ABSTRACT
Greases are non-Newtonian fluids and heterogeneous. Lubricating oil is immobilized by a thickening agent having a fibrous network, resulting in the formation of a semi-solid substance. A group of additives are added to the grease to obtain the desired properties. The lubricating oil, additives, and thickener play a synergistic effect to lubricate the interacting surfaces and protect them against friction and wear. In the past two decades, a variety of nanosized materials have been evaluated as additives of grease to improve its tribological performance. The nanosized additives demonstrated excellent antiwear and load-bearing capacity than prevailing additives. Conventional grease is made up of mineral or synthetic oil and metallic or non-metallic soaps that are not biodegradable. Therefore, the direct disposal of conventional grease in the environment shows an adverse effect on living beings. Due to environmental concerns, researchers are trying to find a sustainable alternative that can perform at par or better than conventional grease. Vegetable oils with a high flash point, good metal adherence, and excellent lubrication property have high potential as bio-lubricating greases and attract the attention of lubrication engineers. In recent years, investigations on vegetable oil-based grease have been carried out extensively by various researchers. This chapter is focused on the current trends in the development of lubricating grease and its lubrication behavior.
