Materials for Sliding Contact Bearing

In earlier post, we have discussed about the desirable properties of the bearing material they should posses.
In this chapter, we will discuss about the materials of the sliding contact bearing with their advantages, drawbacks along with applications.
Commonly used materials for sliding contact bearings are :
  1. Babbits (white metals)
  2. Bronze
  3. Aluminium alloys
  4. Copper-lead alloy
  5. Cast iron
  6. Sintered metal or porous metal
  7. Non-metallic materials.
Here we will see the composition of each material with their benefits, drawbacks and applications.

1. Babbits (white metals):

Composition : In this there are two types. One is Lead-base babbit and 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 : 

1. They have excellent bondability, embeddability and conformability.
2. 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.

2. Bronze :

Composition : In this also there are two types. One is gun metal and other is phosphor bronze.

Gun metal : Cu-87%, Sn-10%, Zn-2%, Ni-1%
Phosphor Bronze: Cu-90%, Sn-10%

Advantages :

1. Bronze material is cheaper as compared with the babbits.
2. These are stronger and can withstand with higher pressures.

Limitations :

Poor conformability and has tendency to stick journal surface at high temperature.

Applications :

Bronze is used in the applications where temperature, load, speed etc are considered to be moderate.

3. 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.

Applicatons :

As this material is having high thermal conductivity, they are used where adequate amount of lubricant is not provided.

4. 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.

5. Cast Iron :

Composition : C.I.

Advantages :

They have higher compressive strength.

Limitations :

They have poor conformability and embeddability.

Applications :

Light duty applications are preffered for C.I. material.

6. 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 poorr.

Applications :

They are used in machine tools and automobile applications.

7. Non-metals :

Large number of non-metallic materials are used as bearing material. Here we are discussing only important materials used for bearings.

(1) Rubber :

Advantages :

They have excellent ability to absorb the shocks. Also they have high embeddability and conformability.

Limitations :

They have poor strength and cannot withstand at higher temperatures.

Applications :

Used in centrifugal pumps, deep-well pumps and in ships.

(2) Plastics :

Advantages :

They are high wear resistant and have low coefficient of friction. Also they are having low cost and have high impact strength.

Limitations :

They have poor thermal conductivity and hence cant be used at the temperatures above 90 degrees.

Applications :

Used in marine applications.

(3) Carbon Graphite :

Advantages :

They can withstand higher temperatures up to 650 degrees. This material is self lubricating, chemically inert.

Applications :

Used in the applications where temperature are too high to permit the use of lubricated bearings. Also used in applications where use of lubricant is prohibited.

(4) Teflon :

Advantages :

This material can operate without lubricant. They have low coefficient of friction and are hard.

Limitations :

They have poor strength, poor thermal conductivity and high coefficient of thermal expansion.

Applications :

They are used in light duty applications.
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Sujit Kadus

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