Selection and Application of Solid Lubricants as Friction Modifiers

Abstract

Solid lubricants are considered to be any solid material that reduces friction and mechanical interactions between surfaces in relative motion against the action of a load. Solid lubricants, used as a dry film or as an additive in a liquid, provide enhanced lubrication for many different types of applications. Graphite is most effective for applications involving high-temperature and high load-carrying situations. The effects of the lamellar structure of graphite can be observed when sliding conditions are applied onto metal surfaces. There are many types and sources of graphite. Graphite is characterized by two main groupings: natural and synthetic. Secondary synthetic graphite is derived from primary graphite that has been used for the fabrication of electrodes. Graphite possesses the necessary yield strength for successful lubrication. Molybdenum disulfide is the second significant solid lubricant widely used in industry. Boron nitride is a ceramic lubricant with interesting and unique properties. Polytetrafluoroethylene has been in use as a lubricant since the early 1940s.