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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

On the torque and wear behavior of selected thin film MOS2 lubricated gimbal bearings

During the thermal vacuum test phase of the GOES 7 spacecraft, the primary scan mirror system exhibited unacceptably high drive friction. The observed friction was found to correlate with small misalignments in the mirror structure and unavoidable loads induced by the vehicle spin. An intensive effort to understand and document the performance of the scan mirror bearing system under these loads is described. This effort involved calculation of the bearing loads and expected friction torque, comparison of the computed values to test data, and verification of the lubrication system performance and limitations under external loads. The study culminated in a successful system launch in February of 1987. The system has operated as predicted since that time.

Bohner, John J.↗
NASA NTRS2018

Performance of MoS2 Coated Gears Exposed to Humid Air During Storage

The purpose of this work was to study the effect of exposure to humid air on the durability of a molybdenum disulfide dry film lubricant applied to spur test gears and subsequently tested in vacuum environment. This study was motivated by the James Webb Space Telescope (JWST) Mission. Some moving mechanical assembles of the JWST have been exposed to humid air during storage as a subassembly and after integration into a higher-level assembly. molybdenum disulfide dry film lubricant was applied to steel spur test gears and subsequently tested in vacuum environment. One-half of the gears had essentially zero time exposure to humid air prior to testing, and the other half were exposed to humid air of 57 percent relative humidity for exposure durations up to 77 days prior to testing. All tests were completed at the same constant torque and speed. On average, the film durability, as measured by the number of pinion revolutions, was shorter for gears exposed to humid air compared to those with zero exposure. For the unexposed gears, the durability ranged from 53,300 to 190,300 pinion revolutions with an average value of 100,200 and a median value of 83,500 revolutions. For the exposed gears, the durability ranged from 21,000 to 84,700 pinion revolutions with an average value of 64,900 and a median value of 68,800 revolutions. Using the unexposed gears as a baseline, the exposure reduced the average durability by 35 percent and the median value of durability by 18 percent. Red-brown coloration was noted on some of the gear teeth that had been exposed to humid air. The colored regions appeared as soon as 17 days after exposure to humid air. SEM inspections showed that at least some of these colored areas included material raised above the surrounding molybdenum disulfide film.

gear↗
NASA NTRS1978

Lubrication and failure mechanisms of molybdenum disulfide films. 2: Effect of substrate roughness

An optical microscope was used to study the lubrication and failure mechanisms of rubbed MoS2 films applied to three substrate surface finishes; polished, sanded, and sandblasted as a function of sliding distance. The lubrication mechanism was the plastic flow of thin films of MoS2 between flat plateaus on the rider and on the metallic substrate. If the substrate was rough, flat plateaus were created during run-in and the MoS2 flowed across them. Wear life was extended by increasing surface roughness since valleys in the roughened substrate served as reservoirs for MoS2 and as deposit sites for wear debris. In moist air the failure mechanism was the transformation of metallic colored MoS2 films to a black, powdery material that was found by X-ray diffraction to be alpha iron, MoO3, and possibly FeMoO3. In dry argon the failure mechanism was the gradual depletion of MoS2 from the contact region by transverse flow, and the wear debris on the track at failure was alpha iron, residual MoS2, and possibly FeS.

Fusaro, R. L.↗
NASA NTRS1980

Effect of Substrate Surface Finish on the Lubrication and Failure Mechanisms of Molybdenum Disulfide Films

An optical microscope was used to study the lubrication and failure mechanisms of rubbed (burnished) MoS2 films applied to three substrate surface finishes - polished, sanded, and sandblasted - as a function of sliding distance. The lubrication mechanism was the plastic flow of thin films of MoS2 between flat plateaus on the rider and on the metallic substrate. If the substrates were rough, flat plateaus were created during 'run in' and the MoS2 flowed across them. Wear life was extended by increasing surface roughness since valleys in the roughened substrate served as reservoirs for MoS2 and a deposit site for wear debris. In moist air, the failure mechanism was the transformation of metallic colored MoS2 films to a black, powdery material that was found by X ray diffraction to consist primarily of alpha iron and MoO3 powders. In dry argon, the failure mechanism was the gradual depletion of the MoS2 film from the contact region by transverse flow. Analysis of the wear debris on the wear track at failure showed it consisted mainly of alpha iron and some residual MoS2. No molybdenum oxides were found.

Fusaro, R. L.↗