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

Abstract

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)O2 and (Hf, Zr)6Ta2O17 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 (HfO2, ZrO2 and Ta2O5) of TaC-modified HfC-ZrC coatings during ablation. As for HfC-ZrC coating, the formed (Hf, Zr)O2 skeleton was loose and hard to resist long-term ablation (less than 180 s). A small amount of Ta2O5 diffused to (Hf, Zr)O2 and produced the stable and dense Ta-doped (Hf, Zr)O2 and (Hf, Zr)6Ta2O17 oxide films, increasing the ablation resistance of the HfC-ZrC-TaC coating (5:5:1, more than 180 s). Excessive Ta2O5 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).