Synergistic Tribofilm Growth in Ethylene Glycol: A Dual-Additive Approach for Superior Lubrication

This study provides an original insight into the synergistic mechanism through which TM-104 and Vanlube 672 facilitate the in situ formation of a nanoscale bilayer tribofilm in ethylene glycol-based hydraulic fluid. By optimizing the additive formulation to 0.5 wt.% TM-104 and 2.0 wt.% Vanlube 672, a structurally graded tribofilm was autonomously assembled at the friction interface, comprising a 6 nm-thick P_xO_y-rich inner layer and a 140 nm-thick amorphous carbon outer layer. This engineered interlayer delivers exceptional tribological enhancements, with a 31% improvement in lubricity, a 71% increase in wear resistance, and a remarkable 577% enhancement in extreme-pressure load capacity. The first discovery was that there were differences in the mechanisms between these two layers: the inner P_xO_y layer establishes strong chemisorption bonds with the substrate, while the outer carbon layer facilitates energy dissipation through shear-induced graphitization. These findings establish a new paradigm for designing multi-functional lubricant additives and provide a scientific basis for developing high-performance fire-resistant hydraulic fluids operable under extreme conditions.