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Thermal Coatings
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 a 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.
One of the obvious reasons for using a lubricating coating is to reduce friction, which improves wear, extends part life and frees up H.P. normally lost to friction. A second major benefit is a reduction in part temperature. This is especially important to such parts as valve springs. Here the pigment choice is critical as certain ingredients can trap heat in a part. Not all coatings are created equal. .
Thermal Barrier Coatings (TBC’s) are designed to reduce the movement of heat. In some instances, such as exhaust systems, you want to keep the heat within the part. In combustion chambers you want to use the heat generated by combustion to push down on the piston rather than bleed off into surrounding surfaces. Due to continued testing we are learning that simple thermal barrier action is not the only characteristic that is important. In fact certain TBC’s will move an engine into detonation. TBC coatings can be made from a variety of materials. Ceramics get the most attention, though there are other materials that are superior in specific applications. The proper choice is critical to the overall function of the coating.
Being able to move and control heat is of tremendous importance. For this thermal dispersants (TD) are used. Excessive temperature can lead to metal fatigue, boiling fluids, damaging metal expansion, reduce electrical efficiency and a host of other problems. Traditionally dealing with heat has been handled either by expanding the radiating surface, constructing parts from materials that are more heat conductive and using the color black. With advances in thermal management methods additional ways of enhancing heat transfer now exist. Individual products can be utilized by themselves or in conjunction with other coatings to manage the flow of heat. Thermal dispersants are capable of transferring heat faster than the bare metal surface. While Thermal dispersants do make use of the color black, The thermal dispersants are more than a simple "black body" heat emitting coating.
Dan
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