Dry film lubricants are much more than low friction coatings. That's right. They can be used for metal wear protection, too. Especially when surface contact is severe and localized. Ironically, this is the time when lubrication, not hardness alone, is key.

Does your surface condition fall within these types of wear or contributing factors?

Wear Adhesion –– visible by fretting, pits, holes or scales transfer, the result of softer materials dislodging from a widened hardness gap between two moving surfaces. Besides a drop in performance, look for visible changes in surface finish, dimensional or geometric distortion.

Wear Abrasion –– witnessed by scratches, grooves, or corrugations, caused by loose abrasive particles torn away from the wear surface. Also look for negative changes in performance, surface finish, dimensional or geometric distortion.

Wear Surface Scarring –– seen by tears or small holes, typically relates to shock or impact, and involves fatigue close to the wearing surface.

Wear 'Tribo' Oxidation –– involves oxidation products from the wearing surface, usually in particulate form. Often harder than their parent metals, surfaces become rough which, in turn, leads to abrasive or adhesive wear.

Dry film lubricants may be just right for you.

What are dry film lubricants? See them as solids used between two surfaces in relative motion, for the purpose of reducing wear, lowering friction.

Known also as solid films, they're best often utilized in extreme environments, such as very high temperature or extreme pressure, where organic–based compounds would degrade or 'cold–flow' and never survive.

Examples of frequently applied compounds include graphite, tungsten disulfide (WS2), and molybdenum disulfide (MoS2). Their material characteristics work similarly, in that each exhibits high ductile shear under an applied tangential force.

Imagine a series of vertically stacked plates (called basal planes) supported by long, wobbly legs (weak Van der Waals forces). Under an applied lateral force, the legs 'collapse'. Severe plastic flow occurs. The plates shift out of place. Yet strong ionic bonds force the shear parallel with the basal planes, perpendicular to the crystal structure, their preferred orientation.

Want to prevent wear? Then reduce your metal–to–metal contact. Be sure the lubricating system is comparatively softer than the bearing material to avoid abrasive wear. Know the service temperature of your environment and heat stability of your lubricant.

Machinery offers excellent areas for application. As do cutting tools, dies, and forming tools. Gears, too, where contact stress is high and plastic deformation (of the parent metal) likely.

Industrial lubricants may be applied in a variety of ways. From basic immersion, spray, brush, dip, burnish, impact or impingement, to sputtering and heat fusion alloys. Generally, they are applied in pure thin films (less than 0.0001 inch). Or, as resin–bonded systems whose thickness is typically 0.0002 inch or greater, using binders such as epoxy, phenolic, or ceramic. Other forms of application include plasma sprays (.003 inch and higher), where lubricating solids are interspersed in a wear resistant matrix. For internal surfaces beyond line of sight, outside the practical PV limit of co–deposited plating, the use of self–lubricating powder metallurgy composites may be preferred.

Which surface should be coated? Consider one side, or both. For a hard/soft bearing system, coating the softer of the two surfaces will extend the life of the system. However, the harder a substrate, the more effective the dry film lubricants will perform.

Generally, friction will be slightly higher coating both surfaces, rather than coating one surface only. But wear life will increase coating both surfaces. So, while differences may be negligible in your application, you may have to determine whether longer wear life or better performance is best.

Today, there are some exceptionally high performance products available for adverse conditions. Some perform in temperatures ranging from cryogenic to ultra high (1100 degrees Celsius). Others are compatible with liquid oxygen, perform in hard vacuum, resist high frequency fretting wear, and loads up to 250,000 psi.

So, what are the makings of a good, wear–resistant coating? Next time, take a serious look at dry film lubricants.

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