High‐Temperature Stability of SiC‐Based Composites in High‐Water‐Vapor‐Pressure Environments

Abstract

Microstructural characterization of boron‐containing SiC‐reinforced SiC composites exposed at high temperature in high‐water‐vapor‐pressure environments was used to determine surface recession rates and to understand the controlling degradation processes under these conditions. Results showed that composite degradation was controlled by a series of reactions involving the formation of silica, boria, borosilicate glass, and gaseous products. Comparison of results (from characterization of composites exposed at 1200°C and 1.5 atm of H2O in a laboratory furnace and in the combustion zone of a gas turbine) showed that these reactions were common to both exposure conditions and, consequently, there was little effect of gas velocity on degradation rates of boron‐containing SiC/SiC composite materials.