The oxidation behavior of MoSi2-CrSi2-Si/SiC coating for C/C composites in H2O-O2-Ar atmosphere: Experiment and first-principle investigation

The MoSi2-CrSi2-Si/SiC multi-component coating was prepared by two-step pack cementation on carbon/carbon composites. To investigate the effect of water vapor on the anti-oxidation of the coated samples, two kinds of atmosphere (50%H2O-50%O-2, 50%O-2-50%Ar) were designed for comparison with a total pressure of 1 atm at 1773 K. The results showed that, after being tested for 10 h, the weight loss of the coated samples in O-2+Ar and H2O+O-2 were 0.243% and 0.436% respectively. The reasons for different weight losses can be attributed to the water vapor, which could degrade the protective ability of the glass layer formed by SiO2 and Cr2O3 and thereby accelerate the oxidation of MoSi2 and CrSi2. Based on the Mulliken analysis calculated by the first principle, the corresponding water vapor corrosion resistance of the prepared coating was in the following order: SiC > MoSi2 > CrSi2, which was consistent with the experimental phenomenon.