Effects of water vapor on corrosion behaviors of C/SiC in oxidizing atmosphere containing Na2SO4 vapor

Corrosion of a C/SiC composite has been investigated in the atmosphere containing oxygen, water vapor and sodium sulfate vapor at the temperatures range from 1000 to 1500 °C. The effect of water vapor on the corrosion mechanism of C/SiC were discussed based on the weight change, the residual strength change, the microstructure and calculated results from FactSage. The corrosion of C/SiC is attributed to (i) the permeation of gas through the SiO2 film below 1300 °C, (ii) the diffusion of oxidant through pores caused by bubbles broken in the SiO2 film above 1300 °C. The water vapor does not change the corrosion mechanism of C/SiC composite but the temperature range in which the corrosion mechanism works by accelerating the oxidation of SiC and the corrosion of SiO2.