Tribological or anti-friction coatings are used for dry lubrication of materials. For this purpose anti-friction coatings may only show low coefficients of friction and weak adhesion to their friction partners. To achieve this, there are various approaches to comply these demands. Solid lubricants such as graphite or PTFE particles can be incorporated into the coating or polymer resins can be optimized by means of structural modification to a minimum of frictional resistance.
For the use of coatings in tribological applications, the entire tribological system must be considered. This includes stress systems with movement pattern, course of movement, strain, sliding speed, sliding surface temperature, sliding distance traveled and the structure of the tribological system, which is described by hardness, roughness and interaction with the friction partner. The characterization of the tribological system is essential for the development of anti-friction coatings. The modification of polymer resins is especially suitable for low to medium stress systems, while particle lubrication is mostly used for high stress systems. The boundary layers are crucial for the friction behavior. Therefore, a tribological coating has to be optimized for the specific application.
The measurement of the friction coefficients is carried out with a tribometer. There are various architectures of tribometers. To simulate the stress system of an application, the materials used in tribometers are as similar to this application as possible.
Using tribological coatings containing solid lubricants, the lubrication between the friction partners is carried out by particles getting into the friction gap by abrasion from the coating. Furthermore the usage of micro-encapsulated solid or liquid lubricants is possible, which can be released by means of a chemical or physical trigger.