Interaction of Polyol Esters and Phosphate Esters with Metal Carbides

Abstract

The need for higher performance in jet turbine engines has led to the development of alloys with greater hardness for use in bearings. The increased hardness is a result of carburizing of the surface which leads to a change in the surface chemistry through the formation of metal carbides. The authors have found that metal carbides react differently with the lubricants and additives than the oxides found on the surface of currently used alloys. Of particular concern is the observed reaction of the ester basestock with metal carbides in the presence of phosphate esters. The authors have found that metal carbides can catalyze the decomposition of hindered esters in the presence of aryl phosphates to give the component acids. Products of the reaction include free acids, phenyl esters, and dehydrogenated esters. This reaction is expected to rapidly degrade the performance of the oil due to both acid formation and viscosity breakdown. Examination of the remaining solid material indicates that phosphorus has been incorporated into the structure, presumable as phosphate.