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Copper based bearing materials

Dr. Dmitri Kopeliovich

The design of internal combustion engines has a tendency of decreasing the engine dimensions. This tendency leads to more compact bearings and consequently to higher specific alternating loads applied to them.

Copper based Engine bearing materials provide superior fatigue strength (load capacity).

Copper based bearing alloys commonly contain tin (up to 10%) as a strengthening component and a soft component (lead or bismuth) distributed in a copper-tin matrix as a separate phase in form of small particles.
Soft component imparts to the material anti-friction properties (compatibility, conformability, embedability).
Maximum content of soft phase is about 25%.
Copper based bearing alloys are manufactured by either casting or sintering technology.

Tri-metal cast bearing.png  Tri-metal sintered bearing.png

Despite the presence of soft components in most copper based bearing alloys their anti-friction properties are poor therefore copper (bronze) bearings are rarely used in engines in monometal (solid) or bi-metal (steel backed) forms.
Typical copper bearings are steel backed and overplated with a thin sliding layer (overlay) of a soft material (tri-metal structure). The overlay improves the anti-friction properties of the copper alloy.
Modern copper based bearing alloys do not contain lead because of its harmful effect on the environment. Lead in lead free alloys may be substituted by harmless bismuth having excellent anti-friction properties comparable with lead.

Load carrying capacity of copper based bearings is determined by the fatigue strength of the overlays:

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Characteristics of some copper based engine bearing materials

Composition Technology Structure Hardness, HV Diffusion barrier Overlay Applications
CuPb25Sn1 Cast Tri-metal 55 Nickel Pb10Sn2Cu Low loaded bearings
CuPb23Sn1.5 Cast Tri-metal 60 Nickel Al20Sn sputter Highly loaded conrod bearings
CuPb23Sn1.5 Cast Tri-metal 60 no or Nickel Pb10Sn12In Medium and highly loaded bearings
Cu24Pb243.5Sn Cast Multilayer 65 Nickel Pb10S3Cu + MoS2 in resin Racing car engine bearings
Cu20Pb3Sn Cast Tri-metal 65 Nickel Pb10Sn3Cu Medium loaded bearings
Cu15Pb7Sn Cast Bi-metal 80 no no Small end bushes
Cu15Pb7Sn Cast Solid 80 no no Thrust washers
Cu10Pb10Sn Cast Bi-metal 100 no no Highly loaded Small end bushes
Cu10Pb10Sn Cast Solid 100 no no Highly loaded Small end bushes
Cu8Al Cast Solid 145 no no Highly loaded bushes, lead free
Cu24Pb1Sn Sintered Tri-metal 55 Nickel Pb10Sn2Cu Low loaded bearings
Cu5Sn1Ag Sintered Tri-metal 80 no MoS2 in resin Medium loaded bearings, lead free
Cu22Pb1Sn Sintered Multilayer 55 Nickel NiSn + SnCu Medium and highly loaded bearings
Cu24Pb3.5Sn Sintered Tri-metal 65 Nickel Pb10Sn3Cu Medium loaded bearings
Cu20Pb4.5Sn Sintered Tri-metal 70 Nickel Pb10Sn5Cu Medium and highly loaded bearings
Cu10Pb10Sn Sintered Bi-metal 100 no no Highly loaded Small end bushes
Cu3Bi10Sn Sintered Bi-metal 130 no no Highly loaded bushes, lead free

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copper_based_bearing_materials.txt · Last modified: 2018/02/03 by dmitri_kopeliovich
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