The improvement in oxidation resistance of CVD-SiC coated C/C composites by silicon infiltration pretreatment Original Research Article

Silicon infiltration pretreatment has been used to improve the high-temperature oxidation resistance of CVD-SiC coated C/C composites. C/C composites were infiltrated with silicon in an Ar atmosphere and then coated with CVD-SiC coating to a thickness of ca 50 μm. Isothermal and cyclic oxidation tests at 1500 on the CVD-SiC coated C/C composites with and without silicon infiltration pretreatment were carried out in methane-combusted exhaust gas. C/C composites directly coated with CVD-SiC coating exhibited a large mass loss. However, for C/C composites with silicon infiltration pretreatment, very low mass losses were observed. The functionally gradient SiCC conversion layer played an important role in minimizing the thermal expansion mismatch between the SiC coating and the substrate and in improving the chemical compatibility of the substrate with the CVD-SiC coating. As a result of this, the cracks induced by the thermal expansion mismatch stayed within the SiCC conversion layer, and the oxidation through these cracks was considerably limited.