Xinfu Liu, Ningbo Liu, Qinglun Che, Yi Li, Litian Hu, Chunhua Liu, Songwei Zhang
Versatile ionic liquid (IL) additives could significantly improve the service performance of greases under complex working conditions. This study investigates the influence of two nitrogen-containing heterocyclic ILs (1-butyl-3-methylimidazole 4,6-dimethyl-2-mercaptopyrimidine [BMIM][DMMP] and 1-butyl-3-methylimidazole 2-mercaptobenzothiazolate [BMIM][MBT]) as additives on the performance of titanium complex grease (TCG). Rheological and tribological analyses demonstrate that [BMIM][DMMP] significantly enhances the oil control capability and thickener network entanglement. Both additives improve antiwear and friction reduction properties. Specifically, the lone pair electrons on the pyrimidine nitrogen in [BMIM][DMMP] facilitate coordination with metal surfaces, while its sulfur-containing active group generates stable sulfate-rich lubricating films during friction, leading to superior lubrication. This work provides a theoretical basis for designing high-performance grease additives through IL structural modification.