Oxidation behaviour of interlocking SiC–Si coating for graphite prepared by preoxidation and gaseous silicon infiltration process

Abstract

An interlocking SiC–Si coating on graphite was fabricated by a method combining preoxidation and gaseous silicon infiltration processes. The effect of preoxidation time on the microstructures and oxidation behaviour of the coating was investigated. After preoxidation of graphite at 900 °C for 10 min, the thickness of the as-obtained SiC–Si coating increased from 35 μm to 80 μm, and the penetration depth of the SiC–Si phase was up to several hundred microns. The isothermal oxidation test at 1500 °C suggested that the mass loss of coated graphite decreased from 5.42% after 6 h to 1.28% after 110 h, and the 15 times thermal shock test between 1500 °C and room temperature suggested that the mass loss decreased from 13.20% to −0.34% because of preoxidation. The improved oxidation performance is ascribed to the fact that the interlocking structure of the SiC–Si coating alleviates crack propagation during oxidation, and a large amount of glassy SiO2 produced on the thick SiC–Si layer migrates and seals the defects in the coating. It is believed that the construction of an interlocking structure offers a technological basis to produce oxidation protective coatings for carbon-based materials in high-temperature applications.