Vapor phrue lzcbricalion has been denzonslrc~led tising a conuenlionul fozcr-ball wear Lester ~n , z (11 3 70°C zuing M50 hot hardtzess sleel ball beari~tzgs. The foztr-ball wear tester zucu ~nodtjied lo conhol bolh lhe le~nperalzcre and the enuironnzenl szcrrorcnding the ball pol (~tld spindle. The lzcbricanl i n all cases comprised a hon~ogeneozis gris phrue ntixlure of nilrogen and phosphate ester vapors. The two phosphate eslers zued were lribzclyl phosphnle ( T B P ) and lricresyl pirosphale (TCP). The volzcme percent phosphate ester vapor i n nifrogen rc~nged from 0.1 0 to 6.0 percent. The mini?nzcm lemper-(clzcre of lhe fozlr balls was nzaintained a1 370°C which wcu always nl least 50°C higher than the tenlper(~1zo.e of lhe homoge~zeozls uupors delivered so lhal lhere zuus no possibilily of uapor condensalion on the wear co?~lncts. Vupor phrue lzcb~z'caliotz by pllosphnle esters appears to be as effective at (L bulk letnperature of 370°C us lypical nonaddilive n~i~reral oils w e i,a lhe liquid slate a1 roo~n lerr~peratzere lo 75OC. For exa~r~ple, 7%P delivered fiotn the vapor phase cozcld szipporl loads zcp lo 5 0 kg (~t a 1~6,-icccnl concentrcclimt of only 0.5 percent. Scanni?~g eleclrotz microscopic (SEIM) pictzires of a sleel su~jace (1.1 600°C delivered zuith 1.2 percenl T B P i n a nilrogetz ~(~r r i e r gas show large an~olphozcz like slntclzires. This suggests that the deposited lubricali~zg film exists (LS a polymer of the original T B P it1 a lir/zcidlike stale a / lhis lemperalure. 0 1 1 cooli~zg to roo~n te~n-perulzire, seclio,u of the film apparenlly corclesced giving h e coaling obseroed. Szcchjztidity of h e lzcb~icali?~gfilm at high temperalzcres ruozcld be parlic~tlarly valzic~ble in metal-for~ni~~g operalio~u.

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A kinetic model has been proposed for high-temperature oxidative degradation of lubricants under boundary lubrication conditions. This model incorporates primary oxidation reactions as well as subsequent condensation polymerization reactions that result in viscosity increase and sludge formation. Evaporation of the oil and its volatile primary oxidation products has also been considered. The model has been examined by conducting oxidation and evaporation studies on a commonly used neopentyl polyol ester, trimethylolpropane trlheptanoate, in the Penn State microoxidation test. This thin-film laboratory test simulates lubricant behavior in bearings under elastohydrodynamic and boundary lubrication conditions. The kinetic rate constants for the primary oxidation and the subsequent polymerization reactions have been determined. The rates of reaction appear to be first order. This information coupled with evaporation rates has been used to examine the ability of the model to correctly predict the oxidative behavior of the lubricant. Klaus, , 1983 suggests that the primary reaction is associated with the C-C chain and not the heteroatoms in these molecules.This study treats the oxidation of a polyolester, trimethylolpropane triheptanoate (TMPTH), as a simple reaction with no oxygen diffusion limitations. The basic data are used to model the primary oxidation reaction and subsequent reactions, thereby providing a relationship that can be used to predict the behavior of lubricants given the 0196-4321/86/1225-0596S01.50/0 environments in which they function.