Effect of PC electrodeposition on the structure and tribological behavior of Ni-Al2O3 nanocomposite coatings

In this study, Ni-Al2O3 metal matrix composite (MMC) coatings were prepared from a modified Watt's type electrolyte by pulse current (PC) plating under current densities varying between 1 and 9 A/dm(2). The tribological tests were performed with a reciprocating ball-on-disk apparatus sliding against a M50 steel ball (empty set 10 mm). The wear tests were carried out at sliding velocities of 50, 100 and 150 mm/s under a constant load. The results compared with our previously published work of DC electrodeposited coatings. The results showed that the electrodeposition method can significantly affect the microstructure and tribological behavior of Ni-Al2O3 nanocomposite coatings. For the same current density, PC electrodeposition creates coatings with higher co-deposited particle content more homogenous particle distribution, higher wear resistance at high sliding distance and improved friction coefficients. The superior dispersion of Al2O3 nanoparticles in PC-coated materials contributed to its increased load bearing capacity. Detailed tribological tests and characterization showed that DC- and PC-coated nanocomposite layers yielded different wear mechanisms depending on the sliding velocity. (C) 2014 Elsevier B.V. All rights reserved.