Improved Loss-of-Lubrication Performance with Lubricants Containing Nano-Graphene Platelets and Ionic Liquids

Abstract

In this study, nano-graphene platelets (NG) and a phosphonium-phosphate-based ionic liquid (IL) were studied as additives to rotorcraft gearbox oil to improve the resistance to scuffing under starved lubricated conditions. Behavior under a loss of lubrication was evaluated using a high-speed ball-on-disk tribometer and a reciprocating cylindrical pin-on-disk tribometer. In addition, the scuffing load and friction over a wide range of sliding and entrainment speeds was determined. On the high-speed ball-on-disk tribometer, an oil blend containing both NG and IL additives was able to operate two times longer than an unadditivized oil before scuffing after the lubrication supply was removed. The increase in time to scuffing was larger for two additives together than the sum of their parts. The additives showed an increase in scuffing load individually but were detrimental when mixed together with a lower scuffing load. The combination of NG and IL show promise as additives to increase the operation time of gears during loss of lubrication, however at the potential cost of decreasing the load-carrying capacity of the oil.

Keywords

• staved lubrication
• ionic liquids
• graphene
• friction