In order to improve the oxidation resistance of the C/ C composites, a SiC/ SiO2 coating was prepared
by pack cementation and low pressure CVD. The microstructures of the multilayer coating were studied by XRD, SEM and EDS analyses, and then the oxidation resistance of the as coated C/ C composites was evaluated in ambient air at 1 273 K and 1 773 K. The results show that the SiC coating prepared by pack cementation has a compositional gradient. And the external amorphous SiO2 coating prepared by low-pressure CVD effectively seals the cracks and holes of the internal SiC coating. Furthermore, the problem that an integral SiO2 film can not be formed by the oxidation of SiC coating at medium temperature (1 073 to 1 473 K) also is solved. After oxidation in ambient air at 1 273 K and 1 773
K for 10 h, the mass losses of the ascoated C/ C composites are only 4. 97 mg/ cm2 and 0. 36 mg/ cm2, respectively.The SiC/ SiO2 coating shows excellent anti-oxidation property.