Static/dynamic friction and wear of some selected polymeric materials for conformal tribo-pairs under boundary lubrication conditions

This work is aimed at investigating the friction and wear performance of different polymeric materials having potential for hydraulic system components under lubricated sliding conditions against a steel counter face. A pin-on-disc test configuration was used for the experimental study. The different polymeric materials selected for these studies were commercial polyimides (PI), polyether ether ketone (PEEK), and flouropolymers. Some of these materials were bulk materials whereas others were used as coatings applied on to the cast iron substrate. The tribological characteristics of the polymers were compared with a reference grey cast iron. The frictional characteristics were evaluated in both static and dynamic conditions. The results have shown that by using polymeric materials it is possible to reduce breakaway friction by an order of magnitude compared to grey cast iron. However, the breakaway friction increased significantly after the wear tests. The polymeric materials having lowest breakaway friction have shown the highest wear with the exception of the PEEK-PTFE coating which showed low wear. PI with graphite fillers also showed low wear but it resulted in relatively high friction. The carbon fibre reinforced materials resulted in unstable friction as well as higher wear compared to the PI materials with graphite fillers.