Reactivity of a C/SiC composite in water vapour

The reactivity at high temperature of C/SiC composites is studied in water vapour and is compared with the one in oxygen. In particular, the respective part of the carbon gasification and SiC oxidation in the oxidation of the composite was determined by using a method which combines gravimetrical and gas phase composition measurements. Experimental results point out that C and SiC in the composite are significantly oxidized in water vapour, the carbon gasification being widely predominant. It has been also shown that the oxidation of the SiC matrix is strongly enhanced in water vapour, but this is not sufficient for acting as an oxidation barrier. It appears that others parameters like the presence of microfissures, the non-homogeneous covering of the carbon material in the composite play also a very important role. The obtained experimental results were confirmed by SEM observations.