Tribological Analysis of Bis(2-Ethylhexyl) Phosphate Ionic Liquid Based Bio-Lubricants at Various Operating Conditions

Abstract

Mechanical components involving surface interaction requires lubrication at all costs to reduce friction and wear in order to avoid mechanical failure. Majority of lubricants used around the world are from mineral based sources. These sources are not infinite and pose danger to the environment due their toxic nature and disposal problems. This awareness has given rise to the formation of environmental friendly lubricants which are obtained from renewable sources such as bio-lubricants. The low thermal stability of bio-lubricants has caused the limitation on it use as compared to mineral based oils. Certain additives are used to increase the thermal stability of these bio-lubricants and further enhance their tribological properties. Ionic liquids are the most common solvents used as an additive to the bio-lubricants. These organic salts are environmentally friendly and have proved to be beneficial to the tribological properties of bio-lubricants. The extent to their effectiveness in enhancing the tribological performance of a lubricants greatly depends upon compatibility and its miscibility. Ionic liquids are generally composed of anions and cations and make strong interaction with polar base oils. In this research work, Bis (2-Ethylhexyl) phosphate ionic liquid was used an additive to the base test lubricants including PAO and bio-lubricants as Cotton seed oil (CSO), Rattan jot oil (RJO), Waste cooking oil (WCO) at various operating conditions. A four ball tribometer was used to perform the tests for all lubricants with and without the addition of ionic liquid as an additive. To analyze the wear scar diameter on each sample a digital microscope was used. Results were obtained and analyzed, and it was found that addition of ionic liquid has not much improved the performance of PAO but significant effects can be seen for the case of bio lubricants. Where CSO performed best at lower operating loads and RJO performed best at higher operating loads due to its inherent load carrying capacity.