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Lubricating Properties Of Molybdenum Disulfide

wallpapers Industry 2020-06-16

Molybdenum disulfide-natural or synthetic molybdenite ore, with advantages that are difficult to compare with lubricating grease and other solid lubricants, is widely known as "the king of solid lubrication."

As a lubricant, two conditions are necessary: the material has an excellent sliding surface, and the content has strong adhesion to the substrate.

Molybdenum disulfide is superimposed on the S-Mo-S sandwich. Within the layer, S-Mo is closely connected with polar bonds. Between the layers, the S-S are connected by molecular bonds, and the van der Waals-London force bonding force is too weak, and when small shear stress is applied, it can break and produce slip. There is one slip surface between every two sandwich layers. That is, there are 399 suitable slip surfaces in a thin layer of 1μM molybdenum disulfide.

Molybdenum disulfide firmly adheres to the substrate, making it difficult for other lubricants, such as graphite.

Besides, it also has many excellent lubricating properties.

(1) Wide temperature range: high-temperature aviation silicone oil can withstand 250℃ high temperature, and refrigerating machine oil can withstand -45℃ low heat, which is already a good one among lubricating greases. The application of molybdenum disulfide in the air can be used for a long time at 349℃ or short-term use at 399℃; in a vacuum, molybdenum disulfide can work at 1093℃; in an inert gas such as argon, molybdenum disulfide can be Work at 1427°C. In addition to working at high temperatures, molybdenum disulfide powder can also work at -184°C or lower.

(2) Resistant to heavy load: under a heavy-duty, the grease lubricating film will be thinned or even disappeared, and the lubrication will fail. However, the molybdenum disulfide lubricating film with a thickness of only 2.5 μm has excellent lubricating performance under a heavy load of 2800 MPa, 40 m/s, and high speed. Even if the amount is increased to 3200MPa to exceed the yield strength of steel, the lubrication performance of molybdenum disulfide still exists. This isn't easy to achieve with any other liquid and solid lubricants. Therefore, most of the molybdenum disulfide produced in the world is used as a "polar additive" in combination with fats and oils, such as the universal lithium molybdenum disulfide grease, molybdenum calcium disulfide grease, and various molybdenum disulfide gears—film-forming paste and so on.

(3) Vacuum resistance: The spacecraft is flying at the height of more than 500km, and the vacuum of space has reached 1.3×10-2μPa or more: At this time, the evaporation of grease lubricant has exceeded its limit evaporation rate. This will make the lubrication invalid, and the volatile gas will pollute the instrument and the environment, and the lubrication performance of graphite lubricant in the vacuum will be significantly reduced the lubrication performance of molybdenum disulfide under vacuum conditions is better than that in air. The production is even better. Under the vacuum degree of 1.3×10-2μPa, the friction coefficient of the molybdenum disulfide wiping coating film drops to 0.0016, which is much lower than 0.1 in air. Molybdenum disulfide sputtered film bearings working under 1.3μPa vacuum, 8000r/min, 0.2MPa, its working life has exceeded 1500h.

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