A study of the wear damage of a PTFE coating: The effects of temperature and environment on its mechanical and tribological properties

In this study, a methodology was set up to obtain a measure of the durability of PTFE coatings. Tribological tests to study the effect of both temperature (from 25 degrees C to 180 degrees C) and environment (dry, in water, and in oil) on the mechanical and tribological properties of PTFE were carried out. Interactions between the effects of temperature and environment were also investigated. As expected, the experimental results showed that the wear resistance of PTFE significantly decreases with an increase in temperature. Measurements of the mechanical properties of the coatings by nanoindentation at different temperatures confirmed a change in the mechanical properties of the PTFE coatings with increasing temperature. The tribological properties were evaluated through the evolution of the coefficient of friction as a function of temperature and the morphological study of wear debris by scanning electron microscopy (SEM). In addition, the coefficient of friction exhibits no significant difference as a function of the environment. Examination of transfer film formed under various conditions helped us understand the various wear mechanisms occurring during these tests and indicated that the formation of an adhered and persistent transfer film was directly linked to the wear performance of the PTFE coating. In particular, higher wear observed in the oil environment could be attributed to a different tribological behavior of the transfer film on the abrasive counterface, namely poor adhesion, resulting in an ease of removal and replenishment with successive rubbing cycles.