40Cr钢表面包埋渗Mo涂层组织及摩擦性能

Microstructure and Tribological Properties of Mo-coating Prepared by Pack-cementation on 40Cr Steel

热扩散渗钼(Mo)是钢材表面化学成分的改性方式之一,其可提高钢的淬透性,与碳作用形成高熔点的碳化物,能够提高钢铁材料表面的耐磨性。为探索热扩散渗钼工艺,分别采用箱式炉加热和感应加热对40Cr钢进行1000~1300℃不同温度下包埋扩散渗处理,利用场发射扫描电子显微镜(FEG-SEM)、X射线衍射技术(XRD)和摩擦磨损试验研究了渗Mo试样的微观组织、元素分布、物相构成以及摩擦磨损性能,并对感应加热渗Mo微观结构的演变机理进行了阐述。结果表明:在1100℃下箱式炉加热未观察到明显的Mo渗层,而感应加热在不同温度下形成了30~70μm厚的Mo渗层;感应加热后试样截面组织由Mo渗层、过渡层、受影响层、基体组成,其中Mo渗层主要由Fe-Mo固溶体(Fe-Mo SS)和碳化物相组成,过渡层由合金珠光体组成,受影响层为贫碳区;研究表明感应加热Mo渗层的最高硬度为560 HV0.2,约为原始试样的两倍,IHM-1200试样的的摩擦因数为0.73,比原始试样低0.12,磨损质量略低于原始试样,Mo渗层显著提高40Cr钢的摩擦性能。

Thermal-diffusion molybdenizing is one of the methods uesd for modifying the chemical composition of steel surface.Mo can improve hardenability of steel,interact with carbon to form carbides with high melting point,and improve the wear resistance of the steel surface.In order to explore the thermal-diffusion molybdenizing process,Mo-coatings are prepared on 40Cr steel by pack-cementation treatment via box-furnace heating and induction heating at 1000-1300℃.Microstructure,element distributions,phases and tribological properties of the treated samples are characterized and studied by the field emission gun scanning electron microscope(FEGSEM),X-ray diffraction(XRD)and friction and wear testing machine.The evolution mechanism of the microstructure of molybdenizing by induction heating is described.The results showed that no obvious Mo-containing layer was observed when heated by the boxfurnace at 1100℃,but a 30-70μm thick Mo-containing layer is formed by induction heating at 1000-1300℃.The cross-sectional structure of the samples after induction heating pack-cementation is composed of Mo-coating,transition layer,affected-layer and substrate.The Mo-coating is mainly composed of Fe-Mo solid solution and Mo containing carbides phase,the transition layer consisted of alloy pearlite,and the affected layer was a carbon-poor zone.Studies show that the highest hardness of the Mo-coating is 560 HV_(0.2),which is about twice that of the untread sample.The friction coefficient of the IHM-1200 sample is 0.73,which is 0.12 lower than the untreated sample.The mass loss is slightly lower than the untreated sample.Friction properties was significantly improved after the formation of the Mo-coating on the 40Cr steel.