Life prediction of 3D woven C-SiC composites at high temperatures with low-frequency cyclic stresses

The corrosion of a C-SiC composite with SiC coating (SiC-C/SiC) is studied under a low-frequency cyclic stress in various gas atmospheres of oxygen, water vapor, and sodium sulfate vapor at temperatures from 1000 to 1300°C. A model for the cyclic stress corrosion mechanism of the composite is proposed from the experimental study. An equation to predict the lifetime of the composite under cyclic stress conditions is derived from the model. It is found that under cyclic stress conditions, oxygen is the only major factor degrading the composite and the corrosion kinetic is controlled by the carbon-oxygen reaction. The validity of the model and the equation is confirmed well by the experimental results.