Wear has been defined by a Committee of the Institute of Mechanical Engineers as: “Progressive loss of substance from the surface of a body brought about by mechanical action ( usually it reduces the serviceability of a body but can be beneficial in its initial stages in running in)”.
It is evident from this definition that what is desired in a gear lubricant is prevention of continuous wear. With highly loaded moving parts, which include gears, the following types of wear may occur:
(b) Corrosive wear
(c) Fatigue wear.
