Friction and wear behaviour of fully formulated water-based lubricants under rolling/sliding contacts

This study evaluates the tribological performance of fully formulated water-based lubricants (WBLs) under rolling/sliding conditions. The WBLs are composed of water-soluble glycols and glycerol with a functional proportion of water. They exhibited significantly lower friction across all lubrication regimes, with near superlubricity achieved under certain conditions. Unlike conventional oils, WBLs showed minimal shear heating effects and exhibited a low shear response with increasing slide-to-roll ratios. Long-duration tests confirmed consistently lower friction for the WBLs. Post-test analysis showed comparable wear between selected WBLs and the reference oil at 40 °C but greater surface modification for WBLs at higher temperatures. Observed wear mechanisms included abrasive and adhesive wear, with occasional instances of spalling after prolonged tests. X-ray photoelectron spectroscopy (XPS) analysis suggested the presence of chemical species on wear scars, attributed to additive-surface interactions. These findings highlight the potential of fully formulated WBLs in rolling/sliding contacts and their current state in comparison to a conventional gear oil. • Water-based lubricants (WBLs) showed significantly reduced friction, approaching superlubricity under engineering surface and specific operating conditions. • Tribotesting shows friction stability and tribofilm formation for certain WBL formulation. • Steel surfaces tested under WBLs shows wear as failure mode. spalling was observed for glycol-water solution. • Trace of chemical species found on wear track, potentially originated from surface-additive interaction.