The potential of plasma electrolytic oxidized eutectic aluminium-silicon alloy as a cylinder wall surface for lightweight engine blocks

Abstract

A series of tests was conducted using a reciprocating tribometer to evaluate the tribological performance of a plasma electrolytic oxidation (PEO) treated eutectic aluminium-silicon alloy and was compared with a more conventional nickel-ceramic (Ni-SiC) coating as a reference. The counterpart was a gas-nitrided steel top piston ring and the lubricant was a group III base oil blended with standard detergent and dispersant additives, both with and without dispersions of very fine particles of molybdenum disulphide as a friction modifier. Scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy, and stylus profilometry were employed to characterize the morphology, elemental composition, and surface force analysis of the tribofilm and the wear profile. The tribological performance of the PEO transformed surface was found to be similar to the Ni-SiC coating in the short-duration tribometer experiments undertaken with fully flooded lubrication and at low-speed conditions, with potentially greater durability in the longer term given the properties of the transformed surface layer.