Tribological Sensitivity of PTFE/Alumina Nanocomposites to a Range of Traditional Surface Finishes

Wear tests were performed with polytetrafluoroethylene (PTFE) + Al ₂ O ₃ nanocomposites on various manufactured surfaces to determine whether or not the wear resistance of these nanocomposites is a strong function of surface preparation. Four different surface finishes of grade 304 stainless steel counterfaces were used: electropolished (R _q = 88 nm), lapped (R _q = 161 nm), wet-sanded (R _q = 390 nm), and dry-sanded (R _q = 578 nm). PTFE + Al ₂ O ₃ nanocomposites made from powders of roughly 2-20 μm PTFE (matrix) and ∼44 nm Al ₂ O ₃ (filler) were prepared at filler weight percentages of 0, 1, 5, and 10% and tested on each surface finish. Additionally, 5 wt% 44-nm nanocomposites were compared to identically prepared 5 wt% 80- and 500-nm Al ₂ O ₃ filled PTFE composites on each surface. Friction coefficients were between 0.12 and 0.19 and wear rates decreased from K = 810 × 10^{− 6} mm ³ /(Nm) for the 5 wt% 500-nm alumina-filled PTFE on the dry-sanded surface to K = 0.8 × 10^{− 6} mm ³ /(Nm) for the 5 wt% 80-nm filled composite on the lapped surface. It was found that the minimum wear rate occurred on the lapped counterface for every composite, and the wear rate is a strong function of the transfer film thickness and morphology.

KEYWORDS:

• Solid Lubricants
• Nanocomposites
• Friction and Wear
• Surface Roughness

ACKNOWLEDGMENTS

This material is based on work supported under National Science Foundation (NSF) grant no #CMS-0219889, GOALI: Collaborative Research: Tribology of Nanocomposites and AFOSR-MURI grant FA9550-04-1-0367. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF or the Air Force Office of Sponsored Research.

Presented at the ASME/STLE Tribology Conference in Long Beach, California

October 24-27, 2004 Manuscript approved October 13, 2004

Review led by Robert Fusaro