NASA has an ongoing need for high-temperature solid lubricant coatings to reduce friction and wear in turbine engines, rocket engines, and other mechanical systems. Such lubricants must be thermally and chemically stable in air, vacuum, and reducing environments like hydrogen. Traditional lubricants like oil, grease, and PTFE (Polytetrafluoroethylene), and even more exotic solid lubricants like graphite and molybdenum disulphide, lack such capabilities. The key problem is to identify and formulate a material that possesses good mechanical properties, long-term environmental durability, and acceptable friction and wear-reducing characteristics while being practical to apply to bearings, seals, and other mechanical components.
A new composite material, NASA PS400, has been invented to provide a means to reduce friction and wear in mechanical components while exhibiting excellent dimensional stability and smooth finished surfaces. This plasma sprayed coating is a variant of the previously patented PS304 coating, and has been formulated to provide higher density, smoother surface finish, and better dimensional stability than PS304.
This composite material is typically produced as a coating. The coating can be made by plasma spraying or other suitable technique. PS400 can also be made as a standalone solid composite material through the powder metallurgy technique. It is made by combining its constituents (a nickel-molybdenum binder, chrome oxide hardener, silver lubricant, and barium fluoride/calcium fluoride eutectic lubricant) in powder form, which can then be spray-deposited or made by other means such as powder metallurgy. The resulting composite material is then finished by grinding and polishing to produce a smooth, self-lubricating surface.
In operation, the PS400-covered surface slides against a mating material, typically a metal, superalloy, ceramic, or other high-performance material, reducing friction and wear and resulting in a long-wearing smooth interface. The material provides low friction and wear over a wide temperature range, excellent dimensional stability, smooth finished surfaces, and no requirement to conduct a post-deposition heat treatment prior to service.