| Wear and tear of machines is a process of the wastage of surface layer materials because of rubbing unceasingly when the mutual contact objects move relatively. Countries around the world cost a lot each year for the replacement due to wear and tear parts of machines. It is an effective way to improve wear resistance of machines by preparing wear resistance and self-lubrication composite plating by electroplating.In this paper, Ni-TiB2 composite plating and Ni-TiB2-La2O3 composite plating were prepared by electroplating. The effect of different kinds of surfactants and concentration, concentration of TiB2 and La2O3 particles, current density, pH value, stir speed and temperature of plating bath on microhardness and wear mass of composite plating was studied, and the optimal operating conditions were found. The composite plating composition, structure, surface and wear track morphology were analyzed by inductively coupled plasma atomic emission spectrometer (ICP-OES), X-ray diffraction (XRD) and scanning electron microscopy (SEM).The corrosion resistance of different platings were investigated by CHI660C electrochemical station. From the research, the conclusions were as follow:1. The optimal operating conditions is as follows:TiB2 concentration 15g/L～20g/L, La2O3 concentration 2g/L～3g/L, current density 3.5～4.5A/dm2, pH value 4.5～5.5, surfactant concentration 0.075～0.1g/L, stir speed 200-300rpm, temperature of plating bath 45～55℃。2. The result of ICP-OES inspection showed that the quality percentages of La and Ti elements in Ni-TiB2-La203 composite plating were 0.15% and 2.97%, and converting into quality percentage of La2O3 and TiB2 were 0.18% and 4.31%.The result of XRD indicated that the 20 diffraction angle of TiB2 were in 27.637°、34.160°nd 44.437°,and the 2θdiffraction angle of Ni were in 44.560°、51.841°nd 92.921°.Because the quality percentage of La2O3 in Ni-TiB2-La203 composite plating was low and its 20 diffraction angle overlapped with that of TiB2, the 20 diffraction angle of La2O3 was not obvious. The result of SEM showed that the pure Ni plating was uniform, regular and there were TiB2 particles in composite platings. Wear track morphology showed that there were obvious furrow, nick and flake evidence in pure Ni plating, whereas there was less above evidence in composite plarings.3. At the optimal operating conditions, the microhardness, wear resistance and corrosion resistance of Ni-TiB2 and Ni-TiB2-La2O3 composite plating were better than the pure Ni plating.(1) The microhardness of Ni-TiB2 composite plating is 620.1HV improving about 18.6% compared with that of pure Ni plating about 522.8HV and Ni-TiB2-La203 composite plating is 646.0HV improving about 23.6% compared with that of pure Ni plating.(2) At the testing condition, the wear mass of pure Ni plating,Ni-TiB2 composite plating and Ni-TiB2-La2O3 composite plating were 0.43mg,0.21mg and 0.10mg.The wear resistance of composite plating is improved 1 times and 3 times respectively. The friction coefficient of pure Ni plating, Ni-TiB2 composite plating and Ni-TiB2-La2O3 composite plating are 0.640,0.885 and 0.670.(3) At the testing condition, the corrosion potential of pure Ni plating, Ni-TiB2 composite plating and Ni-TiB2-La2O3 composite plating were-272mV,-246mV and-252mV and their corrosion current densities respectively were 4.092μA/cm2, 1.123μA/cm2 and 0.133μA/cm2. Composite platings had more positive potential and smaller corrosion current density than that of pure Ni plating which showed that the corrosion resistance of composite platings was better than that of pure Ni plating.4. Current density and pH value had a distinct effect on co-deposition speed of composite plating. The co-deposition speed was increscent with improving the current density. When current density was 4.5A/dm2, the co-deposition speed was 43.1μm/h which was improved 339.8% compared with that of 1.5 A/dm2.However, when the current density was higher, there was burn evidence occurring. The co-deposition speed was increscent with improving pH value. When pH value was 3.0, the co-deposition speed was 29.2μm/h.However, when pH value between 4.0 and 6.0, the co-deposition speed had a little change.At present, there hasn’t been a report about technology and performances of Ni-TiB2-La2O3 composite plating by electrodeposition, and this is the innovation of this paper. |
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