交直流叠加电镀Ni-Fe-W层性能及其工艺参数优选

Properties of Ni-Fe-W Coating Electrodeposited by Superimposed Alternating Current/Direct Current Electroplating and Optimization of Process

为了提高电镀层的表面性能,运用交直流叠加技术在铜基体上电镀Ni-Fe-W合金层。由IM6e电化学工作站提供交直流叠加电流,研究频率、振幅、温度、电流密度等因素对镀层的影响,并优选出了最佳值;通过X射线衍射、SEM对镀层进行表征,用Tafel极化曲线和交流阻抗分析并比较了交直流叠加电镀层和直流电镀层的耐腐蚀行为。获得的最佳工艺参数:25 g/L NiSO4.7H2O,10 g/L FeSO4.7H2O,45 g/L Na2WO4.2H2O;电流密度5 A/dm2,叠加的交流电振幅20 mV,频率800 Hz,温度60℃,施镀时间1 h。结果表明:交直流叠加电镀工艺获得的镀层表面光滑、平整,硬度和耐蚀性能等明显优于直流电镀层;镀层中钨含量的变化决定了镀层的晶型在晶态和非晶态之间转换。

Electroplated Ni-Fe-W alloy coating was prepared on the surface of Cu substrate by superimposed alternating current/direct current(AC/DC) technology.Thus an IM6e electrochemical workstation was performed to generate AC/DC power.The effects of frequency,amplitude,temperature and current density on the properties of the alloy coating were investigated,and the optimized electroplating condition was established.Besides,the phase composition and microstructure of the alloy coating were analyzed by means of X-ray diffraction and scanning electron microscopy.The corrosion resistance of the alloy coating was evaluated and compared with that of direct current electrodeposited coating,based on measurement of Tafel polarization curves and electrochemical impedance spectra.As the results,the optimized composition of the electroplating bath was determined as 25 g/L NiSO4·7H2O,10 g/L FeSO4·7H2O and 45 g/L Na2WO4·2H2O,while the optimized electroplating parameters were determined as current density of 5 A/dm2,potential of 20 mV,alternating current frequency of 800 Hz,temperature of 60 ℃ and plating time of 1 h.Resultant Ni-Fe-W alloy coating was fine and smooth,and possessed much higher hardness and better corrosion resistance than DC electrodeposited coating.The crystal-amorphous transformation of the alloy coating was dominated by varied content of W.