A Bearing metal should possess the following important characteristics :
1. It should have enough compressive strength to possess adequate load carrying capacity.
2. It should have good plasticity to allow for small variations in alignment and fitting.
3. It should have good wear resistance to maintain a specified fit.
4. It should have low coefficient of friction to avoid excessive heating. Some important bearing metals are following :
Babbit metal
It is a white metal containing 85% tin, 10% Sb and 5% Cu. It is used for heavy duty bearings.
Lead alloy
It contains 40% lead and 60% Cu. It may be cast in position or fused as a tin shell to a bronze or steel reinforcing shell outside.
Phosphor bronze
With 10% tin is used for light load low speed bearings. It can be sand and centrifugally cast.
Cadmium alloy
It contains 95% cadmium, 5% silver and a very small amount of iridium. It is used for medium loaded bearings subjected to high temperature.
Cintered metal
Bearings suitable for light and medium loads are made by sintering metallic powders. A popular composition consist of 90% Cu, 10% tin and a small addition of graphite. Cintering is done at 7000 C. Oil retaining bearings can be made through this process.
