Influence of Dispersion Methods on Nano-Al2O3/Ni+Co Composite Coating by Electrodeposition

The metal and nano-ceramic nanocomposite coatings were prepared on gray cast iron surface by electrodepositon. The nickel and cobalt were used as metal matrix of coating, and the nano-Al2O3 was chosen as second-phase particulates, which had good chemical stability, high microhardness and good wear resistance. The morphology of composite coatings was flatter and microstructure was denser than pure nickel and cobalt coatings. The composite coatings were fabricated by different dispersion methods such as high speed mechanical stir, ultrasonic vibration and ultrasonic vibration together with mechanical stir. The result indicated the nano-Al2O3/Ni+Co composite coating with fine and compact microstructure are obtained compared with pure Ni-Co coating. The nanoparticles were dispersion evenly when dispersion style was ultrasonic vibration together with mechanical stir according to composite coatings SEM images of different dispersion style. The concentration of nanoparticulates reached a maximum value when the dispersion style was ultrasonic vibration together with mechanical stir, at the same time the mechanical property such as microhardness reached a maximum value also. The reason was that nano-Al2O3 caused dispersive strengthening and grain refining.