Galling in Materials

Galling refers to a very severe type of wear in which microscopic particles of the material of one component is transferred to the other component.  This occurs due to severe mechanical wear which can cause the materials to fuse due to heating. 

This type of wear, generally,  occurs in components which have high load and which operate at low speed.  Poor lubrication is also a reason for galling.  Galling if normally found in components such as bearings, pistons of IC engines and in shafts. 

Hardened materials have a lower tendency to tall.  Soft materials are more vulnerable to galling.

Galling can be prevented by ensuring adequate lubricating and by choosing the materials of the mating surfaces carefully.  The materials can be from materials with different hardness levels such as different grades of steel. 

Bolts are particularly vulnerable to galling action.  Due to improper tightening techniques heat can be generated between the bolt and the thread.  Ensuring proper tightening techniques which prevent heat generation can prevent galling.