A pin-on-disk tribometer was used to study the coefficient of fiictio~z (1s (L filnction of temperature for tricresylphosphate (TCP) on C V M M -5 0 tool steel under the following conditions: T C P was present i n (L liquid reservoir (bulk lubrication), and T C P was applied cw. a liquid layer directly to the disk (limited lubrication). Under limited lubrication conditions, experiments were performed i n dry ( < 100 ppm H20) air, dry ( C 20 ppm H20) nitrogen, clry nitrogela zoith tlre disks heated to 700°C, then cooled to room temperu1~1,rc before the T C P was applied and the measurements made (/)reheated disks), and moist nitrogen using preheated disks. The coefficient of friction decreased at a characleristic temperature, T,.'I',. values obse~ved were: 265OC for bulk lubrication conditions i n dly air, 225OC for limited lubrication conditions i n dry air, and 215°C for limited lzibrication conditions i n dry nitrogen. The w e of preheated disks produced a sharp failure temperature at 2 1 8°C rohich was taken as the temperature about which the behavior of T C P should be judged. X-ray photoelectron spectroscopy confirmed tlre presence of phosphate on the surface of TCP-lubricated iron pins. Depth profile studies support the suggestion that a chemical reaction occurs between the T C P and the metal surjkce at T,.
N a t i o n a l A e r o n a u t i c s and Space A d m i n i s t r a t i o nLewis Research Center C l e v e l a n d , O h i o 44135
SUMMARYThe r e a c t i o n s o f l i n e a r p e r f l u o r o p o l y a l k y l e t h e r (PFAE) l u b r i c a n t s w i t h a-FezO3 and Fe203-based s o l i d s u p e r a c i d s were s t u d i e d .
a-Fe2O3 proceeds i n two s t a g e s . The first s t a g e i s an i n i t i a l slow c a t a l y t i c d e c o m p o s i t i o n o f t h e f l u i d . T h i s r e a c t i o n r e l e a s e s r e a c t i v e gaseous p r o d u c t s which a t t a c k t h e m e t a l o x i d e and c o n v e r t i t t o FeF3. more r a p i d d e c o m p o s i t i o n o f t h e f l u i d , e f f e c t e d b y t h e s u r f a c e FeF3. A s t u d y of t h e i n i t i a l breakdown s t e p was p e r f o r m e d u s i n g a-Fe203, a-FezO3 p r e c o n v e r t e dt h e breakdown r e a c t i o n i n v o l v e s a c i d i c a t t a c k a t f l u o r i n e atoms on a c e t a l carbons i n t h e l i n e a r PFAE. P o s s i b l e approaches t o combat t h e p r o b l e m a r e o u t 1 i ned .The r e a c t i o n w i t hThe second s t a g e i s a
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