Dry bushing is usually plain composite bushes that have to be able to run with marginal or no lubrication. The main requirement of dry sliding bearing is that the bearing surfaces have a low coefficient of friction. Dry bushings include polymer dry bearing such as DU bush and alloy dry bearing.
Dry Bearing has the simplest and most convenient lubrication method. It is specially suited for the following applications:
Coating threads to prevent seizure and enable release
Coating Shafts that 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
Dry Bearings are usually based on Molybdenum Disulphide (MoS2) or Graphite and sometimes are the combination of two. Generally speaking, dry bushing based on MoS2 is used in the lubrication of machines, and graphite based lubricants are used in specialized industries including hot metal working. Other specialty dry lubricants are available including Tungsten Disulphide
Molybdenum Disulphide is a black crystalline solid which shears easily and has a low coefficient of friction. It is resistant to solvents and chemicals and can be used at temperatures up to 250ºC.
Graphite has a thin flat crystalline structure that sticks strongly to metal surfaces and is a good conductor of heat and electricity. Graphite is relatively inert, being 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.
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