Ionic Liquids As Additives to Cutting Fluids to Reduce Machine Tool Friction and Wear

Abstract

In manufacturing processes, the cost of tooling contributes to a significant portion of operating costs. Several papers have been dedicated to various improvements on tool life, including monitoring the effect of temperature conditions and flood cooling. Flood cooling is not economical, so research has also been done to investigate minimum quantity lubrication and the effects of different additives, such as nanofluids. Another additive, ionic liquids, have become popular in tribological studies because they have unique properties that allow them to form ordered molecular structures, which is ideal in lubrication. Research has proven ionic liquids to be effective in reducing wear and friction coefficients. Currently, utilizing ionic liquids specifically to reduce tool wear has been almost exclusively limited to titanium and steel applications. The goal of this study is to improve tribological performance of the subtractive manufacturing process using ionic liquid add-ins to widely available machine shop coolants and oils. A series of reciprocating ball-on-flat experiments will be conducted using a 1.5mm diameter 250 Chrome Steel G25 ball and 6061-T6 aluminum disk to simulate cutting conditions often seen in manufacturing processes. 6061 Aluminum is an alloy commonly seen in machine shops and large-scale manufacturing scenarios because of its versatile material properties and wide availability. The tests were run at constant sliding distance, velocity and load. The lubricating mixtures were prepared by adding 5 wt % of a phosphonium based ionic liquid, Trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide ([THTDP][NTf2]), to the base fluids Trim Sol™ emulsion fluid and Mobilmet™ 766 high performance neat cutting oil. The addition of the ionic liquid to both base lubricants (oil and coolant) increased the friction coefficient (18.60% and 4.89%, respectively) while the wear volume was reduced (28.75% and 7.84%, respectively). The results for the oil provided evidence that the ionic liquid did have an effect to reduce wear, however, the same conclusion could not be drawn for the coolant.