Tribocorrosion study of electrodeposited Ni W alloy/BN(h) composited coatings for piston rings

This study determines the effect of the mechanical properties and tribocorrosion characteristics of a Ni-W alloy and Ni-W-BN(h) composite coating on Fe substrate. The effect of coating a piston ring on engine performance is also determined. The experimental results show that the structure of Ni-W alloy and Ni-W-BN(h) coatings that are deposited by direct current electrodeposition features no defects, such as cracks. The BN(h) content of the composite coating is about 5.1 vol%. Ni-W alloy and the Ni-W-BN(h) composite coatings are annealed at 600 °C for 1 h. The respective hardness values are 1049 and 989 HV. The tribocorrosion experiment uses a ball-on-disk abrasion tester and a potentiostat with a 3.5 wt% NaCl solution at room temperature. The results show that a Ni-W-BN(h) composite coating that is annealed at 600 °C for 1 h and is subject to a load of 15 N and + 600 mV has the lowest average corrosion current of 0.05A and the lowest wear loss. The coating is applied to a piston ring and run in a 125 cc single-cylinder air-cooled engine. The brake mean effective pressure (Bmep) and fuel conversion efficiency (ηf) for piston rings that are coated with annealed Ni-W alloy and Ni-W-BN(h) composite coating is significantly increased. The wear pattern for the piston ring shows that the annealed Ni-W-BN(h) composite coating is very resistant to wear.