反应结合SiC电热材料的高温氧化特征

OXIDATION CHARACTERISTICS OF REACTION-BONDED SILICON CARBIDE ELECTROHEATING MATERIAL AT HIGH TEMPERATURE

研究了反应结合SiC电热材料在 110 0～ 15 80℃空气介质中加热时的氧化特征。结果表明 :加热温度高于 14 2 0℃后 ,材料基体中的残留Si熔化并流动到表面形成SiO2 。氧化后形成的SiO2 与表面氧化层融为一体 ,提高了表面氧化层的致密度 ,有利于材料的抗氧化性能。15 0 0℃左右为材料的抗氧化性能转折温度。在 15 0 0℃以下氧化时 ,反应结合SiC的抗氧化行为与重结晶SiC接近 ;高于 15 0 0℃氧化时 ,材料表面发生破坏性氧化 ,引起电热材料的失效。 15 0 0℃氧化后的表面氧化层中同时存在低温石英、方石英和非晶态SiO2 。

The oxidation characteristics of reaction-bonded silicon carbide electroheating material were studied at 1100°C-1580°C in air. The result indicates that when the heating temperature is over 1420°C, the remnant Si in substrate melts and flows to the surface to form the silica. The combination of silica and the surface oxide layer enhances the compactness of the surface oxide layer, which is favorable for improving the characteristic of oxidation resistance of the material. The transition temperature of oxidation resistance is about 1500°C. The oxidation resistance of reaction-bonded SiC approaches to that of recrystallized SiC when the oxidation temperature is less than 1500°C, and if it is over 1500°C, the ruinous oxidation occurs on the material surface, which causes the invalidation for the electroheating material. There are low temperature quartz, cristobalite and amorphous silica in the surface oxidation layer after the oxidation at 1500°C.