Advantage and disadvantage of bearing material in tribology
Answers
BEARING MATERIALS
Introduction :- Powder Matellurgy may be defined as ." the process of manufacturing components from metal powder by compacting and sintering Sintered-metal self-lubricating bearings, produced by Powder Metallurgy route are a unique P/M product and one of the large volume products made by P/M. They are economical, suitable for high-production rates and can be manufactured to precision tolerances. Sintered-metal self- lubricating bearings are widely used in home appliances, small motors, machine tools, aircraft and automobiles business machines, farm and construction equipment.
A brief history Self-lubricating bearings were the first PM components to be mass-produced. Since their introduction, in the beginning of the 1920's , they represent by far the highest volume part output of in PM industry: every year billions of oil-impregnated PM bearings find their applications in mechanical and electromechanical devices, where sliding processes, especially rotary motions, are occurring There are three types of self-lubricating plain bearings used today. Oil-filled sintered bronze bearings were first conceived in the 1930s, with self-lubricating metal-polymer bearings developed around 1950 and lubrication-free solid polymer bearings appearing in the 1960s.
BEARING MATERIALS
Advantages and disadvantages
self-lubricating sintered bearing is a metallic component with high porosity ( 20-25 % in volume ) , impregnated in a lubricant oil. The oil contained in the porosity provides a constant lubrication between bearing and shaft, so the system does not need any additional external lubricant. Self-lubrication allows this type of sliding bearing to work under hydrodynamic conditions, resulting in a very low friction coefficient.
Self-lubricating sintered bearings have some advantages compared to other types of dry sliding bearings: Reliability. The constant oil presence eliminates the risk of seizure, and allows the bearing to work during thousands of hours without wear. Economy. Maintenance-free, no need for lubricants. - Performance. Able to work under loads of up to 10 MPa, and speeds up to 5 m/s. The maximum working PV is the range of 5 MPam/s. the dimensional precision is very high, and produces extremely low noise.