Vapor Lubrication of Gear and High Velocity Sliding Systems

It is now possible to use fluids beyond the liquid range to lubricate surfaces with thin condensate films that provide complete surface separation with EHD mechanisms. The lubricant, supplied internally or externally as a vapor, eliminates complex hardware associated with recirculating oil systems. The temperature range over which EHD lubrication prevails is significantly extended. Vapor has been demonstrated in rolling element bearings with smooth surfaces and near rolling conditions. The proposed effort is to show the feasibility of vapor lubricated gear surfaces which have high sliding velocities and rough surfces compared to rolling element bearings - a necessary requirement for many advanced propulsion systems. The approach is to develop a tribo-contact system with low traction and excellent run-in characteristics to allow thin film EHD lubrication. The traction of PFPE fluids decreases with temperature (i.e. sliding velocity). With sufficiently high molecular weight PFPE's, EHD films can prevail for long life, reliable lubrication. Surfaces can be run-in topographically with silver or copper coatings which also enhances heat dissipation. Vaporized EP additives shall be used to enhance the boundary lubrication performance of the tribo-contact. The vapor lubricated contact shall be evaluated with the WAM3 test machine which is unique in its ability to simulated gear mesh conditions.