​%, while that of G-HSM reaches −0.60 ​% after 124 ​h. The high content of HfB 2 and MoSi 2 in L-HSM improves the coating stability, which effectively avoids droplet shedding. In addition, the lower roughness and narrower original cracks reduce oxygen adsorption sites and diffusion channels of L-HSM during oxidation. Thus, L-HSM exhibits better thermal shock resistance and oxidation resistance than G-HSM. This study provides a strategy for the coating design of curved components above 1700 ​°C.