The surface chemistry of organic lubricants for vapor phase lubrication

A study of the chemistry of vapor phase lubricants on several surfaces was performed in ultrahigh vacuum (UHV) using a variety of surface analytical techniques. Vapor phase lubrication has been proposed as a mechanism for the lubrication of high performance gas turbine engines operating at temperatures in excess of those amenable to liquid lubrication. In this method, a vapor lubricant is continuously delivered by a carrier gas to hot engine components and reacts on their surfaces to deposit a thin, solid, lubricating film which protects the engine surfaces from sliding wear. The most widely studied vapor phase lubricants are phosphorus containing organics, including aryl phosphates such as tricresylphosphate (TCP), (CH3-C 6H4O)3P=O. These phosphates are thought to function by decomposing on reactive metal surfaces, such as Fe and Cu, to form polyphosphate films which contain small graphitic particles. The resulting carbon/phosphorus film provides the effective lubrication.; While TCP serves as a good vapor phase lubricant on Fe and Cu surfaces, it has been shown that Ni surfaces are not well lubricated by TCP vapors. The surface chemistry of m-TCP on clean and phosphorous passivated Ni(100) surfaces was studied in order to understand this issue. m -TCP decomposes on clean Ni(100) surface upon heating to 800 K to deposit carbon and phosphorous on the surface with the evolution of H 2, CO, benzene, and toluene. This indicates that Ni substrate is active toward TCP decomposition to induce lubricous film formation. By further heating to 1000 K, all the surface carbon dissolves into the Ni bulk and only phosphorous is left on the surface. It suggests that the surface chemistry of TCP by itself cannot explain the fact that lubricating films do not form by decomposition of TCP vapor on Ni surfaces.; The surface chemistry of m-TCP on the clean and Fe-modified SiC surfaces was studied in order to explore the development of a method for vapor lubrication of ceramic materials. Although ceramics such as SiC are desirable materials for high temperature applications, their surfaces are unreactive for the decomposition of TCP and thus not amenable to vapor phase lubrication. As a means of activating the SiC surface for TCP decomposition we have used chemical vapor deposition of Fe from Fe(CO)5. (Abstract shortened by UMI.)...