Oxidation and ablation resistance of SiC/ZrB2-SiC-B4C coatings for C/SiC composites

Abstract:

Carbon/silicon-carbide composites (C/SiC) usually suffer from high-temperature oxidation and ablation. In this study, double-layered SiC/ZrB2-SiC-B4C coatings were fabricated by chemical vapor deposition (CVD) and slurry painting-sintering methods. The naked, single-SiC coated and SiC/ZrB2-SiC-B4C double-layered C/SiC composites were oxidized at 1500 °C and ablated under a heat flux of 4.2 MW/m2. The results indicated that the slurry-painted ZrB2-SiC-B4C coating was dense and intact, which had a surface roughness of ~ 1 μm in Ra and the porosity of ~ 4.2 %. After oxidation at 1500 °C for 30 h, the mass loss rate of SiC/ZrB2-SiC-B4C coated C/SiC composite was ~ 10 %. The oxidation scale on the coating surface is compact without obvious cracking. After ablation for 20 s, the linear and mass ablation rates of SiC/ZrB2-SiC-B4C coating were separately 1.0±0.3 μm/s and 1.1±0.2 mg/s, decreased by 75.0 % and 50.0 % relative to the SiC coating. The formed ZrO2-SiO2 scale provided a protection against the mechanical erosion from the flame.

Key words:C/SiC composites; Coating; Slurry painting; Oxidation; Ablation