Tribology of Advanced Materials for Extreme Conditions Including Space Applications
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Date
2023-08-03
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Abstract
Extreme conditions dictate the utilization of advanced materials and the development of state-of-the-art processes to accommodate the strong needs of low friction and wear in several bearing applications. Such extreme conditions can be found in the Venusian atmosphere, nuclear reactors, and superlubricity applications. Due to the variety of conditions of each application, different approaches were taken to address these challenges.
NASA and other space agencies seek to explore the harsh atmosphere and surface of Venus by deploying balloons, rovers, and drills to exploit information of the atmospheric composition and the soil and. To this end, a systematic study was carried out with the selection, testing, and characterization of advanced coatings, including a plasma sprayed (PS) NASA-developed nickel-based alloy, namely PS400. It was found that diamond-like carbon (DLC) coating significantly enhanced the tribological properties of PS400 at room temperature conditions (RT). Also, the main lubricating mechanism of PS400 is due to the generation of oxide glazes when subjected to high temperature (HT) oxidative environments. However, under Venusian environment the wear performance degrades. Furthermore, DLC and titanium-doped molybdenum disulfide (TiMoS2) can be used as sacrificial coatings when paired with PS400 for lower temperatures (i.e., during descending on Venusian surface), and initial operation. Another significant finding is that DLC and TiMoS2 depicted extreme chemical inertness when exposed to Venusian-simulated atmosphere for 72 hours, whereas PS400 and polycrystalline diamond (PCD) formed dense adsorbed layers rich in sulfur. Also, the mechanical properties of PCD remained unaffected following Venusian aging, therefore, can be used as a structural material where dimensional precision is of a concern. Finally, the sulfur-rich layer appeared to have good lubrication properties when subjected to HT sliding.
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Tribology, high temperature materials, Venus, advanced polymers, phase-change materials, superlubricity, laser-peening, nuclear reactors