by Ken Mantle CEF-2
Galling is a form of wear caused by adhesion between sliding surfaces. Galling is caused by a combination of friction and adhesion between surfaces, followed by slipping and tearing of crystal structure beneath the surface.(1) Sliding mechanisms that gall simply stop functioning or become erratic in their movement and in threaded components galling can cause mating parts to seize and not be able to be unthreaded or tightened.
While galling commonly occurs between sliding surfaces, or mating parts exposed to heat and/or pressure, some metals and alloys are more susceptible to galling due to the atomic structure of their crystals.(1) Examples of these metals are aluminum, titanium and stainless steel. These metals can lend themselves to galling with very little pressure or movement.
If you’re in the aerospace world you’ll recognize that these metals that are the most susceptible to galling are also the most commonly used metals in aerospace manufacturing. Titanium and aluminum are used because they are light metals and stainless steel is used for the corrosion resistance.
So how do we compensate for the galling susceptibility for these commonly use materials? In some cases simple lubrication can be applied to prevent galling. In other cases the use of dissimilar metals for mating parts can prevent the materials from causing wear and eventually galling.
The addition of coatings to machined components can be of particular interest in dealing with this problem. Certain spray lubricants, dry film lubes and PVD coatings have all found niches in minimizing galling potential.
CTI’s NP3 coating has been one of the most successful coatings used to prevent galling on stainless steel and aluminum aerospace components. From fasteners to couplings NP3 has become an industry standard for the prevention of galling.
This unique coating has its’ roots in solving the galling problem. NP3 was originally developed to prevent galling in stainless steel couplings used on oil rigs on the North Sea in the transfer of crude oil to barges.
Galling prevention coupled with the corrosion resistance, thickness uniformity and the self lubricating characteristics of our coating make NP3 an easy choice for the protection and longevity of aerospace and other machined components.
Contact Coating Technologies Inc. today and let us help with your project. Innovation is what we do. The absolute best in quality and customer service is who we are.
Wikipedia (1)