钼合金双层结构MoSi2涂层的制备与组织性能

采用料浆烧结法在TZM钼合金表面制备Mo层，再通过包埋渗法制得双层结构的MoSi₂厚涂层。利用内热法在大气环境下测试了钼合金Si-Mo涂层在1 600 ℃下的高温抗氧化性能。结果表明，涂层由多孔MoSi₂外层和致密MoSi₂内层组成，Mo粉细化对涂层组织致密化和高温抗氧化性能提升有益，平均粒度9.8 μm和2.2 μm的Mo粉制备的涂层在1 600 ℃下的高温抗氧化寿命分别为5.1 h和14.8 h，高温氧化后涂层结构转变为SiO₂氧化层-多孔MoSi₂层-致密层-Mo₅Si₃层。随着氧化持续进行，SiO₂层和Mo₅Si₃层不断增厚，而MoSi₂层持续减薄并转化为Mo₅Si₃，硅元素的持续贫化导致涂层最终失效。

Preparation and Microstructure of Double-Layer MoSi2 Coating on Molybdenum Alloys

A layer of Mo was prepared on the surface of TZM molybdenum alloy by slurry-based sintering method, and then a thick MoSi₂ coating with double-layer structure was prepared by pack cementation method. The oxidation resistance of Si-Mo coating at 1 600 ℃ in atmospheric environment was tested by using internal heating technique. Results show that the coating is composed of an outer layer of porous MoSi2 and an inner layer of compact MoSi₂, and the Mo powder with smaller size is beneficial to the improvement of compaction and high-temperature oxidation resistance of the coating. It is shown that the coating prepared by Mo powder with an average particle size of 9.8 μm and 2.2 μm will fail after oxidation at 1 600 ℃ for 5.1 h and 14.8 h respectively, and the coatings are transformed to have its structure composed of a layer of SiO₂ oxide, a layer of porous MoSi₂, a layer of compact MoSi₂ and a layer of Mo₅Si₃. As the high-temperature oxidation proceeds, the layers of SiO₂ and Mo₅Si₃ will become thicker, while the layer of MoSi₂ will become thinner and transformed into Mo₅Si₃. And a continuous silicon dilution will finally lead to a coating failure.