Dry Film Lubricants Low Friction Coatings
Dry film lubricants low friction coatings can be excellent means to achieving low friction.
Unlike greases, oils, or ‘wet’ lubricants, dry film lubricants low friction coatings can be utilized in extreme environments, such as very high temperature or pressure, even under vacuum, where other, organic-based compounds like PTFE (polytetrafluoroethylene) will ‘cold flow’, never survive.
Examples of common lubricating compounds include graphite, tungsten disulfide (WS2), and molybdenum disulfide (MoS2). Frictional performance can be exceptional from these unique structures, with coefficients as low as 0.02-0.04. Of course, friction is a system-dependent parameter, a function of load, travel distance, rate of travel, temperature, base material hardness, surface finish, mated surface characteristics, and other factors.
How is their performance derived? Characteristics of dry film lubricants low friction coatings come from lubricating particles rubbing against themselves. There is no metal to metal contact. Of course, special binders, both organic and inorganic based, are often included for a variety of physical property or performance enhancements.
Dry film lubricants low friction coatings rely on hardness of the moving parts they cover. That is why base material selection is so important. Thickness ranges from 0.0001 to 0.0005 inch are typically all that is needed to derive sustainable low friction. Today, these materials can be applied by spray, wipe or dip, and, from the more advanced techniques, vapor deposition. Consequently, coverage of most any geometry, any surface, internal or external, will be feasible. Processing temperatures can be as low as room temperature but average about 400 degrees Fahrenheit. This makes most metals acceptable candidates so long as they meet other critical mechanical requirements for the ‘system’.
Here, though, surface finish will be critical. All roughness (peaks) between the surfaces needs to be removed. Otherwise, the very benefits of dry film lubricants low friction coatings may be negated, and severe galling or cold-weld may occur. Generally, for both sliding surfaces, cast materials are poor work piece candidates, unless surface finishes of 32 micro inch or better are assured.
Between the sliding surfaces, how many surfaces should you apply dry film lubricants low friction coatings? Generally, friction will be slightly higher coating both surfaces, rather than coating one surface only. But by coating both surfaces, you may may extend the life of the ‘overall system’. So, while differences may prove negligible, this is something you will have to determine. That is, whether longer wear life or lower friction is the choice for your gear, machinery, or metal lubrication.
Dry film lubricants low friction coatings have a long established history with the military and aerospace industries. Their ability to work in some of the more adverse environments is well known, including temperatures ranging from cryogenic to 2000 degrees Fahrenheit, compatibly with liquid oxygen, in a hard vacuum, and to withstand high frequency fretting, as well as loads in excess of 200,000 psi. Of course, this makes them proven candidates for automotive, marine, and countless other industries.
To be sure dry film lubricants low friction coatings will best serve your needs, first understand your requirements. What is the nature of your environment? Are the materials you’ve chosen for your work pieces suitable? Have they been hardened?
Often, failure is not the fault of the coating, but a failure to understand its limits. Know this, then ask all the right questions and surface engineer for success every time.