Silicon carbide based plasma sprayed coatings

Coatings containing up to 66 vol.% of silicon carbide were deposited by plasma spray. Potential applications can be found in the protection of CMC (ceramic matrix composite) against wear and high temperature oxidation. It is well known that SiC cannot be deposited by thermal spray because it decomposes before melting. To face this problem, a mixture of SiC and ZrB2 was deposited, since those two compounds form a eutectic phase, at a temperature lower than the one of SiC decomposition. Coating microstructure was characterized by XRD, SEM, and EDS, confirming the presence of SiC in the deposited layer and the formation of the eutectic phase during spraying. Samples of the coatings were exposed in air at high temperature, in the range of 650 °C to 1700 °C. The oxide scale was investigated by means of XRD, SEM, EDS and WDS. It was constituted by a SiO2 layer, which includes islands of ZrO2. Test results showed the good potential of the material investigated to be used as a protection against the high temperature oxidation.