Influence of temperature on tribological behaviour of ionic liquids as lubricants and lubricant additives
Ionic liquids are low-melting-point salts composed entirely of ions, and many of them are liquids at room temperature.
In recent years, studies have indicated that they might be good candidates for lubricants, either in neat or additive form. In this work, a sulfate-based ionic liquid with a pyrollidinium cation was studied as neat lubricant and as additive for glycerol in lubrication of steel–steel contacts. Glycerol was chosen as the base oil because of its high polarity, which allows full miscibility with polar ionic liquids. Tests were performed on an oscillating friction and wear tribometer. The coefficients of friction and wear were measured. The tests were run at room temperature, 50 °C, 100 °C and 150 °C. By using profilometry, optical microscopy, scanning electron microscope and atomic force microscopy (AFM) analyses, it was shown that the ionic liquid plays an important role in the friction and wear reduction, as well as in the smoothening of the worn surface