磷化电流密度对A286合金电化学磷化膜组织结构和结合强度的影响

Effect of Phosphating Current Density on Microstructure and Adhesion Strength of Electrochemical Phosphating Film on A286 Alloy

A286合金表面易钝化,通过传统化学磷化方法在其表面难以沉积磷化膜,而电化学磷化可避免钝化膜对磷化反应的抑制作用。因此,研究磷化电流密度对磷化膜组织结构和性能的影响规律很有必要。通过电化学磷化首次在A286合金表面形成了致密、高膜基结合力的磷化膜。利用电化学工作站对不同电流密度下磷化过程中电位-时间(ϕ-t)曲线进行测绘,研究电化学磷化膜生长过程的特点;使用扫描电子显微镜(SEM)观察磷化膜的显微组织形貌;使用能谱仪(EDS)分析磷化膜中不同区域的化学成分;使用X射线衍射仪(XRD)研究磷化膜的物相结构;使用划痕仪测定磷化膜与基体的结合力。结果显示:A286合金电化学磷化膜的沉积模式为逐层生长-堆叠的形式。低电流密度下,磷化膜为单一的Hopeite相,组织结构粗大、疏松,膜基结合力约为6 N。随着磷化电流密度的增加,磷化膜逐渐转变为Zn+Hopeite复相,组织结构细化、致密,膜基结合力提高。当阴极电流密度为160 mA/cm^(2)时,膜基结合力高于60 N。综合可知,磷化电流密度的增加有利于电化学磷化膜的致密化,有利于膜基结合力和耐磨性的提高。

The surface of A286 alloy easily undergoes passivation,making it difficult to deposit a phosphating film on surface of A286 alloy using the traditional chemical phosphating method.However,electrochemical phosphating can avoid the inhibitory effect of the passivation film on the phosphating reaction.Therefore,studying the influence of phosphating current density on the microstructure and properties of the phos-phating film is necessary.In this study,a compact phosphating film with high film-base adhesion strength was formed on the surface of A286 alloy using electrochemical phosphating for the first time.The potential-time(ϕ-t)curves of the phosphating process under various current densities were mapped using an electrochemical workstation to examine the characteristics of the growth process of electrochemical phosphating films.The microstructure and morphology of the phosphating film were observed using a scanning electron microscope(SEM).Using an energy dispersive spectrometer(EDS)to analyze the chemical composition of different areas of the phosphating film.X-ray diffraction(XRD)was employed to study the phase structure of the phosphating film,and the adhesion strength between the phosphating film and substrate was meas-ured using a scratch tester.Results showed that the deposition mode of the electrochemical phosphating film on A286 alloy occurred through lay-er-by-layer growth stacking.At low current densities,the phosphating film was formed as a single Hopeite phase with a coarse and loose struc-ture,and the bonding force between the film and the substrate was about 6 N.As the phosphating current density was increased,the phospha-ting film gradually transformed into a Zn+Hopeite multiphase,resulting in a refined and dense microstructure,and the adhesion strength be-tween the film and substrate was improved.At a cathode current density of 160 mA/cm^(2),the bonding force between the membrane and sub-strate exceeded 60 N.Generally,the increase in phosphating current density was found to be beneficial for the densification of the electrochemical phosphating film and enhanced both the adhesion strength between the film and substrate and wear resistance of the film.