MoSi2-HfC/TaC-HfC multi-phase coatings synthesized by supersonic atmospheric plasma spraying for C/C composites against ablation

Highlights: • MoSi₂-HfC/TaC-HfC (MH/TH) bilayer coating were synthesized on SiC coated C/C composites by supersonic atmospheric plasma spraying. • The excellent ablation resistance of MH/TH coatings was attributed to the combination of TH and MH layers, the mass and linear ablation rate of MH/TH coatings were 0.236 mg/s and 1.026 µm/s, respectively. • The external TH layer could reduce the oxygen partial pressure for internal MH layer preventing the generation of destructive MoO₃. Besides, the formation of Mo₅Si₃ and SiO₂ not only block O₂ to slow down the generation of destructive region, but evaporates to reduce surface temperature. To improve the ablation resistance of C/C composites, MoSi₂-HfC/TaC-HfC (MH/TH) bilayer coatings were synthesized on SiC coated C/C composites. Results showed that the mass and linear ablation rate of MH/TH coatings were 0.236 mg/s and 1.026 µm/s, respectively. The excellent performance of MH/TH coatings was attributed to the combination of TH and MH layers. The external TH layer could create Ta₂O₅ and Hf₆Ta₂O₁₇ glassy phase to protect the internal layer and prevent the formation of destructive MoO₃. Meanwhile, the decomposition of the internal MH layer to produce SiO₂ diffusion outward could retard the destruction of the external coating.