Enhanced performance of Pennzane (R) greases for space applications by both additive formulations and smooth hard coatings

Tribological requirements of the moving mechanical assemblies (MMAs) of spa cecraft are usually satisfied by a variety of lubricants and materials. Whe n the lubricant elastohydrodynamic film is broken, metal-to-metal contact o ccurs in the MMAs. This may lead to lubricant overheating, and breakdown, a nd then to increased wear and,failure. Wear related failure can also occur due to evaporation and/or creep of the lubricant over the lifetime of space assembly. As requirements for spacecraft performance and lif?,time increas e, improved lubrication systems for MMAs are needed. A considerable amount of progress has been made in developing improved lubricants with advanced a dditives; however their performance has not been evaluated and ranked. In t he present work, four-ball and reciprocating tribometer tests were conducte d to evaluate and rank the performance of various Pennzane (R) based grease s. Employing the reciprocating tribometer technique, Pennzane (R) based gre ases were also evaluated with hard coatings such as titanium nitride (TiN) and titanium carbonitride (TiCN) in a metal-on-coating configuration. Viabi lity of a filtered cathodic arc technique for obtaining very smooth, hard c oatings is demonstrated, The importance of coating deposition temperature f or certain bearing steel materials is also discussed. It is demonstrated th at wear is substantially reduced with an optimized Pennzane (R) grease form ulation on a smooth, hard TiCN surface coating.