Effects of microstructures on the ablation behaviors of ZrC deposited by CVD

Through changing the H₂ concentrations in the H₂+Ar dilution gas, different microstructures of ZrC coatings were prepared on carbon/carbon (C/C) composites by low pressure chemical vapor deposition (LPCVD) using ZrCl₄-C₃H₆-Ar system. The effects of microstructure on anti-ablation behaviors of the ZrC coating under oxyacetylene torch were investigated. Results show that the preferred orientation of ZrC coatings transforms from (111) to (200) to (220) and the particle size decrease from micro-scales to nano-scales as the H₂ concentrations increase. After ablation for 100s, the coating with in-situ nanoparticles characterized by the (200) preferred orientation exhibits the lowest ablation rates among four samples, which the linear and mass ablation rates were 0.25×10^-3mm/s and 0.88×10^-4g/cm²/s, respectively. The good ablation resistance of the coating is mainly attributed to the formation of the dense and crack-free ZrO₂ layer with ZrO₂ nanorods during the ablation.