Tribological behavior of nanodiamond-dispersed lubricants on carbon steels and aluminum alloy

This paper examined the rheological property of nanodiamond-dispersed oil lubricants and their tribological performance with two carbon steels and an aluminum alloy. A commercial lubricant and a base oil with the same viscosity were used as the base stocks. These two oils, with different nanodiamond concentrations, were studied. The superior dispersive performance of the base oil was depicted from its higher zeta potential. The antiwear and friction-reduction capabilities of the various dispersions were explored by conducting a series of tribological pin-on-disk tests. The pin was made of carbon chromium steel. The rotating disks were made of AISI 1045 steel, AISI 1025 steel and 6061-T6 aluminum alloy. Surface topographies of the disks’ wear tracks, friction coefficient, and microhardness of contact surface were compared. The results show that nanodiamond-dispersed lubricants are capable of reducing these three metals’ wear loss. However, the wear mechanisms are different. The dispersions’ antiwear capability for the carbon steels is improved by a mechanism which was characterized not only by the viscosity of the nanodiamond suspensions but also by the promotion of contact surfaceʹs toughness due to the embedded nanodiamonds from the lubricant. On the other hand, the wear mechanism of the aluminum alloy is mainly dominated by the viscosity of the nanodiamond suspensions.