Lithium Base Grease High Temperature Resistance Performance Upgrade Strategy

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Category: Tungsten Information
Published on Tuesday, 07 November 2017 16:09
Lithium base grease has many excellent properties after adding a variety of additives. It is widely recognized as a versatile and long-life grease.
 
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With the use of large quantities of high temperature, heavy load and high speed machinery in modern industry, multi-effect grease with excellent high temperature and extreme pressure is required. Extreme pressure composite lithium base grease based on composite lithium base grease, complete by adding extreme pressure additive, the most commonly used additive is tungsten disulfide and molybdenum disulfide.
 
Lithium molybdenum disulfide base grease is widely used in the lubrication of heavy duty gears and bearings, such as steel rolling machines, mining machinery, heavy lifting machinery, etc. Molybdenum disulfide can maintain low friction performance in vacuum and high temperature, but the ability of molybdenum disulfide attached to metal surface is lower than that at normal temperature. In addition, the natural molybdenite often contains the associated gangue, so its purity is difficult to improve, so it is easy to mix impurities when molybdenum disulfide used as a lubricant. When 0.5% of SiO2 is mixed with molybdenum disulfide, although the friction coefficient increases a little,  the abrasion increases obviously. In the aerospace industry and other fields, the performance of the least bit of difference, there may be a lot of results, so we need to upgrade molybdenum disulfide lubricant.
 
Tungsten and molybdenum have similar physical properties, but tungsten has better high-temperature resistance and physical and chemical stability than molybdenum, therefore, tungsten disulfide used as a lubricant to lithium base grease can produce better lubrication effect than mos2.
 
Tungsten disulfide lithium based grease can be regarded as upgraded version of molybdenum disulfide lithium based grease. Molybdenum disulfide is prepared from natural molybdenite by flotation process, tungsten disulfide can only be prepared by chemical method, the production cost is 3 times of molybdenum disulfide. Tungsten disulfide as a new lubricating material, usually is not only applicable to the lubrication conditions, but also can be used in a high temperature and high pressure, high vacuum, high load, radiation and work environment in the harsh corrosive medium.
 
Tungsten disulfide is insoluble in water, oil, alcohol, grease and other organic solvents, Except for the strong oxidation of nitric acid, hydrofluoric acid, nitric acid and hydrochloric acid mixed acid, the general acid and alkali solution is insoluble, the decomposition temperature in the atmosphere is 510°C, the oxidation rate is rapid at 539°C, and it can be lubricated for a long time under 425°C. The vacuum can be stabilized to 1150°C.
 
The friction factor in the atmosphere is 0.03, the extreme pressure strength is 21.00M Pa, and the radiation resistance is also stronger than that of graphite and molybdenum disulfide. Therefore, lithium tungsten sulfide based grease is the best lubricant material.
 

 

 

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