Galling

From GAWDAwiki

Galling, sometimes known as cold welding, is a form of severe adhesive wear which can occur when two metals are in relative motion and under sufficient load to permit the transfer of material. Severe galling can result in seizure of metal components. The key factors affecting the tendancy for galling are design tolerances, surface finish, hardness and microstructure of the metals in contact.^{[1] [2]}

An example of galling is when the threads of nuts and bolts are forced together, causing friction among the asperities (high spots) on the surface. The friction causes heat, which is mainly isolated to these asperities. The asperities weld together; further displacement then causes these tiny welds to break, which makes the surface even rougher, creating more opportunity for friction. Lubricants protect against galling (anti-galling).^[3]

Reference

1. http://www.bssa.org.uk/topics.php?page=2&category=7
2. http://metals.about.com/library/bldef-Galling.htm
3. http://www.dynamiccoatingsinc.com/antiSeize.htm