Dynamic oxidation protective behaviors and mechanisms of HfB2-20wt%SiC composite coating for carbon materials

HfB₂-20%wtSiC composite coating was prepared by liquid phase sintering method. After modification of HfB₂ phase, the initial oxidation consumptions of the SiC coated samples were delayed from 500 ℃ to 800 ℃. Due to the higher oxidation activity of HfB₂, the sufficient generated B₂O₃ is capable of inhibiting oxidation consumption of carbon substrate in oxidation activation region (800 ℃-1000 ℃) and fastest oxidation region (1000 ℃-1280 ℃). The enhanced oxidation activity of SiC above 1000℃ leads to the increased generation of SiO₂, inhibiting the evaporation of B₂O₃ through the formation of Hf-B-Si-O glass layer, improving its stability and oxidation resistance above 1000℃. The heterogeneous refractory Hf-Oxides embedded in Hf-B-Si-O glass layer play role of reinforcement phases, restricting generation and spread of cracks. The inerting effect of Hf-B-Si-O glass layer strengthened with the increase of thermogravimetric analysis (TG) recycle oxidation times, indicating promising oxidation inhibition potential of the coating in dynamic aerobic environment.