Impact of Ionic Liquid Additives and Inorganic Fullerene-Like Tungsten Disulfide on Friction and Wear under Aqueous Environments.

Abstract

Aqueous lubricants are gaining attention due to significant advantages such as being environmentally friendly, tunable, and thermally stable. The oil and gas industry can use such additives to utilize in water-based fluids for applications where small sliding velocities and large lateral forces require enhanced lubrication. This investigation aims to compare the effects of two different additives: (i) inorganic fullerene-like tungsten disulfide (IF-WS2) and (ii) an alkanolamine ionic liquid denoted as AA-IL. Both additives were paired with three different base fluids, deionized water (DIW), aqueous NaCl, and aqueous CaCl2, to measure the impact on fluids commonly utilized in the field. The addition of IF-WS2 to all three solutions resulted in a 30-60% decrease in the coefficient of friction (COF) and wear. Surface analysis by X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS) showed that the formation of a tribofilm (tungsten oxide layer) is primarily responsible for tribological improvements. The AA-IL did not show evidence of any chemical interaction. Instead, a physically bonded film of the AA-IL on the steel surface enabled the improved COF (40-50% reduction) and wear response. Both additives are effective in very small amounts and provide excellent wear and friction reduction properties.