Ultra-high-temperature ceramic TaB2-SiC-Si coating by impregnation and in-situ reaction method to prevent graphite materials from oxidation and ablation

Abstract A monolayer TaB2-SiC-Si protective coating was fabricated by impregnation and in-situ reaction method on the surface of graphite to prevent graphite materials from oxidation and ablation, and the microstructure, oxidative and ablative protection properties of the coating were investigated. Experimental results revealed that the coating could protect graphite from oxidation at 1020 °C and 1550 °C for more than 321 h and 168 h, respectively, and from ablation for 120 s with a heat flux of 2.38 MW/m2. The good oxidative protection performance was ascribed to the low oxygen diffusivity of the coating and oxide film formed on the coating surface, which effectively inhibited oxygen diffusion to the graphite substrate. Under oxyacetylene flame, a Ta2O5 layer was gradually formed on the coating surface and acted as a protective layer, which weakened the erosion of flame to the inner coating. The increase of ablative time promoted the fierce evaporation of gaseous Si and oxide phases, such as B2O3(g), SiO2(g), CO(g) and CO2(g), which resulted in the damage to the TaB2-SiC-Si coating, leading to the reduction of anti-ablation property of the coating.