| This paper using brush plating technology deposited PbSnCu, SnZn and CuSn alloy plating on the surface of 45 steel, which’s brush plating bath is the pyrophosphate system The process conditions, coating microstructure and friction and wear properties were investigated, focused on the study of CuSn alloy coating. By changing the brush plating voltage, pH value, the concentration of main salt in brush plating liquid, plating time and electrode materials of process parameters, to study the influence on the composition and morphology of coating, and the optimum process parameters were determined. The coating of different composition was prepared under the optimum process parameters. Microstructure of films was examined by XRD and SEM. By using energy dispersive X ray fluorescence (EDXRF) measure thickness and composition of coating. Microhardness was tested by micro hardness measurement. The surface friction and wear properties were tested by the comprehensive performance test instrument. The test results show as follows.1.Pb-Sn-Cu three binary alloy With the increasing of SnCl2·2H2O concentrations, tin content in the deposit increased, Pb content decreased, the content of copper is not affected. With the increasing of CuSO4 concentration, Pb content decrease, the content of Cu and Sn increase. With the increasing of plating time, the thickness of plating layer increased and reached the maximum 16.5μm when the value of 36min. The deposition rate of the coating increased at first and then decreased, deposition rate of brush plating 12min reached a maximum value of 0.548 m/min. Phase analysis show that the coating is composed of lead and copper-tin compound. With the increasing of copper content, the compound represented by Cu6Sns become Cu3Sn and hardness increased from HV0.0110.5 to HV0.0119.6. Friction and wear results indicated that the friction coefficient of the coating fluctuate between 0.43-0.56. The wear mechanism is abrasive wear.2. Sn-Zn alloy With brush speed increasing from 65mm/s to 195mm/s, the deposition rate is increased from 0.95μm/min to 1.89μm/min, and amplification is 100%. When the voltage is 2.5, the zinc content is only 0.2%. With the increasing of voltage, the zinc content is up to 63.0%. With ZnSO4·7H2O rising from 23.27g/L to 69.81g/L, zinc content rise from 21.75% to 59.23%. Phase analysis shows that tin and zinc two phase coexistence in the films prepared by 10V. With zinc content increased, hardness increase from HV0.0133.3 to HVo.oi58.6, and amplification is 78%. With zinc content increased, wear resistance increase and friction coefficient increase from 0.22 to 0.30.3. Gu-Sn alloy (1)The optimal process parameters determined through the research were that the value of pH is 9.5, the anode movement speed is 130mm/s, bath temperature of 50℃, the brush plating voltage of 4V. Under this condition, prepare the films which’s tin content from 27.7% to 70.0% by changing the concentrations of SnCl2·2H2O. (2)The phase analysis results show that when the tin content is lower than 38%, the coating is consist of a-Cu solid solution and Cu2oSn6 phase. When the tin content in the range of 38-62.0%, the coating is composed of Cu6Sn5 and Cu2oSn6 and the hardness is higher. When the tin content is 61.4%, the hardness reaches the maximum 329.7HV. When the tin content exceeds 62%, the coating is made up of Cu6Sn5 and 拾-Sn with lower hardness. (3) The performance analysis of the coating showed that the adhesion fluctuate from 18N to 26N. When the plating time is up to 18min, coating porosity is extremely low,0.20-0.63 number/cm2. Under the condition of dry friction, when the tin content is lower than 38%, the friction coefficient of which is between 0.4-0.5. When the tin content is higher than 38%, the friction coefficient of which is between 0.6-0.7, and have better wear resistance. The tin content up to 61.4%, the wear volume is the least, and mainly happen the abrasive wear and adhesive wear. Under the lubrication condition, research the coating which tin content is 61.4% further, the friction coefficient is between 0.05-0.10 and the wear scar width is between 50～60μm, with slight abrasive wear. |
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