Formation mechanism and oxidation behavior of MoSi₂-SiC protective coating prepared by chemical vapor infiltration/reaction

In order to protect C/C composites from oxidation, SiC-MoSi₂ composite coating was synthesized by chemical vapor infiltration /reaction (CVI/CVR) technology. A porous Mo layer was prefabricated on SiC coated C/C composites, and then MoSi₂ and SiC were subsequently prepared in a CVI /CVR process using methyltrichlorosilane (MTS) as precursor. The deposition and reaction mechanism of the MoSi₂-SiC composite coating was investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The oxidation behavior of SiC-MoSi₂ coated specimens was tested. The results show that the porous Mo layer can be densified with SiC phase decomposed from MTS, and transformed into SiC-MoSi₂ by reacting with MTS as well. A dense composite coating was prepared with optimized deposition parameters. The coated specimen exhibits a good oxidation resistance with a little mass loss of 1.25% after oxidation at 1500 C for 80 h.