Frictional characteristics of thin polytetrafluoroethylene films deposited on glass by hot filament chemical vapor deposition method

The immediate aim of this work was to develop a method that is reliable and repeatable for examining the frictional characteristics of Polytetrafluoroethylene (PTFE) films deposited by HFCVD method on glass substrates. The second objective was to use the developed method to examine the effects of HFCVD process parameters on coefficient of friction (COF), under the established measurement conditions. A Universal Micro-Tribotester (UMT) was used in the ball-on-flat configuration to examine the effect of COF. The effects of normal force, sliding speed and film thickness on the frictional behavior of the PTFE film were tested for a wide range of these parameters. Optical microscopy was used to examine the wear tracks of the PTFE films. In addition, durability of the PTFE films was examined by monitoring the change of COF in ball-on-disk tests. Considerable variation was observed in the COF value of PTFE film tested at various measurement conditions. In particular, PTFE exhibits a low COF at slow speeds and high normal forces; compared to a high COF at high speeds and small normal forces. The relative importance of HFCVD process parameter levels on COF was observed by monitoring its effect on COF. It was found that film deposition parameters of the HFCVD method, namely gas pressure, filament resistance and wafer-to-filament distance have relatively minor effects on the COF of the thin PTFE films deposited on glass.