Molybdenum disulfide lubricant

Dry lubricants are usually added to the powder in order to decrease the friction effects. The more common lubricants include zinc stearate [557-05-17, lithium stearate [4485-12-5] calcium stearate [1592-23-0] stearic acid [57-11-4] paraffin, graphite, and molybdenum disulfide [1317-33-5]. Lubricants are generally added to the powder in a dry state in amounts of 0.25—1.0 wt % of the metal powder. Some lubricants are added by drying and screening a slurry of powder and lubricant. In some instances, lubricants are appHed in Hquid form to the die wall. 

A small portion of molybdenite concentrate production is purified to yield lubricant-grade molybdenum disulfide, a widely used soHd-state lubricant. 

Titanium disulfide has been proposed as a soHd lubricant. The coefficient of friction between steel surfaces is 0.3, compared to only 0.2 for molybdenum disulfide. However, because it does not adhere strongly to metal surfaces, TiS2 is generally less effective than molybdenum sulfide. 

Tungsten disulfide forms adherent, soft, continuous films on a variety of surfaces and exhibits good lubricating properties similar to molybdenum disulfide and graphite (51) (see also Lubrication and lubricants). Itis also reported to be a semiconductor (qv). 

SoHd lubricants ate added to help control high friction characteristics in high speed or heavy-duty appHcations where high temperatures are generated. Molybdenum disulfide [1317-33-5] M0S2, may be used alone or in a complex compound formed by grinding with fine natural graphite, and zinc sulfide [1314-98-3] ZnS. Other compounds include calcium fluoride, cryoHte [15096-52-3] Na AlF, rare-earth oxides, and metal sulfides, eg, iron, antimony, or zinc (see LUBRICATION AND LUBRICANTS). 

Molybdenum disulfide (M0S2) and tungsten diselenide ( VSe2) are used for their excellent dry lubricant properties. 

Carbon monofluoride has found use as a lubricant. Studies by Fusaro and Sliney FI, F2) and Gisser (G2) showed that carbon monofluoride is superior to molybdenum disulfide under many conditions. Grafting of monomers can further improve lubricity (B4). Electrochemical applications are discussed later. 

Miyake, S., Sekine, Y., Noshiro, J., and Watanabe, S., Low-Friction and Long-Life Solid Lubricant Films Structured of Nanoperiod Tungsten Disulfide and Molybdenum Disulfide Multilayer, Jpn. J. Appl. Rhys., Vol. 43, 2004, pp. 4338-4343. 

Molilat Lubricity additive containing molybdenum disulfide for improved resistance to wear, pitting and fretting. Reduces noise, increases maximum speed and engine life and cuts fuel consumption. 

Molybdenum disulfide occurs in nature as mineral molybdenite. It is the principal ore from which molybdenum metal is recovered commercially. The compound is used as a dry lubricant and as an additive to lubricant. It also is used as a catalyst. 

In tests of materials saturated with liq oxygen and subjected to 71-75 lb drop weight tests, the following were found acceptable (one de-tonation/40 impacts or none/20) fluorocarbon oils greases, graphite, halogenated biphenyl molybdenum disulfide lubricants, polyethylene... 

Tests showed that liquid lubricants do not even provide adequate lubrication in the lower Vacuums of space simulators. Solid lubricants, such as molybdenum disulfide, tungsten disulfide. and the soft metals have given better results. However, the known data about space lubricants are results of simulator measurements made in the pressure range of 10 s to 1C6 torr which does not simulate real space conditions, and therefore, these available data cannot be considered completely valid. It can be expected that definite data on lubricant performance in a vacuum will be obtained by conducting tests in a simulator that reaches the low 10"10 torr range. At this press level, the monolayer formation time is increased to at least several hours which will result in a sufficient time span for observing the metal... 

Molybdenum disulfide also forms sheet molecules. It consists of covalently bonded sheets with sulfur atoms on both sides of molybdenum atoms, as shown in Figure 17.4. These sheets are only weakly bonded. The ability of these sheets to slide over each other explains the lubricity of M02S, which is used as a high-pressure solid lubricant in metal working. 

As the coefficient of friction can be reduced by the use of a lubricant, it is generally beneficial to use a suitable oil or grease when required. The addition of a modifier to the prepolymer itself must be done with care, as the material will reduce the overall properties including aging and may influence the bond ability of the material. Additives that have been employed in this application include molybdenum disulfide, graphite, and silicone oil. They must be used at the lowest level possible. 

Molybdenum disulfide is dispersed in greases and oils for lubrication in volatile carriers it is used to form dry coatings of lubricant. Sodium molybdate is an especially effective corrosion inhibitor on aluminum surfaces and is dissolved in cooling solutions to protect aluminum motor blocks in automobiles. 

Bullet jacket materials include gilding metal cupronickel cupronickel-coated steel nickel zinc-, chromium-, or copper-coated steel lacquered steel brass nickel- or chromium-plated brass copper bronze aluminum/alumi-num alloy Nylon (Nyclad), Teflon- and cadmium-coated steel (rare). Black Talon bullets have a black molybdenum disulfide coating over the metal bullet jacket which acts as a dry lubricant. Steel jackets are frequently coated both inside and outside as an anticorrosion measure. Gilding metal is by far the most common bullet jacket material. Tin is claimed to have lubricating properties and is sometimes incorporated in bullet jacket material. The alloy is known as Lubaloy or Nobaloy and contains 90% copper, 8% zinc, and 2% tin. 

Bullet lubricants frequently contain mixtures of some of the following beeswax, petroleum jelly, sheep tallow, carnauba wax, molybdenum disulfide, lithium base grease, ceresin wax, powdered graphite, paraffin wax, Alox compound, and Zokorite. The mixture may be dissolved or suspended in a fast-drying solvent or applied directly while hot. 

Lubricating products range from light mineral oil to dry lubricants incorporating molybdenum disulfide, fluorocarbons (PTFE), and other synthetic lubricants. 

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