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

High temperature (HT) composites possess several advantages concerning their friction and wear behaviour. Polyetheretherketone (PEEK) composites especially show a low specific wear rate even at higher temperatures. They are used in many applications like journal bearings or piston rings. The friction and wear behaviour of carbon fiber reinforced PEEK has been investigated in detail earlier. The present report deals with the investigation of the friction and wear performance of different types of carbon fibers in PEEK composites, especially polyacrylonitrile (PAN) vs, pitch based carbon fibers, against a 100Cr6 steel counterpart. The pitch based carbon fiber possess lower 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 performed 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 investigated at room temperature and at 150 degrees C. Worn surfaces were examined by laser profilometry and scanning electron microscopy (SEM). First results 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 the much lower price level in comparison to PAN-CF. (C) 1999 Published by Elsevier Science S.A. All rights reserved.