电泳-电沉积Ni-Al_2O_3纳米复合层的微观结构及性能

Microstructure and Performance of Ni-Al_2O_3 Nano-Composite Coatings Prepared by Electrophoretic- Electrodeposition

为了改善纳米复合镀层的物理、力学性能,以电泳-电沉积工艺制备了具有较高纳米Al2O3含量的Ni-Al2O3纳米复合镀层。用SEM、TEM、显微硬度计等对复合镀层的表面微观形貌、显微硬度以及耐磨性能进行了分析;探讨了电泳液中α-Al2O3微粒浓度、电沉积电流密度对复合镀层表面微观形貌、显微硬度及其与基体的结合力的影响。结果表明:α-Al2O3纳米粒子弥散分布于镀层之中,并对基质金属晶粒产生细化作用;电泳液中α-Al2O3微粒浓度对复合镀层表面微观形貌影响较大,电沉积电流密度对微观形貌无明显影响;随着电泳液微粒浓度和电沉积电流密度的增大,复合镀层显微硬度均呈下降趋势,在电泳液微粒浓度8 g/L,电沉积电流密度0.5A/dm2时,复合镀层具有最大显微硬度442 HV,较纯镍镀层有明显提高。镀层中微粒体积分数约为30%时,镀层的耐磨性能及与基体的结合性能最为优异。

Ni- Al_2O_3composite coatings with high percentage of Al_2O_3 nano- particles were prepared by electrophoretic- electrodeposition technique.The surface morphology,microhardness and wear resistance of the composite coatings were characterized by scanning electron microscopy,transmission electron microscopy and microhardness instrument.Moreover,the influence of electrophoretic concentration and electrodeposition current density on the morphology,microhardness and adhesive strength of the composite coatings was discussed.Results showed that the α- Al_2O_3 particles were well dispersed in the coatings and refined the matrix metal grains.Particle concentration of α-Al_2O_3 in electrophoretic bath affected the surface morphology remarkably while electrodeposition current density did not affect the morphology apparently.Additionally,the microhardness of the composite coating decreased with the increase of Al_2O_3 particle concentration and electrodeposition current density.When the particle concentration was 8 g/L and the electrodeposition current density was 0.5 A/dm^2,the microhardness of coating was 442 HV,which was much higher than that of pure Ni coating.Besides,the most excellent wear resistance and adhesive strength were achieved when the volume fraction of the particle was about 30%.