Tracking Wet Friction Performance Via Energy Dispersive X-Ray Spectroscopy

This paper describes a technique which uses Energy Dispersive X-ray Spectroscopy (EDX) to track progressive changes in wet friction material surface chemistry as the material is cycled under various energy and temperature conditions. Using this technique, elements can be identified on the surface and compared with the base friction material and fluid chemistries to obtain a quantitative measure of chemistry changes at the interface. Performance effect of surface chemistry change can be obtained by corresponding measurement of the coefficient of friction. Additionally, surface chemistry changes can be compared with progressive changes in friction material degradation as measured by Thermogravimetric Analysis (TGA) after identical conditions of use.

Surface chemistry change and mating surface temperatures have been measured versus cycles at several energy loadings. Separate tests have been performed to follow friction material degradation changes during cycling.

The results show that performance correlates closely with surface chemistry changes that occur dependant on surface temperature/time conditions produced by the energy/power loadings of the application. Friction material degradation is an separate mode of change which is also dependant on the energy/power loadings of the application. The EDX technique provides a method of distinguishing between these changes, leading to a better understanding of failure modes and the energy/power, time/temperature conditions under which these modes occur.