Ionic Liquids as Lubricants of Titanium-Steel Contact

The friction and wear behavior of grade 3 titanium have been studied against AISI 52100 steel at room temperature and at 100 A degrees C, in the presence of six ionic liquid (IL) lubricants, four imidazolium ILs, 1-ethyl-3-methylimidazolium tetrafluoroborate (L102), 1-octyl,-3-methylimidazolium tetrafluoroborate (L108), 1-hexyl, 3-methylimidazolium hexafluorophosphate (L-P106) and 1-benzyl,3-methylimidazolium chloride (ClB), and two quaternary ammonium salts, the chloride derivative AMMOENG (TM) 101 (AM-101) and the dihydrogenphosphate AMMOENG (TM) 112 (AM-112), and compared with that of a mineral base oil. At room temperature, all ILs, except L102, give similar mean friction values, below 0.20, with a 60% reduction with respect to the mineral oil. All ILs, except L102, also reduce titanium wear rates. The poor performance of the short alkyl chain tetrafluoroborate L102 is due to tribocorrosion. The best antiwear performance at room temperature is found for the imidazolium chloride (ClB), although corrosion of the AISI 52100 steel ball is observed. At 100 A degrees C, L-P106 maintains the room temperature friction values and shows a 80% wear rate reduction with respect to room temperature. L-108 fails at 100 A degrees C after a sliding distance of 200 m due to decomposition and tribocorrosion. The friction and wear mechanisms and surface interactions are discussed from friction-sliding distance curves, SEM, EDS and XPS analysis, and XRD data.