Four research areas at the NASA Glenn Research Center involving the tribology of space mechanisms are highlighted.These areas include: soluble boundary lubrication additives for perfluoropolyether liquid lubricants, a Pennzane dewetting phenomenon, the effect of ODC-free bearing cleaning processes on bearing lifetimes and the development of a new class of liquid lubricants based on silahydrocarbons.
The effects of nitrogen implantation conditions (ion energy, dose rate, and processing time) on the thickness and wear behavior of N-rich layers produced on 304 stainless-steel surfaces are examined. Surfaces implanted at elevated temperatures ( ~400°C) with 0.4 to 2 keV nitrogen ions at high dose rates (1.5 to 3.8 mA/cm 2 ) are compared to surfaces implanted at higher energies (30 to 60 keV) and lower current densities (0.1 to 0.25 mA/cm 2 ). The most wear-resistant surfaces are observed when the implanted-ion energy is near 1 keV and the dose is very large (>2xl0 19 ions/cm ). Typically, surfaces implanted under these optimum conditions exhibit load-bearing capabilities at least 1000 times that of the untreated material. Some comparisons are also made to surfaces processed using conventional plasma-nitriding. Samples treated using either process have wear-resistant surface layers in which the nitrogen is in solid solution in the fee phase. It is argued that the deep N migration ( >l\x,m) that occurs under low-energy implantation conditions is due to thermal diffusion that is enhanced by a mechanism other than radiationinduced vacancy production.
Research on the boundary lubrication performance of two perfluoropolyether (PFPE) thin films in the presence of passirated 440C stainless steel is presented. The study used a standard ball‐on‐disc (BoD) tribometer operating in dry nitrogen and a vacuum spiral orbit tribometer (SOT). Stainless steel surfaces were passivated using one of four techniques: a high‐temperature and low‐temperature chromic acid bath, a tricresyl phosphate (TCP) soak, or UV/ozone treatment for 15 min. After passivation, each BoD disc had a 400 Å film of Krytox® 16256 (PFPE) applied to it. The lives of these films were quantified by measuring the number of sliding cycles before an increase in friction occurred. The lubricated life of the 440C couple was not altered as a result of the various passivation techniques. The resulting surface chemistry of each passivation technique was examined using X‐ray photoelectron spectroscopy. The SOT was used to examine the effects of the TCP treatment on the lubricated life of another PFPE, Brayco® 815Z, under rolling conditions. None of the passivation techniques were found to increase dramatically the oxide film thickness or lubricated life.
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