Ablative Property and Mechanism of ZrC-TaC/ZrC-SiC Coatings on C/C Composites under Different Heat Fluxes

In high-temperature aerobic environment, carbon materials have to be protected to delay the oxidation process. In this work, ZrC-TaC coatings were deposited by supersonic atmospheric plasma spraying on ZrC-SiC-coated C/C composites and ablation tests were conducted by oxyacetylene torch under different heat fluxes. When subjected to 4.2 WM/m2 for 20 s, the mass and linear ablation rates of the ZrC-TaC/ZrC-SiC coating system were 0.0076 g/s and 0.0005 mm/s, respectively. In the ablation process, the infiltration of the oxygen and liquid Ta2O5 into the inner layer resulted in significant oxidation of the ZrC-SiC inner layer. Due to the oxidation and microstructure evolution of the ZrC-TaC and ZrC-SiC layers, the porous Zr-Ta-O oxide layer, oxidized ZrC-TaC, and ZrC-SiC layers formed a better chemical combination and showed higher resistance to ablation. However, for a heat flux of 3.2 WM/m2, the molten Zr-Ta-O oxides that have good self-healing ability, were mainly formed on the ablative surface; liquid Ta2O5 together with trace oxygen could penetrate into the inner layers, resulting in the lack of chemical combination between the layers. As a result, the molten oxides were easy to denudate during the ablation and cooling process and showed lower resistance to ablation.

Automated summary

The study demonstrates that in high-temperature aerobic environment, the ZrC-TaC/ZrC-SiC coating system can effectively protect carbon materials from oxidation and improve ablation resistance. However, at lower heat flux, inadequate chemical combination between the layers can result in reduced overall resistance to ablation.