Study on the layer number effect and synergistic lubrication mechanism in ionic liquid/graphene oxide composite aqueous lubrication system

To address the challenges of high friction coefficient and severe adhesive wear of titanium alloys under aqueous lubrication conditions, this study systematically investigated the layer-number effect of graphene oxide (GO) and its synergistic lubrication mechanism with ionic liquid using macroscopic tribological experiments, SEM, XPS, FIB-HRTEM, and molecular dynamics simulations. Experimental results show that the multi-layer GO/ionic liquid composite system reduces the friction coefficient to 0.0813 and the wear volume by 96.85 % compared to pure water, with a smooth worn surface exhibiting almost no adhesive features. FIB-HRTEM cross-sectional analysis further confirms the formation of a dense tribofilm approximately 15–24 nm thick on the titanium alloy surface. The study reveals that the number of GO layers can significantly affect lubrication performance: even in the absence of ionic liquid, multi-layer GO still significantly outperforms single-layer and few-layer GO; after the introduction of the ionic liquid, its enhanced interfacial adsorption and the improved dispersion of GO synergistically further enhance the lubrication performance. Molecular dynamics simulations reveal that multi-layer GO, through its easier interlayer sliding, denser hydrogen-bonding network, and more stable hydration layer, cooperates with preferentially adsorbed ionic liquid to jointly reduce the interfacial shear strength.