**2.3 Wear and wear mechanisms**

Wear can be defined as damage to a solid surface, generally involving progressive loss of material, due to relative motion between that surface and a contacting substance or substances. Materials in contact are subjected to relative motion in many different applications. The creep and plastic deformation are not forms of wear per se because they do not produce wear debris but dimensional changes of the contacting surfaces. Also, corrosion is not directly related to wear because it can take place without any mechanical activation at all.(Buford 2004)
