“Bearing is a mechanical element which locates two machine parts relative to each other and permits relative motion between them.”
For the bearings to be effective, they should have the following desirable properties :
- Compressive strength
- Fatigue strength
- Corrosion resistance
- Thermal conductivity
- Cost and availability
Compressive Strength: The max pressure that is acting on the bearing is greater than the average pressure. Hence in order to withstand this maximum pressure, the bearing material should have high compressive strength.
Fatigue strength: In some applications, the bearings are subjected to high fluctuating loads. So to avoid fatigue failure, the bearing material should have sufficient endurance strength.
Bondability: It is the ability of the material to form a strong bond with other materials. Generally strong bonds are formed with steel. High capacity bearings are made by one or more thin layers of bearing material with high strength steel.
Corrosion resistance: In the applications where there is high working temperature, this temperature oxidizes the lubricating oil and forms the corrosive acids. This formed acid attacks on bearing material and corrodes it. So corrosion resistance property is also important in case of bearing material.
Conformability: It is the ability of the bearing material to yield and adapt its shape to that of the journal.
Embeddability: It is the ability of the bearing material to embed small particles of dust, dirt or abrasive particles without scoring the journal. The dirt or dust particles in the lubricating oil may cause the jamming in the clearance space. Hence the bearing material should have embeddability characteristics.
Thermal Conductivity: For the rapid dissipation of the heat, bearing material should have high thermal conductivity.
Cost and Availability: The bearing material should have low cost and also it should be easily available in the market for its production.
Commonly used materials for the bearings are :
- Babbits (white metals)
- Copper-lead alloy
- Cast iron
- Aluminum alloy
- Sintered metal or porous metal
- Non-metallic materials.
These materials are discussed in brief in Materials for Sliding Contact Bearings.