Wear resistant solid lubricant coating made from PTFE and epoxy

A composite coating of polytetrafluoroethylene and epoxy shows 100 · improvements in wear resistance as compared to either of its constituents alone and reduced friction coefficient under testing on a pin-on-disk tribometer. This coating is made by impregnating an expanded PTFE film with epoxy, which provides three unique functions: (1) the epoxy compartmentalizes the PTFE nodes, which is believed to reduce the wear of the PTFE, (2) the epoxy increases the mechanical properties such as elastic modulus and hardness, and (3) the epoxy provides a ready interface to bond the films onto a wide variety of substrates easily and securely. The experimental matrix had normal loads of 1–3 N, sliding speeds from 0.25 to 2.5 m/s, and used a 2.4 mm radius low carbon steel pin in a rotating pin-on-disk tribometer. The skived PTFE films had wear rates on the order of K 1⁄4 10 mm/Nm and friction coefficients around l 1⁄4 0.2. Both the high density films (70 wt%PTFE) and low density films (50 wt% PTFE) had wear rates on the order of K 1⁄4 10 mm/Nm and friction coefficients around l 1⁄4 0.15. The neat epoxy films showed significant scatter in the tribological measurements with wear-rates on the order of K 1⁄4 10 mm/Nm and friction coefficients around l 1⁄4 0.40. The enhanced tribological behavior of these composites is believed to stem from the coatings ability to draw thin PTFE transfer films into the contact from the nodes of PTFE, which act like reservoirs. Nanoindentation mapping of the coatings and the transfer films supports this hypothesis, and accompanies scanning electron microscopy observations of the worn and unworn coatings.