Effect of reinforcement morphology on high-speed sliding friction and wear of PEEK polymers

Advanced engineering polymeric materials such as poly-ether-ether-ketone (PEEK) are increasingly being used for challenging tribological application. Some of these applications involve severe contact conditions. Reinforcing materials such as carbon fiber are often incorporated into polymeric materials to improve mechanical and thermal properties. In the present study the friction and wear behaviour was evaluated for various PEEK disc materials in high-speed (up to 65 m/s) sliding contact with 440C stainless steel balls using a 3 ball-on-flat contact configuration. Two of the tested PEEK materials were reinforced, one with long woven fiber and one with short, randomly oriented fibers, in addition to a base PEEK with no reinforcement. In general, at high sliding speeds, the friction and wear behaviour is related to the morphology of the reinforcement through the mechanisms of polymer transfer layer formation, abrasive wear rate of the steel ball, and thermal management of frictional heat generation. Under the current test conditions it is shown that the material with long woven reinforcement exhibits the lowest wear rate and lowest friction at high sliding speeds.