激光熔覆镍基合金磨损及电化学腐蚀性能研究

Research on Wear and Electrochemical Corrosion Properties of Laser Cladding Nickel Base Alloy

目的为解决不锈钢零件在工程应用中表层由于磨损、腐蚀导致其使用寿命缩短的问题,修复和提升不锈钢表层的硬度、耐磨性及耐蚀性。方法在总结前期大量实验数据及规律的基础上,采用激光熔覆法在304不锈钢表层制备无裂纹、熔覆质量良好的Ni60涂层。利用光学显微镜、扫描电镜、能谱仪、X射线衍射仪等设备,系统地研究了熔覆层组织的形貌、元素分布及物相结构。采用显微硬度计、摩擦磨损仪、电化学工作站等设备,测试熔覆层的硬度分布、磨损特性及电化学特性。结果涂层具有均匀致密的微观结构,主要以固溶态γ-(Ni,Fe)、碳化物M_(23)C_(6)(M=Fe、Ni、Cr)、硼化物CrB组成,熔覆涂层的显微硬度约为基材的2.5倍,熔覆过程中,硬质增强相的形成是其硬度提升的主要原因。熔覆涂层的磨损率、磨损深度、磨损后表面单位面积的粗糙度(Sa)分别为基材的8.5%、69%、22.2%,与基材相比,涂层的耐磨性能明显更优。涂层的腐蚀速率比基材低2个数量级,涂层表面形成的致密钝化膜是耐蚀性好的主要原因。结论熔覆质量良好的Ni60涂层,较304奥氏体不锈钢基材有更加优异的硬度、耐磨及耐腐蚀性能。

In order to solve the problem that the service life of surface layer of stainless steel parts is shortened due to wear and corrosion in engineering practice,efforts are made to repair and improve the hardness,wear resistance and corrosion resistance of surface layer of stainless steel.On the basis of summarizing a lot of experimental data and rules in the early stage,Ni60 coating with good cladding quality and no cracks was prepared on 304 stainless steel surface by laser cladding.The microstructure,element distribution and phase structure of the cladding surface were systematically studied by optical microscope,scanning electron microscope,energy dispersive spectrometer and X-ray diffractometer.The hardness distribution,wear characteristics and electrochemical characteristics of the cladding surface were measured by microhardness tester,friction and wear tester and electrochemical workstation.The uniform and compact microstructure of the coating is mainly composed of solid solution stateγ-(Ni,Fe),carbides M_(23)C_(6)(M=Fe,Ni,Cr)and boride CrB.The microhardness of the cladding coating is about 2.5 times that of the substrate.The hardness enhancement of the coating is mainly caused by the hard reinforcing phase formed in the cladding process.The wear rate,wear depth and wear surface roughness per unit area(Sa)of the cladding coating are 8.5%,69%and 22.2%of the substrate,respectively.Compared with the substrate,the wear resistance of the cladding coating is obviously better.The corrosion rate of the coating is 2 orders of magnitude lower than that of the substrate,and the formation of dense passivation film on the coating surface is the main reason for the good corrosion resistance.Compared with 304 austenitic stainless steel base material,Ni60 coating with good cladding quality has better hardness,wear resistance and corrosion resistance.