Improved Additives for Perfluoropolyalkylether (PFPAE) Lubricants with Silicon Nitride Rolling Elements

Hybrid bearings utilizing silicon nitride rolling elements in conjunction with steel inner and outer bearing races are being developed for use in gas turbine engines. Due to their outstanding thermal and oxidative stability, perfluoropolyalkylether (PFPAE) fluids are of interest as potential high temperature liquid lubricants in these systems. However, this same unique chemistry that provides their higher stabilities also creates some potential problems. One of these is the lack of compatibility with silicon nitride materials. Similar incompatibilities of the PFPAE-based lubricants with conventional bearing metals have been successfully addressed by PFPAE base oils coupled with soluble performance-enhancing additives developed by the U.S. Air Force that improve the compatibility at high temperature. However these materials are not effective with silicon nitride. Under the proposed program, METSS will develop a new improved class of PFPAE lubricants designed for better compatibility with hybrid bearing materials by a combination of PFPAE base oils with maximized stabilities coupled with new, soluble performance-improving additives that significantly improve the compatibility of these lubricants with silicon nitride at high temperature. The proposed program will also address additional issues related to material compatibility issues, personnel safety, environmental impact and use costs.