A study on the electrocodeposition processes and properties of Ni-SiC nanocomposite coatings

Ni-SiC nanocomposite coatings were prepared on a brass substrate by electrocodeposition. The electrodeposition was carried out by adding the SiC nanoparticles to a nickel-containing bath. Nickel deposition processes were analyzed by cathodic polarization curves, and the plating parameters were determined preliminarily by analyzing the effects of different technological parameters on the deposition process. Then, electrocodeposition processes were carried out with different concentrations of SiC nanoparticles in the bath. The effects of current density, stirring rate, and SiC nanoparticle's concentration in the plating bath on the hardness of coatings were investigated by microhardness tests. Besides the microhardness tests, wearing tests and corrosion tests were also applied to the coatings with the highest hardness and coatings of pure nickel. The structures and surface morphologies of the coatings were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. The experimental results show that the microhardness of the codeposited coating increases with increasing current density and attains a maximum at the SiC concentration of 6 g/L. The decrease in the microhardness at higher SiC concentrations may be due to agglomeration of nanosized particles in the plating bath. Increasing the stirring speed did not give a better quality deposition as coatings produced at low stirring rates always had higher microhardness values than did those at high stirring rates. Furthermore, the Ni-SiC nanocomposite coatings have lower friction coefficient and better corrosion resistance than those of pure nickel coatings.