Residual stress and ablation behavior of CVD TaC coatings on graphite

This study investigates the residual stress and oxyacetylene ablation behavior of CVD TaC coatings on graphite in detail. TaC coatings with hybrid orientations were prepared by isothermal chemical vapor deposition with a TaCl5–H2–Ar–C3H6 system in 1800 °C. The hardness and elastic modulus of the TaC coating were calculated to be 18.635 GPa and 288.7 GPa, respectively. The CVD TaC coating was dense, and the grains appeared as bumps with smooth surfaces. X-ray diffraction characterized the residual stress of the TaC coating, and the result showed that compressive stress with a value of 186.3 MPa existed in the coating. The TaC coating has excellent ablation resistance, and its linear ablation rate is only 0.17 μm/s. After ablation, three distinct ablation regions with different morphologies, marked as the center, transition, and outer regions, were formed on the coating surface. The ablation products were mainly composed of a low-temperature phase (β-Ta2O5) and a high-temperature phase (α-Ta2O5), and their components were different in the three regions.