Effect of Counterface Material on Dry Sliding Wear of PEEK-PTFE Composites

The addition of polyetheretherketone (PEEK) filler to polytetrafluoroethylene (PTFE) is known to result in an orders-of-magnitude decrease in dry sliding wear of PTFE. Unlike similar ultra-low wear PTFE composites, PEEK as a filler is particularly effective since ultra-low wear of PEEK-PTFE is insensitive to environmental moisture. Mechanisms of low wear in PEEK-PTFE, i.e., formation of tenacious transfer films is hypothesized to occur independent of tribochemically generated functional groups, relying instead on intrinsic polar sites within the PEEK polymer chain. The present study aims to probe whether tribochemistry-independent mechanisms of low wear in PEEK-PTFE operate when sliding against substrates with different material chemistries. Specifically, we test the hypothesis that PEEK-PTFE composites are able to sustain low wear against a range of counterface materials, in particular non-ferrous alloys, through tribochemistry-independent mechanisms similar to those which operate under low moisture environments. Results of this work show that wear rate against steel, brass and aluminum alloys vary between 10(-7) and 10(-6) mm(3)/Nm, driven largely by the properties (coverage, thickness and roughness) of resulting transfer films. Interestingly, spectroscopic analyses of interfacial films reveal no significant differences after sliding on the different substrates, which suggest that mechanisms of low wear operate independent of the choice of counterface material.