Galling

Galling usually refers to the adhesive wear and transfer of material between metallic surfaces in relative converging contact during sheet metal forming and other industrial operations.

In engineering science and in other technical aspects, the term galling is widespread. In recent years, there have been attempts to standardize or redefine the word in coordination with greater understanding of the involved frictional mechanisms. ASTM International has formulated and established a common definition for the technical aspect of the galling phenomenon in the ASTM G40 standard: "Galling is a form of surface damage arising between sliding solids, distinguished by microscopic, usually localized, roughening and creation of protrusions, (i.e. lumps, see figure 1), above the original surface".