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As the recent automotive engines are designed for higher performance, the rotating speed of the engines have been increased drastically. Therefore the engine bearings should be further improved to have better anti-seizure and wear properties under the high temperature at the high rotating speed. The authors have analyzed the necessary functions of the three layers copper-lead bearings at such operating conditions, and then improved and developed the overlay and the copper based bearing alloy with steel back. Physical and chemical properties for this new bearing were studied. Then the bearing performance tests were carried out including the high speed seizure tests and engine tests. From these test results, it was confirmed that this new bearing could be applied for the recent very high speed automotive engines.

The diffusion phenomena of tin and indium which are contained in the lead-base overlay of 3-layer copper-lead alloy bearings were studied. Easier diffusion of tin compared with indium decreases the corrosion resistance of the overlay, and the tin reacts with the underlayer to form brittle Ni-Sn or Cu-Sn intermetallic compound, resulting in weak bonding strength. Addition of copper into Pb-In overlay markedly restrains the diffusion of indium and therefore stabilizes the characteristics of corrosion resistance, bonding strength and mechanical properties for a long period. Cavitation tests, seizure tests and bearing fatigue tests were conducted on Pb-In-Cu overlay to study the feasibility of its application to actual engine bearings.