To protect carbon materials from oxidation, SiC coatings were prepared on carbon/carbon (C/C) composites and graphite by the chemical vapor reaction (CVR) in the same condition. Microstructure of the as-prepared coating was studied by using XRD, SEM and EDS analyses. The influence of different carbon substrates on the structure and surface morphology of the SiC coating was discussed, and then the oxidation resistance of the two obtained samples was tested and compared. The results show that: though the two as-prepared coatings are compact and have a good bonding ability with substrate, they reveal an obvious structure difference. The obtained SiC coating on graphite shows a gradient distribution, which consists of the dense out-layer and inner transitional layer; while the coating on C/C composites only reveals a dense out-layer structure. The oxidation test indicates that the SiC coated graphite exhibits better anti-oxidation property than the SiC coated C/C composites, and after oxidation in air at 1823 K for 30 h and the thermal cycling between 1823 K and room temperature for 7 times, the weight loss of the coated graphite is only 0.182%.

Key words: carbon/carbon composites, graphite, anti-oxidation coating, SiC