Preparation of Ni55+FeS composite coatings and their antifriction performances in artificial seawater

Highlights: • FeS film deposited on Ni55 coating by ion sulfurizing is composed with nano-spheres range from 80 nm to 230 nm. • With FeS film lubrication, Ni55 coating showed the lowest friction coefficient under seawater. • Outstanding self-lubrication of FeS film on Ni55 coating could be mainly attributed to closed-packed hexagonal structure. • It also benefits from the good bond strength and the auxiliary lubrication from salts of artificial seawater. The authors recently reported a novel in-situ method of fabricating self-lubricating coatings derived nickel based alloy and ferrous sulfide film by ion sulfurizing at an atmospheric H₂/Ar/H₂S flow. In the present work, thin 3 μm FeS film was deposited on 1.1 mm Ni55 coating with a hardness of about 635 HV. The microstructural evolution, the bond strength with substrate and antifriction properties in artificial seawater of the processed film are reported. The surface roughness value of FeS film is 0.08 μm. The diameters of FeS nano-spheres in the film are in the range of 80–230 nm. FeS self-lubricating film exhibited the best self-lubricating effect on Ni55 coating in artificial seawater, compared with that in dry friction and deionized water. This was attributed to its close-packed hexagonal structure, the separation of the salts, and the auxiliary lubrication and cool effect of artificial seawater.