Preparation and tribological research of the electrodeposited Ni W alloy coatings for piston ring application

This study determines the effect of the electrodeposition process parameters on the composition, mechanical properties and wear resistance of Ni-W alloy coatings. The optimum conditions for the electrodeposition of a Ni-W alloy coating on a piston ring to increase resistance to wear and friction are determined. The results show that the content of tungsten (W) in the Ni-W alloy coatings is between 23.8 wt% and 42.2 wt%, depending on the DC current density and the concentration of the sodium tungstate in the electrolyte. The best mechanical properties are obtained for Ni-40.6 wt% W alloy that is annealed at 600 °C for 1 h. The tribological properties of the coating are determined using a pin-on-disk abrader tester under SAE 10W40 lubricated conditions. The tribological study shows that Ni-40.6 wt%W coating that is annealed at 600 °C for 1 h features a lower coefficient of friction and better anti-wear characteristics than a hard chromium coating that is currently widely used as a coating for piston rings. The resistance of a Ni-40.6 wt%W alloy coating for piston rings to wear and scratching is studied using a 125 cc, single-cylinder, air-cooled engine. The results show that the Ni-40.6 wt%W coating has good resistance to wear and scratching.