pH-dependent lubrication mechanism of graphene oxide aqueous lubricants on the strip surface during cold rolling

The tribological performance and lubrication mechanism of graphene oxide (GO) aqueous lubricants with different pH levels on the strip surfaces during cold rolling were investigated. And triethanolamine (TEA) was used to adjust the pH levels of GO lubricants. The morphology of GO and physical characterization of GO lubricants were carried out. Four-ball tribological tests and cold rolling experiments were conducted to obtain the tribological behaviors of GO lubricants on the strip surfaces. To figure out the lubrication mechanism, the surfaces of the rolled strips using GO lubricants were analyzed utilizing a series of experiments. The increase in the pH value of lubricants changed the intrinsic structure of GO, resulting in better dispersibility and wettability. The change of physical characteristics significantly improved the antifriction and antiwear properties of lubricants, and the alkaline lubricant (pH 9.0) exhibited the best lubrication performance. A diameter-height ratio (lambda(d)) applied by a calculation method was proposed to approximatively ascertain the lubrication regime during the cold rolling. The lambda(d) and the surface quality of the rolled strips indicated that the lubrication regime was the boundary lubrication when using the alkaline lubricant. Moreover, GO particles in the alkaline lubricant could repair the strip surface by mending effect and form the physically adsorbed layers. The layers prevented direct contact between rolled surfaces, further amending the surface quality of the rolled strips.

Automated summary

The study investigated the tribological performance and lubrication mechanism of graphene oxide aqueous lubricants with different pH levels on strip surfaces during cold rolling. The results showed that the alkaline lubricant (pH 9.0) exhibited the best lubrication performance, and increasing the pH value of the lubricant improved its anti-friction and anti-wear properties.