Microstructure and oxidation resistance of SiC-MoSi₂ multi-phase coating for SiC coated C/C composites

In order to improve the anti-oxidation of C/C composites, a SiC-MoSi₂ multi-phase coating for SiC coated carbon/carbon composites (C/C) was prepared by low pressure chemical vapor deposition (LPCVD) using methyltrichlorosilane (MTS) as precursor, combined with slurry painting from MoSi₂ powder. The phase composition and morphology were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD) methods, and the deposition mechanism was discussed. The isothermal oxidation and thermal shock resistance were investigated in a furnace containing air environment at 1500°C. The results show that the as-prepared SiC-MoSi₂ coating consists of MoSi₂ particles as a dispersing phase and CVD-SiC as a continuous phase. The weight loss of the coated samples is 1.51% after oxidation at 1500°C for 90h, and 4.79% after 30 thermal cycles between 1500°C and room temperature. The penetrable cracks and cavities in the coating served as the diffusion channel of oxygen, resulted in the oxidation of C/C composites, and led to the weight loss in oxidation.