Roymech engineering encyclopedia

Solid and Dry Lubrication Systems and Materials




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Dry lubrication uses solid materials to reduce friction and wear without the need for oils or greases. Common dry lubricants include molybdenum disulphide, graphite, and specialised polymer materials. These systems are particularly useful in high load, low speed, or extreme temperature environments where conventional lubrication is unsuitable.

Dry lubrication uses solid materials such as molybdenum disulphide (MoS2) and graphite to reduce friction without liquid lubricants. It is commonly used in high load, low speed, and extreme temperature applications.

Dry Lubrication - Bearings

Dry Lubrication is the simplest most convenient method of lubrication. However any bearing surfaces based on dry lubrication will progressively wear during relative movement

Dry lubrication is ideally suited for the following applications;
  • Coating threads to prevent seizure and enable release

  • Coating Shafts which are a tight fit in holes, to prevent fretting and binding, and to aid release

  • As a lubricant between surfaces subject to high loads and slow relative movement

Solid /Dry Lubricants

Dry Lubricants are generally based on Molybdenum Disulphide (MoS2) or Graphite and sometimes combination of the two. Generally lubricants based on MoS2 are used in the lubrication of machines and graphite based lubricants are used in specialised industries including hot metal working. Other speciality dry lubricants are available including Tungsten Disulphide. (Ref ws2 Link below.)

Molybdenum Disulphide

MoS2 is a black crystalline solid which shears easily and has a low coefficient of friction . It is resistant to solvents chemicals and can be used at temperatures up to 250 0 C.

Graphite

Graphite has a thin flat crystalline structure which adheres strongly to metal surfaces and is a good conductor of heat and electricity. Graphite is relatively inert unaffected by acids, alkalis and solvents. As a lubricant it enables metal surfaces to resist seizure even at very high loads. However it results in more surface wear than MoS2. It is therefore used less for lubrication of metal surfaces than MoS2.

Dry rubbing bearings (Plastic Based)

These are usually plain plastic bushes which have to be able to run with marginal or no lubrication. The main requirement of dry bearings is that the bearing surfaces have a low coefficient of friction. These bearings are used in undemanding applications such as low speed moving parts in domestic appliances, instrument and electro-mechanical devices.



Bearing Materials

  • nylon

  • acetal copolymer

  • ptfe

Thermoplastic bearing materials are often filled with glass, carbon, bronze, lead. These bearings usually consist of a thin layer of bearing material bonded onto a metal backing. Bearings such as SKF GLYCODUR F and Glacier DU consist of a steel backing and a sintered bronze layer. The porous bronze is filled with ptfe and other friction reducing additives.


Applications of Dry Lubrication

  • Thread coatings to prevent seizure and galling
  • Shafts and tight fits to prevent fretting and binding
  • High load, low speed sliding surfaces
  • Extreme temperature environments where oils fail
  • Maintenance-free or inaccessible components

Advantages of Dry Lubrication

  • No need for liquid lubricants
  • Suitable for extreme temperatures
  • Resistant to chemicals and contaminants
  • Reduces risk of leakage and contamination
  • Effective under high loads and slow movement

Disadvantages of Dry Lubrication

  • Higher wear rates compared to fluid lubrication
  • Limited effectiveness at high speeds
  • Shorter service life in some applications
  • May require reapplication or replacement
  • Lower heat dissipation than oil-based systems

Frequently Asked Questions

What is dry lubrication?

Dry lubrication uses solid materials such as MoS2 or graphite to reduce friction without the use of oils or greases.

Where is dry lubrication used?

It is used in high load, low speed, or extreme temperature environments where conventional lubrication is unsuitable.

What are common dry lubricants?

Common materials include molybdenum disulphide (MoS2), graphite, and PTFE-based compounds.

Are dry lubricants better than oils?

Dry lubricants are better in extreme conditions, but oils and greases generally provide better performance in high-speed applications.



See Also


Links to Solid/Dry Lubrication and Bearings
  1. Wikipedia-Notes..Dry Lubrication Notes
  2. Dicronite Dry Lubrication..high technology dry lubrication systems
  3. Molyslip ..Molyslip Lubrication - Product and technical information
  4. Dow Corning ..MolyKote lubricatant literature download
  5. ws2 ...Tungsten Disulphide Information