Abstract: 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 of β-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.

Key words: sintered SiC, passive oxidation, interface stability, reaction barrier