Structural evolution and ablation mechanism of a hafnium carbide coating on a C/C composite in an oxyacetylene torch environment

HfC coating was deposited on carbon/carbon composites by chemical vapor deposition. The evolution of morphology and microstructure of the coating during ablation is investigated and the ablation mechanism is proposed. Results show that the coating shows an outstanding ablation resistance. After ablation, three distinct regions (central, transitional and outer ablation region) can be detected on the coating surface. In the former two regions, four layers can be divided from the cross-section of the ablated coating. Both molten HfO2 and HfCxOy could act as oxygen diffusion barrier during ablation. Oxidation and mechanical erosion are main ablation behavior of the HfC coating.

The structure of the ablated coating in the transitional ablation region consists of four distinct layers. Both molten HfO2 and HfCxOy could act as an oxygen diffusion barrier to retard the further oxidation of the inner coating. Oxidation and mechanical erosion are the main ablation behavior.Figure optionsDownload as PowerPoint slideHighlights
► HfC coating was deposited on C/C composites by LPCVD using HfCl4–CH4–H2–Ar system.
► HfC coating shows outstanding ablation resistance in an oxyacetylene torch environment.
► Oxidation and mechanical erosion are the main ablation behavior of the HfC coating.
► Both molten HfO2 and HfCxOy could act as oxygen diffusion barrier during ablation.