The tribological properties of the polyurea greases based on oil‐miscible phosphonium‐based ionic liquids

Abstract Oil‐miscible phosphonium‐based ionic liquids have recently been attracted much attention. This study is to develop potentional high temperature lubricating greases based on oil‐miscible phosphonium‐based ionic liquids. This lubricating grease is prepared using oil‐IL blend, which was obtained by adding 10wt% oil‐miscible phosphonium‐based ionic liquids into the PAO 40 base oil as base stock. Compared with the traditional PAO 40 polyurea grease, this polyurea grease has a little lower dropping point. Corrosion test results show the polyurea grease that was prepared using phosphonium‐based ionic liquids cations connected with longer alkyl chains that are no corrosion to brass and steel. Most importantly, the polyurea greases demonstrate very promising tribological properties at 150°C, such as low friction coefficient, small wear volume, and high lubrication failure load. Surface characterization revealed the tribochemical film containing iron oxide, and Fe[PO 4 ] was formed on the worn surface.