In an earlier post, we have discussed the desirable properties of the bearing material they should possess.
In this post, we are going to discuss the materials of the sliding contact bearing with their advantages, drawbacks along with applications.
Commonly used materials for sliding contact bearings are :
- Babbits (white metals)
- Aluminum alloys
- Copper-lead alloy
- Cast iron
- Sintered metal or porous metal
- Non-metallic materials.
Here we will see the composition of each material with its benefits, drawbacks, and applications.
Babbits (white metals)
In this, there are two types. One is Lead-based Babbit and the other is Tin-base babbit.
Lead-Base Babbit: Pb-74%, Sn-10%, Sb-15%, Others-1%
Tin-Base Babbit : Pb-87%, Sn-86%, Sb-7%, Cu-6%
- They have excellent bondability, embeddability, and conformability.
- They are good corrosion-resistant.
Low compressive and fatigue strength at temperatures above 80 degrees.
Bearings with Babbit material are used in light-duty applications.
In this also there are two types. One is gunmetal and the other is phosphor bronze.
Gunmetal : Cu-87%, Sn-10%, Zn-2%, Ni-1%
Phosphor Bronze: Cu-90%, Sn-10%
- Bronze material is cheaper as compared with the babbits.
- These are stronger and can withstand higher pressures.
Poor conformability and has a tendency to stick the journal surface at high temperatures.
Bronze is used in applications where temperature, load, speed, etc are considered to be moderate.
Al-89.5%, Sn-6.5%, Si-2.5%, Cu-1%, Ni-0.5%
They have high thermal conductivity and fatigue strength.
They have poor embeddability.
As this material is having high thermal conductivity, they are used where an adequate amount of lubricant is not provided.
Cu-60 to 75%, Pb-25 to 40%
They have high compressive as well as fatigue strength and can withstand higher temperatures.
Embeddability is average and conformability is very poor.
These materials are used where temperature, speed, and load are higher.
They have higher compressive strength.
They have poor conformability and embeddability.
Light duty applications are preferred for C.I. material.
Copper-based and Iron-based sintered bearings.
As the bearing material is porous, it can absorb 15-30% of lubricating oil.
Fatigue strength is poor.
They are used in machine tools and automobile applications.
A large number of non-metallic materials are used as bearing material. Here we are discussing only important materials used for bearings.
They have an excellent ability to absorb shocks. Also, they have high embeddability and conformability.
They have poor strength and cannot withstand higher temperatures.
Used in centrifugal pumps, deep-well pumps, and ships.
They are high wear-resistant and have a low coefficient of friction. Also, they are having low cost and have a high impact strength.
They have poor thermal conductivity and hence can’t be used at temperatures above 90 degrees.
Used in marine applications.
They can withstand higher temperatures up to 650 degrees. This material is self-lubricating, chemically inert.
Carbon graphite is used in applications where temperatures are too high to permit the use of lubricated bearings. Also used in applications where the use of lubricant is prohibited.
This material can operate without lubricant. They have a low coefficient of friction and are hard.
They have poor strength, poor thermal conductivity, and a high coefficient of thermal expansion.
They are used in light-duty applications.