SURFACE-FILMS AND SOLUBLE DEGRADATION PRODUCTS FORMED IN A PFPAE FLUID AND THEIR IMPLICATIONS TO THE WEAR OF STEEL

The soluble degradation products were generated in a linear perfluorop olyalkylether (PFPAE) fluid in boundary lubrication. Perfluoropolyalky lether carboxylic acid species were found in the residual fluids from the sliding tests by vibration spectroscopy. Surface-bound organic and inorganic reaction products were identified by vibration microspectro scopy with a grazing angle objective attachment and X-ray photoelectro n spectroscopy (XPS), respectively. Inorganic surface films were found to be composed primarily of FeF3. A monodentate perfluorocarboxylate surface species was found on the sliding surfaces in 50 degrees and 10 0 degrees C tests but not found in 150 degrees C tests. The higher fri ction and wear in 150 degrees C tests as compared to 50 degrees and 10 0 degrees C tests were attributed to the absence of the perfluorocarbo xylate species over the sliding surfaces at high temperatures.