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通过热重分析法研究了WSi2 /MoSi2 复合材料在 4 0 0～ 70 0℃的氧化性能 ,采用X 射线和SEM分析了表面氧化相的组成和表面形貌。结果表明 :WSi2 /MoSi2 复合材料具有较低的低温抗氧化性 ,5 0 0～ 70 0℃氧化会发生“PEST”现象 ;6 0 0和 70 0℃氧化时的质量增重与时间近似于线性关系 ;大量MoO3 和WO3 等挥发性氧化相的形成 ,破坏了连续致密保护性SiO2 膜的形成 ,促进了裂纹的产生与扩展 ,导致颗粒分离 ,成为“PEST”现象发生的主要原因
The oxidation properties of WSi2 / MoSi2 composites at 400 ~ 700 ℃ have been studied by thermogravimetric analysis. The composition and surface morphology of the surface oxidized phases have been analyzed by X-ray and SEM. The results show that: the WSi2 / MoSi2 composites have low low temperature oxidation resistance, “PEST” phenomenon occurs at the temperature of 500 ℃ ~ 700 ℃; the weight gain and time of the oxidation at 600 ℃ and 70 ℃ are approximately linear The formation of a large number of volatile oxidized phases, such as MoO3 and WO3, undermined the formation of continuous and dense protective SiO2 films, promoted the generation and propagation of cracks and led to the separation of particles, which became the main reason for the “PEST” phenomenon