Effect of Current Type and Density on Tribological Properties of Electrodeposited Ni-Co/MWCNT Nanocomposite Coatings

Nickel (Ni)-cobalt (Co) alloys and multi-walled carbon nanotube (MWCNT)-reinforced Ni-Co nanocomposite coatings were produced by direct current (DC) and pulse reverse current (PRC) electrodeposition methods on a copper substrate with various current densities between 3.0 and 9.0 A/dm2. The effects of current type and density on the microstructural and tribological properties of an unreinforced Ni-Co alloy and MWCNT-reinforced Ni-Co nanocomposite coatings were investigated. The results show that the PRC type increased the hardness value from 261 HV to 290 HV. In MWCNT additions to the Ni-Co nanocomposite coatings, the microhardness values reached 465 HV. Also, MWCNT additions significantly increased the wear resistance and decreased the friction coefficient between the friction surfaces because of the self-lubrication effect of the MWCNT. The PRC type also provided better tribological properties in comparison with the DC type for both samples of unreinforced and MWCNT-reinforced Ni-Co alloys.