Effects of counterface surface roughness on friction and wear of PEEK materials under oil-lubricated conditions

The effects of counterface surface roughness on the friction and wear behaviors of polyether ether ketone (PEEK) are studied using blocks on a ring wear tester under oil-lubricated conditions. The blocks are made of unfilled PEEK and a PEEK composite that is 30 wt% carbon fiber. The ring is made of forged steel (SF540A) and its surface roughness varies between 0.04 to 1.86 μm Ra ; the sliding velocity and load are 10.2 m/s and 588 N, respectively. Results indicate that both the friction coefficient and each block's specific wear rate increase from low to high values when the ring's surface roughness exceeds a certain value (0.2-0.4 μm Ra ). In high friction and wear regions, significant differences exist in the friction and wear behaviors of both PEEK and the PEEK composite. The PEEK composite shows a significantly lower friction coefficient and wear rate as compared to PEEK. However, the PEEK composite causes greater wear of the ring, though the extent to which the ring wears is dependent on the ring's surface roughness. Wear particles and wear scars on both materials are observed and analyzed using a scanning electron microscope and an energy-dispersive X-ray spectroscope. The wear mechanisms are then discussed. © 2016 Japanese Society of Tribologists.