Performance coatings fall into four general categories:
Dry Film lubricants
It should be noted that some coatings will fall into more than one category. You might have, as an example, a Corrosion Inhibitor that is also a Thermal Dispersant or Thermal Barrier. The following information will provide a general overview on coatings falling into these categories. (Click on a category above to go directly to it)
Dry film lubricants,
Dry film lubricants also known as solid film lubricants, provide a lubricating film that reduces friction, inhibits galling and seizing and in some instances can aid in dispersing heat. The appearance is generally a charcoal gray and takes on sheen upon burnishing. They are slippery and provide an extremely low coefficient of friction.
The two most important components are the binders and lubricating ingredients. Without a good binder the coating will not stay in place and will simply cold flow or buff off in operation. Similar coatings using the same pigments but different binding systems can show a wide variation in load carrying abilities, ranging from 100,000 psi to over 350,000 psi. The pigments determine the actual lubricating potential. PTFE, as an example, (PTFE known by the DuPont brand name Teflon) is listed as having the lowest coefficient of friction (COF). However, under high speed and load, the COF of PTFE degrades while that of MOS2 (Moly) improves. MOS2 is significantly better than PTFE at high speeds. Selecting the proper ingredients can make or break a coating.
MoS2 (Molybdenum Disulfide) with particle sizes in the range of 1-100 µm is a common dry lubricant. Few alternatives exist that can confer the high lubricity and stability up to 350 °C in oxidizing environments. Sliding friction tests of MoS2 using a pin on disc tester at low loads (0.1-2 N) give friction coefficient values of <0.1