Dual-shield teamwork in supramolecular gel: In-situ formed bilayer tribofilm for advanced lubrication

Abstract

Maintaining a sufficiently thick lubricating film under elastohydrodynamic lubrication (EHL) conditions is the core prerequisite for avoiding direct contact between the surfaces of friction pairs. Nevertheless, conventional lubricants generally suffer from slow film formation and insufficient film thickness under EHL conditions. To overcome this limitation, this paper develops a novel supramolecular gel lubricant with outstanding film-forming performance, and molecular dynamics simulations are adopted to elucidate its self-assembly mechanism: intermolecular hydrogen bonds interactions construct a network skeleton that can effectively trap base oil. This gel lubricant exhibits excellent mechanical stability and creep recovery capability, together with high phase transition and thermal decomposition temperatures. Under boundary lubrication conditions, a double-layer tribofilm consisting of iron disulfide, iron oxides and amorphous components forms on the friction surfaces. This tribofilm produces a synergistic protective effect, which drastically reduces friction and wear while improving the load-bearing capacity of the lubrication system. More importantly, the gel lubricant exhibits exceptional film-forming capability under EHL conditions, generating a significantly thicker lubricating film than previously reported lubrication systems. The interconnected three-dimensional network effectively stores the base oil and releases it progressively during operation, allowing the gel lubricant to maintain stable lubrication under varying entrainment speeds. This study provides a molecular-level design strategy for simultaneously enhancing the film-forming capability and comprehensive tribological performance of lubricants.