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.
Table of Contents
Materials for Sliding Contact Bearings
Commonly used materials for sliding contact bearings are :
- Babbits (white metals)
- Bronze
- 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)
Composition
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%
Advantages
- They have excellent bondability, embeddability, and conformability.
- They are good corrosion-resistant.
Limitations
Low compressive and fatigue strength at temperatures above 80 degrees.
Applications
Bearings with Babbit material are used in light-duty applications.
Bronze
Composition
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%
Advantages
- Bronze material is cheaper as compared with the babbits.
- These are stronger and can withstand higher pressures.
Limitations
Poor conformability and has a tendency to stick the journal surface at high temperatures.
Applications
Bronze is used in applications where temperature, load, speed, etc are considered to be moderate.
Aluminium Alloy
Composition
Al-89.5%, Sn-6.5%, Si-2.5%, Cu-1%, Ni-0.5%
Advantages
They have high thermal conductivity and fatigue strength.
Limitations
They have poor embeddability.
Applications
As this material is having high thermal conductivity, they are used where an adequate amount of lubricant is not provided.
Copper-Lead Alloy
Composition
Cu-60 to 75%, Pb-25 to 40%
Advantages
They have high compressive as well as fatigue strength and can withstand higher temperatures.
Limitations
Embeddability is average and conformability is very poor.
Applications
These materials are used where temperature, speed, and load are higher.
Cast Iron
Composition:
C.I.
Advantages
They have higher compressive strength.
Limitations
They have poor conformability and embeddability.
Applications
Light duty applications are preferred for C.I. material.
Sintered Metal
Composition
Copper-based and Iron-based sintered bearings.
Advantages
As the bearing material is porous, it can absorb 15-30% of lubricating oil.
Limitations
Fatigue strength is poor.
Applications
They are used in machine tools and automobile applications.
Non-metals
A large number of non-metallic materials are used as bearing material. Here we are discussing only important materials used for bearings.
Rubber
Advantages
They have an excellent ability to absorb shocks. Also, they have high embeddability and conformability.
Limitations
They have poor strength and cannot withstand higher temperatures.
Applications
Used in centrifugal pumps, deep-well pumps, and ships.
Plastics
Advantages :
They are high wear-resistant and have a low coefficient of friction. Also, they are having low cost and have a high impact strength.
Limitations
They have poor thermal conductivity and hence can’t be used at temperatures above 90 degrees.
Applications
Used in marine applications.
Carbon Graphite
Advantages
They can withstand higher temperatures up to 650 degrees. This material is self-lubricating, chemically inert.
Applications
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.
Teflon
Advantages
This material can operate without lubricant. They have a low coefficient of friction and are hard.
Limitations
They have poor strength, poor thermal conductivity, and a high coefficient of thermal expansion.
Applications
They are used in light-duty applications.
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