Molybdenum Disulfide and Its Uses as a Dry Lubricant

Molybdenum disulfide (MoS2) is an inorganic compound that finds extensive application as a dry (solid) lubricant. Since this compound remains largely unaffected by oxygen, high temperatures, magnetic fields, and dilute acids, it is an ideal lubricant for heavy-duty operations. This compound is also non-toxic. MoS2 demonstrates low friction owing to the weak bonding between its layered molecular structures.

This compound is bluish or silver gray in appearance and has a coefficient of friction that ranges between 0.06 COF to 0.15 COF. The appearance and feel of MoS2 is similar to that of graphite. However, MoS2 provides significantly higher lubricating performance than graphite. MoS2 works several times more effectively than graphite even in vacuum environments. While graphite requires an external source of moisture, MoS2 achieves peak performance in the absence of water vapor.

What is a dry film lubricant ?

These lubricants are also referred to as a solid film lubricant or a dry lubricant. As the name implies, this lubricant is used in a solid state. It is different from a liquid lubricant both physically and operationally. Apart from MoS2, materials such as tungsten disulfide and graphite are widely used as dry lubricants. Here are two common scenarios where one might need to opt for dry lubricants:

Certain machines and systems, once installed, have several hard-to-reach areas that cannot be accessed for regular lubrication. Dry lubricants provide long-term reduction in friction and wear in such conditions.

Liquid lubricants often fail in extreme environments exposed to high temperatures, vacuum, or extreme pressure. Dry lubricants such as tungsten disulfide and molybdenum disulfide remain largely unaffected in such environments and continue to provide the desired lubrication performance.

Using molybdenum disulfide as a solid film lubricant

This lubricant can be applied to the desired substrate using several different methods. Some of the most common ways of applying MoS2 low friction coatings to the surface of a substrate are:

Sprayingr
Physical vapor depositionr
Rubbing and burnishingr
Impingement with or without inorganic bindersr
Dipping (carried out using a paint-like substance comprising MoS2)

If applied at ambient temperature, it requires no curing time. There are several standard specifications that determine the application of solid film lubricants. MoS2, for instance, could be applied in accordance with MIL-PRF-46010 and AS5272 and similar to AMS2526.

The performance of MoS2 as a dry film lubricant would depend on external factors such as: humidity levels, sliding conditions of the application, purity of the application, speed of movement and so on.

Applications of molybdenum disulfide

There are a myriad of applications where MoS2 is considered to be a reliable dry lubricant. These include chain saws, pilot valves, engine and drive train parts, compressors, rheostats, cryogenic pumps, slide mechanisms, bearings, gears, fasteners and magnetic heads among many others.