反应烧结碳化硅陶瓷内筒的损毁机制

Damage mechanism of reaction sintering SiC ceramic inner cylinders

以X射线衍射仪、扫描隧道电子显微镜、能量散射光谱仪等手段对在悬浮预热器内筒上使用前后的反应烧结碳化硅陶瓷进行分析,研究该陶瓷应用于悬浮预热器上的损毁机制.碳化硅陶瓷中残存金属硅和表面的碳化硅在高温使用工况下首先氧化成Si O_2,Si O_2在K2O(g)、Na2O(g)、KCl(g)、Na Cl(g)等蒸气以及氯化物作用下黏度降低,形成覆盖于陶瓷表面的氧化层,继而被高速的气固流体冲蚀和磨损掉,并导致新的界面出现.如此循环,使碳化硅陶瓷的外侧逐渐变薄和断裂,直至损毁.提高陶瓷的致密性和降低残余硅含量是改进反应烧结碳化硅陶瓷在悬浮预热器中使用性能的有效途径.

A reaction bonded Si C 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 Si O_2 under the high temperature atmosphere and the liquid viscosity of Si O_2 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 Na Cl（ 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.