The effects of initial and in-situ generated roughness on polymer wear: Voluntary vs. involuntary

Polymer wear against a metal surface depends on both the voluntary, pre-defined roughness and the involuntary, in-situ generated roughness by the polymer wear. Using highly defined roughness manufactured on stainless counterfaces with laser-surface-texturing (LST), a new roughness directionality parameter (IRMS), two established ultralow wear polymers (5 wt% α-Al2O3−PTFE and 20 wt% PEEK-PTFE), reciprocating pin-on-flat tribometry and two sets of relevant data in the literature, we systematically studied the variance of polymer wear and transfer with the initial and in-situ generated counterface roughness. While no consistent relation was found between roughness and wear rate, strongly linear relations were noticed between worn surface directionality and polymer wear volume at the low wear transients. The results support the working hypothesis and suggest the involuntary roughness effects could be 1) dominant as they easily destabilize the transfer film, 2) quantified using the newly defined roughness directionality.