High temperature oxidation and corrosion of silicon-based non-oxide ceramics

The present study is focussed on the oxidation behavior of nonoxide silicon-based ceramics. Various Si3N4, and SiC ceramics were examined after long term oxidation tests (up to 5000 h) at 1500 degrees C in ambient air. The damage mechanisms were discussed on the basis of a comprehensive chemical and microstructural analysis of the materials after the oxidation tests. The diffusion of oxygen into the material and its further reaction in the bulk of the material were found to be the most critical factors during long term oxidation treatment at elevated temperatures. However, the resulting damage in the microstructure of the materials can be significantly reduced by purposeful microstructural engineering. Using Si-3/N-4/SiC and Si3N4/MoSi2 composite materials provides the possibility to improve the high temperature stability.