不同(Mo+B)/(Ni+Cr)质量比的原位合成MoB/NiCr涂层的组织结构与性能

Microstructure and Properties of In Situ Synthesized MoB/NiCr Coatings with Different(Mo+B)/(Ni+Cr)Mass Ratios

采用超音速火焰喷涂技术沉积含3种不同(Mo+B)/(Ni+Cr)质量比(1:1,2:1和3:1)的Mo-B-Ni-Cr球磨复合粉末以原位反应制备获得MoB/NiCr涂层。采用扫描电子显微镜(SEM)和X射线衍射仪(XRD)分析了MoB/NiCr涂层的组织结构和物相。同时讨论了不同(Mo+B)/(Ni+Cr)质量比对涂层的组织结构、硬度、结合强度和耐腐蚀性能的影响。研究结果表明,(Mo+B)/(Ni+Cr)质量比为1:1的MoB/NiCr涂层孔隙率最低及涂层厚度最大。在3种涂层中均原位反应生成了Mo_(2)NiB_(2)三元硼化物,且随着(Mo+B)/(Ni+Cr)质量比的增加,涂层中三元硼化物含量随之增加,涂层的硬度值增加,结合强度反而随之降低;由于涂层中三元硼化物的原位生成,MoB/NiCr涂层的硬度值均高于316L不锈钢基体。通过能谱和XRD分析发现,经过360 h熔融锌腐蚀试验后,涂层表层中没有发现锌元素及其金属间化合物,然而随着(Mo+B)/(Ni+Cr)质量比的增加,涂层的孔隙率增加及厚度降低。最后,综合分析可得,相比其他涂层,(Mo+B)/(Ni+Cr)质量比为1:1的MoB/NiCr涂层具有更好的耐熔融锌腐蚀能力。

Three kinds of Mo-B-Ni-Cr ball-milled mixture powders with different(Mo+B)/(Ni+Cr)mass ratios(1:1,2:1,and 3:1)were deposited by the high velocity oxygen-fuel(HVOF)spraying process to in situ synthesize MoB/NiCr coatings.The microstructure and phase composition of MoB/NiCr coatings were analyzed by scanning electron microscope(SEM)and X-ray diffraction(XRD).The effects of different(Mo+B)/(Ni+Cr)mass ratios on the microstructure,microhardness,bonding strength,and corrosion resistance of MoB/NiCr coatings were discussed.The results show that MoB/NiCr coatings with(Mo+B)/(Ni+Cr)mass ratio of 1:1 have the lowest porosity and the largest thickness.Mo_(2)NiB_(2)ternary boride was in situ synthesized in all three kinds of MoB/NiCr coatings.The content of Mo_(2)NiB_(2)ternary boride is increased with increasing the(Mo+B)/(Ni+Cr)mass ratio.The microhardness of MoB/NiCr coatings is increased with increasing the(Mo+B)/(Ni+Cr)mass ratio,while the bonding strength is decreased.After immersion test in molten zinc for 360 h,no zinc or its intermetallic compound can be observed in the surface region of MoB/NiCr coatings according to energy disperse spectrometer(EDS)and XRD analyses.The porosity of the coatings is increased with increasing the(Mo+B)/(Ni+Cr)mass ratio,while the thickness is decreased.Compared with other coatings,the MoB/NiCr coating with(Mo+B)/(Ni+Cr)mass ratio of 1:1 has better corrosion resistance in molten zinc.