Oxidation of SiC and Its Effect on the Interface Stability of SiC/Fe

The dense oxide layer is formed on the surface of sintered α-SiC after annealing at 1200℃ for 10h in a stationary air ambient, and its crystal structure is ofβ-cristobalite. The growth of the oxide layer is controlled by the diffusion of oxygen molecules through the interstitial site in SiO2. The solid state reaction between SiC and Fe is severe, and significantly decreases the interface stability of SiC/Fe. The oxidation of SiC has a great effect on the interface stability of SiC/Fe. At temperatures below 900℃, the interface of oxidized SiC/Fe is always smooth and remains intact after annealing for a long time. It shows that the oxide layer can hold back the interface reaction and improve the interface stability, permanently. But, the interface stability of O-SiC/Fe decreases corresponding to raising the annealing temperature. The reaction first takes place at the points of the interface, and then, wholly extends along the interface. It results that the effect of the oxide layer as a reaction barrier is lost entirely. The main reasons for the oxide layer invalid after annealing at the temperature above 900℃ may be the voids existed in the oxide layer, and the stress concentration caused by the mismatch of the heat expansion coefficients between the oxide layer and SiC, Fe.