Oxidation behaviors of C/SiC in the oxidizing environments containing water vapor

Compared with those in oxygen/argon mixtures, the oxidation behaviors of C/SiC materials are studied in H2O/argon gas mixtures and in H2O/O2/argon mixtures, respectively. By measuring the thickness of the SiO2 scale formed on the SiC coating, the oxidation parabolic rate constants and the activation energies of CVD SiC are calculated. Experimental results point out that the oxidation of the SiC matrix is strongly enhanced in the environments containing water vapor. By microscopy observations and XRD analysis, the stresses in the silica scale are studied. By thermo-gravity analysis, the oxidation kinetics of C/SiC materials is investigated. The weight loss of C/SiC materials in H2O/O2/argon mixtures is smaller than in dry oxygen with the same oxygen partial pressure, because the apparently formed SiO2 scale in H2O/O2/argon mixtures acts as an effective oxidation barrier.