Abstract
A nanostructured SiC/SiC-ZrO2 coating was prepared on a graphite substrate by a two-step technique to improve the oxidation protection ability of graphite. The first step was to prepare a functionally graded SiC layer by a pack cementation process and the second one was to obtain a SiC-ZrO2 coating through a pack cementation technique at 1873K. The phase compositions and microstructure of the coating were characterized by X-ray diffraction and scanning electron microscopy. The isothermal oxidation test of the coated samples was performed at 1773K for 10h. A gradient C–SiC transition layer can be observed at the graphite-coating interface and a SiC-ZrO2 coating was formed. The SiC nanofibers with the diameter in the range of 30–160nm were observed on the coating. The SiC-ZrO2 coating could efficiently improve oxidation resistance of graphite with a weight loss of 11%, as compared with a 70% weight loss of the first step coating.
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