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Bearing (Material Science)
Bearing (Material Science)
Bearing (Material Science)
Bearing (Material Science)
Bearing (Material Science)
Bearing (Material Science)
Bearing (Material Science)
Bearing (Material Science)
Bearing (Material Science)
Bearing (Material Science)
Bearing (Material Science)
Bearing (Material Science)
Bearing (Material Science)
Bearing (Material Science)
Bearing (Material Science)
Bearing (Material Science)
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Bearing (Material Science)

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  • 1. Bearing Materials
  • 2.  Bearings support moving parts, such as shafts and spindles, of a machine or mechanism.  Bearings may be classed as  (i) Rolling contact (i.e., Ball and roller) bearings.  (ii) Plain bearings.  Rolling contact bearings are almost invariably made of steel that can be hardened after machining.  Both plain carbon and alloy (Ni, Cr, Mo) steels are employed for different applications.
  • 3. PROPERTIES OF BEARING MATERIALS  A bearing material should:  Possess low coefficient of friction.  Provide hard, wear resistant surface with a tough core.  Have high compressive strength.  Have high fatigue strength.  Be able to bear shocks and vibrations.  Possess high thermal conductivity to dissipate heat generated due to friction between the bearing and the rotating shaft.
  • 4.  Possess adequate plasticity under bearing load.  Possess adequate strength at high temperatures.  Be such that it can be easily fabricated.  Possess resistance to corrosion.  Be such that it does not cause excessive wear of the shaft rotating in it, i.e., bearing material should be softer than the shaft material.  Possess antiseizure characteristics.  Be having small pieces of a comparatively hard metal embeded in a soft metal.  Maintain a continuous film of oil between shaft and bearing in  order to avoid metal to metal contact.
  • 5.  Possess ability to embed in itself any dirt, etc., present in lubricating oil.  Should be cheap and easily available.
  • 6. TYPES OF BEARING MATERIALS  Lead or tin based alloys (Babbitt metals)  Cadmium-based alloys.  Silver-based alloys.  Sintered bearing materials.  They may be divided as The high tin alloys with more than 80% tin and little or no lead. The high lead alloys with about 80% lead and 1—12% tin. The alloys with intermediate percentages of tin and lead.
  • 7. Typical compositions of A lead based alloy A tin based alloy  Pb 75% Sn 88%  Sb 15% Sb 8%  Sn 10% Cu 4%  — Lead base alloys are softer and brittle than the tin base alloys.  — Lead base alloys are cheaper than tin base alloys.  — Tin base alloys have a low coefficient of friction as compared to lead base alloys.
  • 8.  Lead base alloys are suitable for light and medium loads, whereas tin base alloys are preferred for higher loads and speeds.  Whereas tin base alloys find applications in high speed engines, steam turbines, lead base alloys are used in rail road freight cars.  Solidus temperature of Tin base alloys — Approx. 222°C  Solidus temperature of Lead base alloys — Approx. 240°C
  • 9.  Besides, both these alloys possess  Good ability to embed dirt  Good conformability to journal  Good corrosion resistance  Very good seizure resistance, etc.
  • 10.  Cadmium-based alloys possess (a) low coefficient of friction, (b) high fatigue strength, (c) high load carrying capacity, (d) low wear, good seizure resistance, (e) fair ability to embed dirt, and (f) poor corrosion resistance (using ordinary lubricants). Cadmium-based alloys were tried in automobile and aircraft industries and good results were obtained.
  • 11.  White metals are tin base or lead base bearing alloys and are usually referred to as babbitts.  They are:  Lead or tin-based alloys.  Aluminum based alloys.  Copper-based alloys.  Non-metallic bearing materials.  Cadmium-based alloys
  • 12.  Aluminum-based alloys  These alloys possess  (a) excellent corrosion resistance;  (b) fair conformability to journal;  (c) good ability to embed dirt;  (d) good seizure resistance;  (e) good thermal conductivitY but  (J) high coefficient of expansion.  — These alloys find applications as bearings in diesel engines and tractors.
  • 13. Silver-based alloys  Silver bearings are produced by the electro- deposition of a 0.3— 0.5 mm layer of silver on a steel support shell, with an inter mediate layer of Cu or Ni.  A 0.02-0.03 mm film of lead and indium is then deposited on top of the silver, and the indium diffused into the lead by heart- treatment at 180°C.  This covering layer aids in improving the running-in properties and the corrosion- resistance of the silver layer.  These are highest priced bearing alloys.  They are employed where other materials do not produce satisfactory results.  These alloys are used on the connecting rod
  • 14.  Copper-based alloys  The term bronze covers a large number of copper alloys with varying percentages of Sn, Zn and Pb.  Bronze is one of the oldest known bearing materials.  Bronze,  (a) is easily worked;  (b) has good corrosion resistance; and  (c) is reasonably hard.
  • 15.  Tin bronze (10 to 14% tin, remainder copper) is used in the machine and engine industry for bearing bushes made from thin- walled drawn tubes.  Copper-based alloys are employed for making bearings required to resist heavier pressures such as in railways.
  • 16. Thank You

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