Question

Explain the mechanism of Extreme pressure lubrication.

Answer 1

Under heavy load and high speed operating conditions, large amount of frictional heat is generated Under these conditions a liquid lubricant fails to stick and may decompose. To withstand such extreme conditions, special additives are added to the lubricating oil. Additives  are generally organic compounds having active radicals or group such as chlorine, sulphur, phosphorous etc. They react with the metal surfaces at high temperature and form durable
films of metaJJicchlorides, sulphides and phosphides. These compounds posses high melting point and good thermal stability and hence , serve as good lubricant. However, they are not effective on chemically inert metal surfaces of Ag, Ti, and Cu. This type of lubrication is used for cutting tools, in wire drawing, rocket crushing machines etc.