The synergistic effect of multi-phase oxides on the ablation resistance of TaC-modified HfC-ZrC coatings for C/C composites.

Traditional HfC- and ZrC-based coatings for C/C composites had loose oxide films after long-term ablation, limiting their application above 2000 ℃. In this work, through adjusting the TaC content, the formation of stable and dense Hf-Zr-Ta-O compound films composed of Ta-doped (Hf, Zr)O 2 and (Hf, Zr) 6 Ta 2 O 17 prolonged the service life of HfC-ZrC coating. Additionally, the first-principle calculation based on the VASP software helped to understand the solid solution process among multi-component oxides (HfO 2 , ZrO 2 and Ta 2 O 5) of TaC-modified HfC-ZrC coatings during ablation. As for HfC-ZrC coating, the formed (Hf, Zr)O 2 skeleton was loose and hard to resist long-term ablation (less than 180 s). A small amount of Ta 2 O 5 diffused to (Hf, Zr)O 2 and produced the stable and dense Ta-doped (Hf, Zr)O 2 and (Hf, Zr) 6 Ta 2 O 17 oxide films, increasing the ablation resistance of the HfC-ZrC-TaC coating (5:5:1, more than 180 s). Excessive Ta 2 O 5 was damaged by mechanical denudation during ablation, failing HfC-ZrC-TaC coatings (3:3:1 less than 180 s and 1:1:1 less than 120 s). • The oxidation of TaC lagged behind HfC/ZrC and the oxidation sequence of these elements was Hf ≥ Zr ＞ Ta. • Through first-principle calculations, VASP was used to study the solid solution process among multi-oxides during ablation. • The formation of the stable Hf-Zr-Ta-O compound film increased the ablation resistance of HfC-ZrC-TaC-related coatings. [ABSTRACT FROM AUTHOR]