Multilayer oxidation protective coating for C/C composites from room temperature to 1500 °C

To prevent carbon/carbon (C/C) composites from oxidation, a multilayer oxidation resistant coating was prepared. The inner SiC coating was prepared by pack cementation, and the outer SiC-MoSi₂ three-layer coating was obtained by slurry coating using silicon-sol as the caking agent. X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy were used to analyze the phase, microstructure and element distribution of the as-prepared coating. The results show that, the as-received multilayer coating has a crack-free structure with the thickness of about 300 μm. It is provided with excellent oxidation resistance from room temperature to 1500 °C in air and can protect C/C composites from oxidation for more than 120 h at 900 °C and more than 110 h at 1500 °C in air. The weight loss of the coated samples during oxidation tests mainly resulted from the oxidation of Mo₅Si₃ and the volatilization of SiO₂ in the coating.