Boundary Lubrication and Lubricants

Lubricants are commonly used for reducing friction at, and wear of, interfaces. This chapter describes mechanisms of boundary lubrication and an overview of various types of lubricants and their properties. The chapter first presents data showing the effect of environment and types of lubricants and their interaction with solid surfaces on boundary lubrication behavior. Liquid lubricants include mineral (or petroleum) and synthetic organics. Various additives are used to improve specific properties. Additives are commonly used to modify friction and wear of lubricants and greases. These are classified as friction modifier, anti-wear and extreme pressure (EP). Greases are used where circulating liquid lubricant can not be contained because of space and cost and where cooling by the oil is not required or the application of a liquid lubricant is not feasible.