钼合金Si-Cr-Ti-SiC-MnO2涂层的制备与组织性能

目的提高钼合金表面红外辐射性能与高温抗氧化性能。方法将40%Si、20%Cr、5%Ti、5%SiC、30%Mn O_2五种粉末与酒精、粘结剂按比例混合,经高能球磨6 h后制得均匀悬浮的料浆。采用浸涂工艺对预处理的钼合金试样进行料浆涂覆,在1450℃真空烧结0.5 h后制得黑色涂层试样。通过1550℃高温静态氧化试验和高温粒子薄片红外光谱综合实验系统,分别评价涂层抗氧化性能和红外辐射性能,并通过扫描电镜(SEM)、能谱分析(EDS)、X射线衍射仪(XRD)对涂层氧化前后的形貌与组织结构进行分析。结果钼合金Si-Cr-Ti-SiC-Mn O_2涂层在700、900℃的法向发射率分别达0.85、0.88,在1550℃高温有氧环境下的静态抗氧化寿命达7 h。原始涂层呈四层复合梯度结构,由外到内分别为SiO_2+Mn3O_4+M5Si3(M指Mo、Cr、Ti)、M5Si3+Mo Si2+SiC+Mn3O_4、Mo Si2、Mo5Si3。高温氧化后,涂层四层复合结构由外到内转变为SiO_2+(Cr,Ti)5Si3+Mn Cr2O_4+Mn3O_4、M5Si3+SiC+Mn Cr2O_4+Mn3O_4、Mo Si2、M5Si3。高温氧化过程中,MSi2高硅化物层逐渐转变为M5Si3低硅化物层,涂层表面形成含Mn Cr2O_4尖晶石相和复合硅化物的致密SiO_2玻璃膜。结论 Si-Cr-Ti-SiC-Mn O_2涂层可有效提高钼合金基体的红外辐射性能和高温抗氧化性能,复合硅化物与硅锰复杂氧化物具有良好的抗氧化性能、高辐射性能和自愈合性能。

Fabrication and Structure Properties of Si-Cr-Ti-SiC-MnO2 Coatings on Molybdenum Alloy

The work aims to improve infrared emissivity property and high temperature oxidation resistance of molybdenum alloy surface. Uniform suspension slurry was obtained after the slurry made of 40wt% Si, 20wt% Cr, 5wt% Ti, 5wt% SiC and 30wt% MnO2powders as well as ethyl alcohol and bonder in proportion were milled with high energy ball for 6 h. Then the slurry was dip coated on the pretreated molybdenum alloy surface. Finally, the silicide coatings were synthesized at 1450 ℃ in vacuum atmosphere for 0.5 h and furnace-cooled down to room temperature. Oxidation resistance and infrared radiation proper-ties of the silicide coatings were evaluated by performing high-temperature static oxidation test 1550℃ and high-temperature particle slice infrared spectroscopy integrated experimental system. Morphology and organizational structure of the unoxidized and oxidized coatings were analyzed by using SEM, EDS, and XRD. Normal infrared emissivity of the Si-Cr-Ti-SiC-MnO2 coating at 700℃ and 900℃ was 0.85 and 0.88, respectively. Static oxidization resistance life at 1550℃ in aerobic environ-ment was 7 h. The original coating exhibited a four-layer composite gradient structure consisting of SiO2+Mn3O4+M5Si3, M5Si3+MoSi2+SiC+Mn3O4, MoSi2layer and Mo5Si3diffusion layer (outside-in). After oxidation at 1550 ℃ for 4 h, composition of the four-layer structure changed into SiO2+(Cr,Ti)5Si3+MnCr2O4+Mn3O4layer, M5Si3+SiC+MnCr2O4+Mn3O4layer, MSi2 layer and M5Si3diffusion layer (outside-in). During the high-temperature oxidation process, the MSi2high silicide layer gradu-ally transformed into M5Si3low silicide layer, and a dense SiO2glass film containing MnCr2O4spinel phase and composite sili-cide took shape on the coatings. The Si-Cr-Ti-SiC-MnO2coating can effectively improve the infrared emissivity performance and high temperature oxidation resistance of the molybdenum alloy substrate. Composite silicide and silicon-manganese com-plex oxide exhibit excellent oxidization resistance, high radiation property and self-healing property.