Mortise-tenon structure of caterpillar-like SiC transition layer enhancing interfacial bonding and ablation resistance of Hf-Ta-C coating

The poor interfacial bonding between Cf/SiC composites and ultra-high temperature ceramic coatings prepared by Supersonic Atmosphere Plasma Spraying (SAPS) restricted the application of the composites in the ultra-high temperature field of aerospace. To solve this problem, a caterpillar-like SiC transition layer with a rough surface was fabricated on the Cf/SiC composites by Chemical Vapor Deposition (CVD). Afterwards, the HfTaC2 coating was prepared on the surface of the SiC transition layer by SAPS. In this way, a mortise-tenon joint was constructed between the “caterpillar-like” SiC transition layer and the HfTaC2 coating. The effect of the SiC transition layer with the mortise-tenon structure on the microstructure, bonding strength, and ablation resistance of the HfTaC2 coatings was investigated. Results show that the bonding strength was increased from 0.53 ± 0.3 MPa to 15 ± 1.7 MPa between Cf/SiC composites and HfTaC2 coatings after the introduction of the transition layer, which was ascribed to the mortise-tenon joint. Compared to the HfTaC2 coating (-6.33 μm·s-1), the SiC/HfTaC2 coating exhibited a lower linear ablation rate (-0.56 μm·s-1) after ablation with a heat flux density of 2.38 MW·m-2. The excellent ablation resistance of the dual-layer coating was attributed to the dense Hf-Ta-Si-O oxide layer, as well as the alleviation of thermal mismatch owing to SiC transition layer.