Stainless Steel Ratchet Maintenance and Care
Galling and its CONTROL
What is Galling?
Galling is a form of wear caused by adhesion between sliding surfaces. When a material galls, some of it is pulled with the contacting surface, especially if there is a large amount of force compressing the surfaces together. Galling is caused by a combination of friction and adhesion between the surfaces, followed by slipping and tearing of crystal structure beneath the surface. This will generally leave some material stuck or even friction welded to the adjacent surface, whereas the galled material may appear gouged with balled-up or torn lumps of material stuck to its surface.
Galling is most commonly found in metal surfaces that are in sliding contact with each other. It is especially common where there is inadequate lubrication between the surfaces. However, certain metals will generally be more prone to galling, due to the atomic structure of their crystals. For example, aluminium and Stainless Steel are metals that will gall very easily, whereas annealed (softened) steel is slightly more resistant to galling. Steel that is fully hardened is very resistant to galling. Galling is adhesive wear that is caused by microscopic transfer of material between
metallic surfaces, during transverse motion (sliding). It occurs frequently whenever metal surfaces are in contact, sliding against each other, especially with poor lubrication.
How to control galling.
Reduce friction is the key by lubrication. There are a wide range of lubricants containing nickel, molybdenum, copper, silver or graphite or combinations of these. They can be messy. Those primarily containing nickel are more suitable for high temperatures. Two suppliers of nickel and graphite containing anti-seize compounds are Devcon and Loctite. Their websites offer selection tables depending on service requirements. WD 40 can also be used, but as its name suggests it's a water displacement product.
This document was compiled with extracts from Wikipedia and the Australian Stainless Steel Development Association ASSDA.
