Effects of pulse plating parameters on the microstructure and properties of high frequency pulse electrodeposited Ni-Co/ZrO_2 nanocomposite coatings

摘要

Ni-Co/ZrO_2 nanocomposite coatings were fabricated in a modified Watt's bath by using high frequency pulse electrodeposition and the effects of pulse parameters such as frequency and duty cycle on the microstructure and properties were investigated. The surface morphology, phase structure, and microhardness of the Ni-Co/ZrO_2 nanocomposite coatings were characterized by scanning electron microscopy with energy dispersive spectroscopy, X-ray diffraction and Vickers' microhardness tester. The corrosion behaviour of the nanocomposites was evaluated by electrochemical impedance spectroscopy in the 3.5 wt% NaCl solution. The results revealed that increasing frequency and duty cycle resulted in a change of morphology from rough and porous structure to compact and homogeneous structure and reduced the ratio of relative intensity I(200)/I(111) of the Ni-Co/ZrO_2 nanocomposites by intervening the adsorption-desorption of interfacial inhibitors at the cathode/solution interface. Furthermore, the effects of frequency and duty cycle on the microhardness of Ni-Co/ ZrO_2 nanocomposites should be associated with the ZrO_2 nanoparticles according to dispersion strengthening from Orowan mechanism. It has been found that the corrosion resistance of the nanocomposites in 3.5 wt% NaCl solution depended on the incorporation of ZrO_2 nanoparticles and the phase structure of Ni-Co/ZrO_2 nanocomposites.