NASA Technical Reports Server NTRS 20150023048: Tribological Evaluation of Candidate Gear Materials Operating Under Light Loads in Highly Humid ConditionsReportar como inadecuado



 NASA Technical Reports Server NTRS 20150023048: Tribological Evaluation of Candidate Gear Materials Operating Under Light Loads in Highly Humid Conditions


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A series of pin-on-disk sliding wear tests were undertaken to identify candidate materials for a pair of lightly loaded timing gears operating under highly humid conditions. The target application involves water purification and thus precludes the use of oil, grease and potentially toxic solid lubricants. The baseline sliding pair is austenitic stainless steel operating against a carbon filled polyimide. The test load and sliding speed 4.9 N, 2.7 m-s were chosen to represent average contact conditions of the meshing gear teeth. In addition to the baseline materials, the hard superelastic NiTiNOL 60 60NiTi was slid against itself, against the baseline polyimide, and against 60NiTi onto which a commercially deposited dry film lubricant DFL was applied. The alternate materials were evaluated as potential replacements to achieve a longer wear life and improved dimensional stability for the timing gear application. An attempt was also made to provide solid lubrication to self-mated 60NiTi by rubbing the polyimide against the disk wear track outside the primary 60NiTi-60NiTi contact, a method named stick or transfer-film lubrication. The selected test conditions gave repeatable friction and wear data and smooth sliding surfaces for the baseline materials similar to those in the target application. Friction and wear for self-mated stainless steel were high and erratic. Self-mated 60NiTi gave acceptably low friction approx. 0.2 and modest wear but the sliding surfaces were rough and potentially unsuitable for the gear application. Tests in which 60NiTi pins were slid against DFL coated 60NiTi and DFL coated stainless steel gave low friction and long wear life. The use of stick lubrication via the secondary polyimide pin provided effective transfer film lubrication to self-mated 60NiTi tribological specimens. Using this approach, friction levels were equal or lower than the baseline polyimide-stainless combination and wear was higher but within data scatter observed in these preliminary tests. Based upon these results, self-mated 60NiTi gear teeth utilizing solid lubrication, is a reasonable approach for the target application.



Autor: NASA Technical Reports Server (NTRS)

Fuente: https://archive.org/







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