Effects of SiC coating on ablation resistance of carbon fibre reinforced BN–Si3N4 matrix composite

Abstract

A SiC coating was prepared on the surface of a carbon fibre reinforced BN–Si₃N₄ composite by chemical vapour deposition. The coating was characterised by SEM and XRD, and the ablation behaviours of the coated and uncoated composites were investigated and compared. The coating is mainly amorphous SiC and quite compact; the ablated area of the composite is reduced considerably by the coating and the coated composite presents a lower linear ablation rate of 21˙4% and a lower mass ablation rate of 51˙6%. The SiC coating covers over the pores on the surface of the ablative composite, which prevents the flame from spreading to other regions and from penetrating the inside of the composite. As a result, both the chemical erosion and the mechanical denudation are restrained and the ablation resistance of the composite is improved.