Corrosion of Nonoxide Silicon-Based Ceramics in a Gas Turbine Environment

In the present study the corrosion behavior of nonoxide silicon-based ceramic materials was investigated. Hot gas tests were conducted on silicon nitride and silicon carbide materials in an atmosphere similar to that in a gas turbine. While some materials displayed a high degree of microstructural stability, all materials suffered surface degradation during the rig test. The oxidation surface layer of mainly Si02, which is essential for the oxidation protection of nonoxide materials because it induces a passive, diffusion-controlled oxidation mechanism, was found to be degraded by evaporation processes involving volatile silicon hydroxides. The partial pressure of steam was found to be the most important factor governing these processes.