钼网表面MoSi_2涂层的制备及其1500℃高温抗氧化性能

Preparation of MoSi_2 Coating on Mo Net and Evaluation of Its Oxidation Behavior at 1 500 ℃

钼网被广泛用作高温催化剂载体,但关于其高温防护涂层的制备及失效机制却鲜有报道。用包埋渗硅方法在钼网表面制备了MoSi_2高温抗氧化涂层,并在静态大气环境中开展了1 500℃恒温氧化试验。利用X射线衍射仪(XRD)、扫描电镜(SEM)、能谱分析(EDS)等对氧化前后涂层的微观形貌和组织结构进行了表征。结果表明:1 500℃氧化2 h,MoSi_2涂层中的Si元素会发生选择性氧化,在涂层表面形成一层连续的、具有"自愈合"功能的熔融态SiO_2保护膜,阻挡氧向基体一侧的扩散,展现出了良好的高温抗氧化性能;高温条件下,涂层中的Si元素会和钼基体发生界面扩散反应生成抗氧化性能差的Mo_5Si_3,同时MoSi_2不断地和氧发生反应生成Mo_5Si_3和SiO_2,当涂层中的MoSi_2完全转化为Mo_5Si_3,涂层将快速氧化失效。

MoSi2 coating with high-temperature antioxidant performance was prepared on Mo net by pack cementation method, and then the coating was evaluated by isothermal oxidation test at 1 500 ℃ in static air. In addition, X-ray diffractometer （XRD） , scanning electron micro- scope （SEM） and energy dispersive spectrometer （EDS） were employed to characterize the micro morphology and phase structure of coating before and after oxidation treatment. Results revealed that after oxidation treatment at 1 500 ℃ for 2 h, the selective oxidation of Si element in MoSi2 coating occurred, and a continuous melt-state Si02 protective film with self-sealing property that could restrain O2 spreading toward the substrate was formed on the surface of coating, which resulted in excellent high- temperature antioxidant performance. Moreover, at high tem- perature, Si element in MoSi2 could spread around the boundary of Mo substrate and form M5Si3 that had bad high-temperature antioxidant per- formance, and meanwhile MoSi2 continuously reacted with oxygen into Mo5Si3 and SiO2. Once the MoSi2 phase of coating was totally consumed, the coating failed quickly by oxidation treatment.