In order to achieve the technology and life cycle goals targets for the advanced turbine engines operating between -60 deg and 1500 deg f. Solid lubricants offer a viable approach. Durability limitations for such engines result from high operating temperatures and the elimination of cooling systems. These factors minimize the effectiveness of conventional oil or grease lubricant due to thermal and oxidation degradation. Most of the conventional solid lubricants, such as molybdenum sulfide, graphite, lead oxide, etc., either possess lower than the desired temperature limit or provide lubricant for a narrow temperature range. A key element for achieving the desired friction and wear properties used under severe operating conditions is to identify a solid lubricant which can exhibit outstanding thermal and oxidation stabilities, show good response to ceramics and high temperature alloys over a broad temperature range, and provide good lubricating properties between -60 deg and 1500 deg f. A class of emerging complex sulfur-containing compounds (e.g., oxythiomolybdates) is among the prime candidates. To further enhance the oxidation stability of the identified solid lubricants and to improve durability for prolonged usage in a recirculating powder delivery system, microencapsulation of the solid lubricant with a suitable, high temperature inorganic composition will be investigated.
