On the friction and wear behaviour of PAN- and pitch-carbon fiber-reinforced PEEK composites

High temperature (HT) composites possess several advantages concerning thei r friction and wear behaviour. Polyetheretherketone (PEEK) composites espec ially show a low specific wear rate even at higher temperatures. They are u sed in many applications like journal bearings or piston rings. The frictio n and wear behaviour of carbon fiber reinforced PEEK has been investigated in detail earlier. The present report deals with the investigation of the f riction and wear performance of different types of carbon fibers in PEEK co mposites, especially polyacrylonitrile (PAN) vs, pitch based carbon fibers, against a 100Cr6 steel counterpart. The pitch based carbon fiber possess l ower mechanical properties than PAN-CF, and the diameter of the pitch-CF is much bigger. Due to these differences it is expected that pitch-CF show a completely different friction and wear property profile. Tests have been pe rformed on a pin-on-disc device. Two different speeds (1 m/s and 3 m/s) and pressures (I MPa and 3 MPa) have been adjusted. The materials were investi gated at room temperature and at 150 degrees C. Worn surfaces were examined by laser profilometry and scanning electron microscopy (SEM). First result s show that the friction and wear behaviour of the pitch-CF reinforced PEEK at higher pressures is not as good as that of the PAN-CF reinforced PEEK, whereas at higher speeds, the friction and wear performance of the pitch-CF /PEEK composite is slightly better. A clear superiority of the pitch- over the PAN-CF/PEEK is evident when both are modified with internal lubricants such as PTFE and graphite. At an equivalent tribological performance of the two systems, preference should be given to the pitch-CF/PEEK, because of t he much lower price level in comparison to PAN-CF. (C) 1999 Published by El sevier Science S.A. All rights reserved.