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 degrees C to 800 degrees C. 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 degrees C-1000 degrees C) and fastest oxidation region (1000 degrees C-1280 degrees C). The enhanced oxidation activity of SiC above 1000 degrees C 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 degrees C. 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.