A reaction bonded SiC ceramic used in a suspension preheater inner cylinder was comparatively analyzed before and after use by X-ray diffractometer,scanning tunneling microscopy and energy dispersive spectroscopy,and its damage mechanism was studied. The results show that residual silicon metal in the Si C ceramic and silicon carbide in the surface are firstly oxidized into SiO2 under the high temperature atmosphere and the liquid viscosity of SiO2 decreases,resulting in the formation of an oxidation layer because of the existence of an alkaline steam of K2O(g),Na2O(g),KCl(g) and NaCl(g) and chlorides. Afterwards the oxidation layer is scoured and frayed by high-speed air flow,leading to a new interface. With the cycle repeating,the outside of the Si C ceramic becomes to be thinner little by little and appears to rupture till damage. As a result,the promotion of densification and the reduction of residual silicon metal are effective ways to improve the use ability of the reaction bonded Si C ceramic in a suspension preheater.
