Effect of ionic liquid as additive on the tribological performance of potassium stearate films

Potassium stearate films doped with ionic liquid were prepared by dip-coating on hydroxyl silicon substrates. The tribological property of the composite films sliding against AISI-52100 steel ball was investigated with dynamic static friction coefficient measurement apparatus in ball-on-plate configuration. The morphologies of the wear tracks of the various films and the counterparts were examined using a scanning electron microscope equipped with an energy-dispersive X-ray analyzer attachment. It was found that the composite films on the hydroxyl-terminated silicon substrate showed better tribological properties than potassium stearate films under relative lower sliding velocity. At the load of 1.0 N, the composite potassium steartate film containing 40.0%wt ionic liquid slid 5000 cycles without failure, while the pure potassium stearate film only lasted 100 cycles. Transfer film was more easily formed on the counterpart steel ball with increasing the concentration of ionic liquid in the composite film. As a result, the tribological performance of the composite film was improved.