Explain the mechanism of boundary and Extreme Pressure Lubrication.
Answers
Explanation:
This chapter discusses boundary and extreme pressure (EP) lubrication as a complex phenomenon. The lubrication mechanisms involved can be classified in terms of— relative load capacity and limiting frictional temperature. These lubrication mechanisms are usually controlled by additives present in the oil. As, the cost of a lubricant additive is usually negligible compared to the value of the mechanical equipment, the commercial benefits involved in this type of lubrication can be quite large. In general, boundary and EP. lubrication involves the formation of low friction, protective layers on the wearing surfaces. One exception is when the surface-localized viscosity enhancement takes place. The occurrence of surface-localized viscosity enhancement is extremely limited. The operating principle of the boundary lubrication regime is illustrated by considering the coefficient of friction. Lubrication by chemical and physical interaction between an oil-based lubricant and a surface (usually metal) is essential to the operation of most practical machinery. Four basic forms of this lubrication are identified: (1) the formation of an ultra-viscous layer close to the worn surface, (2) the shielding of an oxidized metal surface by a mono-molecular layer of adsorbed linear surfactants, (3) the separation of contacting surfaces by entrapped layers of finely divided and perhaps amorphous debris, and (4) the suppression of metal to metal contact at extreme pressures by the temperature dependent formation of sacrificial films of corrosion product on worn metallic surfaces.
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