Effect of heat treatment on the microstructure and properties of CVD SiC fiber

In this study, the effect of heat treatment on the room temperature strength of W-core SiC fiber produced by chemical vapor deposition (CVD) was investigated. Thermal exposure in the temperature range of 900-1000 °C decreases the strength of the SiC fiber. Fracture morphology analysis indicates that failure initiations predominantly take place at the W-core/SiC interface. A reaction layer that formed at the W-core/SiC interface during thermal exposure degraded the fiber strength and an empirical linear relationship of strength vs thickness of the reaction layer can be obtained. The kinetics of the growth of the W-core/SiC reaction layer were determined.