The effect of direct and pulse current on the Ni-WC nanocomposite coatings and evaluating its wear behaviour

In this work, Ni composites incorporated with WC particles of nano-sized were electrodeposited from nickel Watts type bath under both pulse and direct current conditions. The effects of pulse and direct current on the surface morphology, grain size, preferred orientation of the deposits, microhardness and the amount of embedded nano-WC particles in the coatings were investigated. The results represented that nanocomposite electrodeposits prepared under pulse plating conditions exhibited higher incorporation percentages and better distribution of WC particles than those obtained under direct plating conditions, especially at low duty cycles. Scanning electron microscope, energy dispersive Xray analysis and X-ray diffraction studies were used to characterize the coatings. A change in surface morphology, texture and WC incorporation was observed with changing the current type. Pin-on-disc tribo tester was employed to study the wear and friction behaviour of the Ni–WC nanocomposite coatings. Results show that Ni–WC nanocomposite coatings have lower friction coefficient against steel counter body as compared with that of the nickel–steel pair. The microhardness and wear resistance of the coatings also increased with increasing content of the WC nano-particles in coatings. Friction and wear mechanisms operative in Ni–WC nanocomposite coatings against steel are discussed.

Keywords:

Nanocomposite coatings , tungsten carbide , electro-co deposition , nano-reinforcement , wear