Ni-Al_(2)O_(3)复合镀层的组织及摩擦性能研究

Microstructure and tribological properties of Ni-Al_(2)O_(3) composite coating deposited by magnetic field pulse electrodeposition

以40Cr钢为基体,用磁场-脉冲电沉积法制得Ni-Al_(2)O_(3)复合镀层。用扫描电镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)和透射电镜(TEM)观察镀层表面形貌和微观结构并分析元素组成,用纳米压痕仪和摩擦磨损试验机对镀层进行纳米压痕硬度和摩擦磨损性能研究。结果表明:无磁场时制得镀层间隙较大、晶粒团簇生长,Al_(2)O_(3)纳米颗粒呈不规则的几何形状散落在镀层中。0.2 A/m时制得镀层形貌光滑平整、组织致密,Al_(2)O_(3)纳米颗粒呈球形紧密吸附在Ni离子周围,此时镀层纳米压痕硬度最高,为6.26 GPa,磨损量最低,为0.3 mg。晶粒生长优选取向为(111)、(220)和(200)平面。磁流体动力学效应可消除自然对流影响,并增强离子传质速率,提高镀层的硬度和耐磨性能。磁化能可加快位错向摩擦表面运动,促进摩擦表面氧化,使磨屑细化和氧化,利于增强摩擦副的摩擦学性能。Ni-Al_(2)O_(3)复合镀层的磨损机理为黏着磨损。

Ni-Al_(2)O_(3)composite coating was successfully prepared by magnetic field pulse electrodeposition on the 40Cr steel base material.The surface topography,micro-structure and element composition of coating were investigated by scanning electron microscope(SEM),energy dispersive spectrometer(EDS)and X-ray diffractometer(XRD)and transmission electron microscopy(TEM).The nano indentation hardness and friction and wear properties of the coating were studied by nano indentation instrument and friction and wear tester.The results show that the gap of coating is large,the grain clusters gron in the form of aggregation,and the Al_(2)O_(3)nanoparticles is scattered in the coating in an irregular geometry when there is no magnetic field.The morphology of coating is smooth and dense and Al_(2)O_(3)nanoparticles are spherical and closely adsorbed around Ni ions when the intensity of magnetic field is 0.2 A/m.Moreover,the hardness of coating is the highest and the wear amount is the lowest,which are 6.26 GPa and 0.3 mg,respectively.The preferred orientation of grain growth are(111),(220)and(200)planes.The magnetohydrodynamics effect can eliminate the influence of natural convection and enhance the ion mass transfer rate,so as to improve the hardness and wear resistance of coating.Magnetization energy can accelerate the movement of dislocations to the friction surface,promote the oxidation of friction surface,refine and oxidize the wear debris,and enhance the tribological properties of friction pair.The wear mechanism of Ni-Al_(2)O_(3)composite coating is adhesive wear.