采用超声辅助电镀法在Q235钢基体表面上制备了纳米叠层Ni镀膜.利用X射线衍射分析测定了镀膜的相结构和晶粒尺寸,在扫描电镜下观察了镀膜试样的剖面微观形貌,通过在室温7%HCl溶液中的浸泡实验考察了镀膜试样的耐腐蚀性能,采取磨轮磨损实验法对镀膜的耐磨性能进行了评价. 结果显示,纳米叠层Ni镀膜沿着最密排的(111)晶面择优取向生长, 其微结构明显呈平整层状重复堆积结构,普通电镀Ni镀膜的柱状晶垂直外延生长现象已被彻底消除. 与普通电镀Ni镀膜相比,纳米叠层Ni镀膜的耐磨性能不仅明显改善, 而且其耐腐蚀性能得到显著提高.

Nanosized multilayered Ni coatings were deposited on Q235 steel substrates by ultrasound-assisted electrodeposition. The multilayered Ni coating has a laminated structure of ordinary Ni layer/ultrasonic Ni layer. In order to determine the corrosion and wear property of this novel multilayered Ni coating, conventional Ni coating and bilayered Ni coating were prepared. The phase structure and average grain size of the Ni coatings were determined by X—ray diffraction analysis. Cross section morphologies were observed by scanning electron microscope. Corrosion properties of the Ni coatings were investigated by the immersion test in 7%HCl solution at room temperature, and then their corrosion morphologies were examined by scanning electron microscope. Another way to evaluate the corrosion resistance of the Ni coatings is to calculate the porosity of the Ni coatings using porosity analysis software on an optical microscope. Wear resistance of the Ni coatings were evaluated by rubber wheel test method. The test condition was 400^# SiC emery paper and the applied load on the samples is 6.3 N. Moreover, after 1500 cycles, cross sections of the worn Ni coating samples along the wear direction were observed by means of scanning electron microscope. The results indicate that the growth orientation of the multilayered Ni coating is (111) preferably. Its microstructure is obviously a smooth stacker--up laminated structure. Hence, the epitaxial columnar growth of the conventional Ni coating is annihilated by the formation of the multilayered structure. Compared with the conventional Ni coating, not only the wear resistance of the multilayered Ni coating is improved obviously, but also the corrosion resistance of the multilayered Ni coating is enhanced dramatically. With multilayered structure, the pinholes were obviously inhibited. That is because the multilayered Ni coating can cover the whole surface of the substrate without pinhole interruption. The multilayered structure can extend the pinhole passages extremely for the multilayered Ni coating, unlike the direct and straight pinhole passages for the conventional Ni coating. Therefore, its corrosion mechanism is the uniform corrosion, instead of the hydrogen blistering and Fe/Ni galvanic couples for the ordinary Ni coating. The wear mechanism of the multilayered Ni coating is the adhesive wear, which is a kind of the so-calledmicro-area detachment; while that of the ordinary Ni coating consists of adhesive wear, which can lead to the wear behavior of the bulk damage due to the columnar microstructure.