C/SiC/MoSi₂-Si multilayer coatings for carbon/carbon composites for protection against oxidation

To improve the oxidation resistance of carbon/carbon (C/C) composites, a C/SiC/MoSi₂-Si multilayer oxidation protective coating was prepared by slurry and pack cementation. The microstructure of the as-prepared coating was characterized by scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy. The isothermal oxidation and erosion resistance of the coating was investigated in electrical furnace and high temperature wind tunnel. The results showed that the multilayer coating could effectively protect C/C composites from oxidation in air for 300h at 1773K and 103h at 1873K, and the coated samples was fractured after erosion for 27h at 1873Kh in wind tunnel. The weight loss of the coated specimens was considered to be caused by the formation of penetration cracks in the coating. The fracture of the coated C/C composites might result from the excessive local stress in the coating.