Novel Additives for Passivating Silicon Nitride Bearing Elements in Perfluoropolyalkylether (PFPAE) Lubricants

The U.S. Air Force has a need for stable high performance lubricants for current and next generation gas turbine engines. Perfluoropolyalkylether (PFPAE) fluids have been the subject of intense development over the past 40 years. This work has led to a current generation of lubricant formulations that are highly resistant to degradation in the presence of modern engineering steels. However, the latest trend in bearing technology is the use of the ceramic silicon nitride. Silicon nitride is susceptible to attack by active fluorine compounds that are produced by the high energy chemistry present at the bearing surface. Luna Innovations proposes a novel new additive having high temperature stability allowing operation above 300oC in engine applications. The novel additives are expected to react under pressure to passivate the silicon nitride surface with a protective thin film chemically bonded to the surface. This will impart inertness to reactive fluorine developed in the PFPAE fluid and greatly reduce wear of silicon nitride bearings.