Tribological Behavior of PTFE/PEEK Composite

Abstract

A study was conducted on tribological behavior of a PEEK-matrix composite with 20% (by volume) PTFE particulates. Neat PEEK and PTFE were also investigated to provide reference information for identifying the effect of PTFE inclusion on sliding friction and wear behavior of the composite. A comprehensive experimental program on friction and wear tests of the materials was developed and carried out with a precision pin-on-disk tribometer. Theoretical evaluation of the composite tribology was also made based on friction and wear mechanisms, and mechanical and thermal properties of individual constituents of the composite. The results show that solidstate lubricant PTFE particulates in the PEEK matrix decrease the PTFE/PEEK composite friction coefficient and wear rate appreciably by continuous formation of PTFE transfer films over the contact surface between the composite and the steel counterface. The specific wear rate of the composite was six times lower than that of the neat PEEK and two hundred times lower than that of the neat PTFE. Main friction and wear mechanisms of the composite included abrasive friction and wear of the PEEK matrix, PTFE adhesion and pull-out, formation of low-friction-coefficient solid-state transfer films, and shear flow of solid transfer films under combined compression and surface traction. High flash temperatures at the sliding contact surface were observed and determined in friction and wear tests of neat PEEK, PTFE and the composite. The parameter, i.e., the Peclet number, governing the temperature rise during sliding was obtained for each individual material. The temperature rise affected significantly the friction and wear behavior of the PTFE/PEEK composite, as both yield strength and hardness of the composite constituents decreased with the temperature rise, especially near their glass-transition temperatures.