Requires repetitive compressive stresses.
Potentially Occurs in:
Gear teeth, rolling element bearings, surface-treated parts, riveting tools, hammers, static overload.
Pitting can occur in a number of wear processes. Pitting is the removal or displacement of material by a fatigue action that forms cavities on a surface. Pitting, as part of surface fatigue, frequently occurs in rolling element bearings, gears, worm wheels and cam paths.
Spalling arises from the same mechanisms as pitting, and in this form of wear, particles fracture from a surface in the form of metal flakes. This is the result of surface fatigue, and it occurs in the same types of systems. Occasionally, wear surfaces that are subject to rolling elements are electroplated for wear resistance. Such systems are very prone to spalling.
Impact wear, repetitive impacting of two solid surfaces, causes material damage and removal. A simple example of impact wear is damage that occurs on the head of a high-speed riveting hammer. The hammer drastically deforms the rivet head, and there is no concern for the wear that occurs on the rivet, but the hammer suffers material attrition that eventually necessitates its replacement.
Brinelling is the wear term used to describe surface damage of solids by repeated local impact or by static overload. The origin of this term is from the resemblance of this form of damage to a hardness indentation on a Brinell hardness test