Oxygen blocking enhancement of HfB2-SiC coating using HfB2-HfSi2 alloyed composite powders by self-propagating high-temperature synthesis

To suppress the oxidation loosening of HfB2-SiC coating, the HfB2 was alloyed with HfSi2 in the form of composite powders through self-propagating high-temperature synthesis (SHS) technique, which was then used to prepare HfB2-HfSi2-SiC coatings. Compared to the 60HfB2-SiC coating, the 60(HfB2-HfSi2)SHS-SiC coating exhibited lower oxidation activity and better inert oxygen blocking at 1700 degrees C. The addition of HfSi2 promoted the homogenization of the Hf-oxides distribution on the glass layer and the formation of the protective phase HfSiO4, further inhibiting oxygen diffusion. The 60(80HfB2-20HfSi2)SHS-SiC coating exhibited optimal oxygen blocking protection after oxidation at 1700 degrees C, with 87.96% and 92.33% reductions in oxygen permeability and carbon loss rate, respectively.