Oxidation behavior of 3D Hi-Nicalon/SiC composite exposed in wet and simulated air environments

Oxidation behavior of a 3D Hi-Nicalon/SiC composite was investigated in wet and simulated air with a flow rate of 3.5cms^-1 at temperatures above 1000°C. Results showed that oxidation was occurred mainly on the specimens surface and rate-controlled by oxygen diffusion for both oxidation environments. Silica formed in wet air was viscous and thicker. After oxidation, strength deterioration of the composite was associated mainly with the degradation of Hi-Nicalon fiber. Meanwhile, the difference in fracture behavior could be attributed to the change of fiber/matrix interface bonding caused by high temperature oxidation.