EFFECT OF TEMPERATURE, SUBSTRATE TYPE, ADDITIVE AND HUMIDITY ON THE BOUNDARY LUBRICATION IN A LINEAR PERFLUOROPOLYALKYLETHER FLUID

There is a need to better understand the behavior of perfluoropolyalky lether (PFPAE) fluids under boundary lubrication so that their interac tion with metal surfaces may be modified by additives or by other mean s. In this study, the effects of temperature, substrate steel type, an antiwear additive, and atmospheric humidity on the protective surface film formation in a linear PFPAE fluid were studied. The measured per formance characteristics were coefficient of friction, area of wear sc ar, final surface roughness and rate of surface film formation. The hi gh temperature (150 degrees C) caused higher friction and wear as comp ared to lower temperatures (50 and 100 degrees C). The high friction a nd wear at 150 degrees C was explained by the lack of organic adsorbat e him formation over the sliding surfaces at 150 degrees C. It was pro posed that humidity reduces friction and wear by increasing the rate o f formation of perfluorocarboxylate species over inorganic surface lay ers. A fluorinated tertiary alcohol additive reduced the friction at t he first hour of sliding at 150 degrees C. However, the friction was i ncreased towards the end of the five-hour sliding tests due to the los s of the entire additive by evaporation. The rate of surface film form ation and wear protection was higher on M50 steel than on MSO-NIL stee l because the M50 steel surface reacts more with the PFPAE degradation products. (C) 1997 Elsevier Science S.A.