Ionic liquid-functionalized magnesium silicate hydroxide as an advanced lubricant additive for enhanced tribological performance and micropitting repair

Abstract Rolling contact fatigue (RCF) failures in critical components such as precision gears and high-performance bearings have become increasingly prominent under demanding conditions. Conventional lubricant additives struggle to reduce friction simultaneously, resist wear, and repair dynamic micropitting. To address this challenge, a composite material of ionic liquid-functionalized magnesium silicate hydroxide (MSH) ([DDP][TOA]/MSH (DDP = dialkyl dithiophosphate, TOA = trioctylamine)) was synthesized using hydrothermal synthesis and noncovalent modification. This composite exhibited remarkable dispersion stability and copper corrosion inhibition, as well as superior tribological properties, including friction reduction, wear mitigation, and micropitting repair during rolling–sliding contact. Tribological evaluations revealed that 1.0 wt% [DDP][TOA]/MSH reduced the friction coefficient by 17.2% and the wear volume by 52.5%, demonstrating unprecedented load-bearing capacity and frequency adaptability. Notably, under rolling–sliding contact fatigue conditions, commercial gear oil exacerbated micro-pitting damage continuously, whereas the composite material repaired damage, with a repair efficiency of 72.0%. Surface characterization reveals a three-stage mechanism for the dynamic repair of worn metal surfaces: (1) micro-asperities are removed through mechanical grinding, (2) micro-cracks are filled via tribochemical deposition of FeS/phosphate phases, and (3) a hybrid a-SiC/a-SiOx repair layer is formed with improved mechanical strength, effectively preventing fatigue wear propagation. This work demonstrates the synergistic effect of ionic liquids and layered silicate additives on micropitting repair under rolling contact fatigue, expanding the application of MSH in the field of commercial lubricant additives.