Thermal shock resistance and isothermal oxidation behavior of C/SiC-SiCnano functionally gradient coating on graphite produced via reactive melt infiltration (RMI)

A C/SiC-SiCnano functionally gradient coating was prepared on graphite by reactive melt infiltration (RMI) at 1873 K under argon atmosphere. The phase composition, microstructure, isothermal oxidation behavior and thermal shock resistance of the coatings were investigated. The results showed the presence of alpha-SiC and beta-SiC phases as well as a little amount of Si in the coating. The addition of SiC nanoparticles resulted in surface continuity improvement and increase transition interface thickness. Isothermal oxidation test was performed at 1773 K for 10 h in air. Results showed with increasing the SiC nanoparticles content the weight loss of the samples dropped from 48.72% to 5.03%. Despite the results of the isothermal oxidation test, the samples without SiC nanoparticles exhibited the minimum weight loss after thermal cycling oxidation between 1773 K and room temperature for 14 times due to the formation of SiC whiskers. (C) 2016 Elsevier B.V. All rights reserved.