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The recent demands for higher performance and lower fuel consumption of automotive engines require the bearings to operate under severe conditions. One of the problems with conventional aluminum alloy bearings used under these conditions is the low wear resistance. A new aluminum alloy bearing that allows a higher wear resistance is developed by controlling Si particle size and lining hardness. The mechanism to upgrade the wear resistance are the concentration of enlarged Si particles on the sliding surface and to prevent falling off Si that are held by sufficient lining hardness. Wear resistance of this bearing is 4-5 times better compared with the conventional bearings and seizure resistance is two times better than the conventional bearings.

Aluminum alloy bearing with overlay, which was developed for automotive engine bearing material, has both advantages of conventional aluminum bearing and copper-lead bearing with overlay. This new bearing consists of four(4) layers of tin overlay, nickel intermediate layer, aluminum alloy lining and back steel. This paper reports that seizure, fatigue and wear resistance are improved in order to prevent nickel exposure which may easily seize on the entire sliding surface from the interface structure between the overlay and aluminum alloy and maintain low tin-nickel compound creation which is prepared by the intermediate layer due to heat from the overlay plating bath; which is also examined.

High tin and aluminum alloy bearings can seize easily when used with nodular cast iron shafts. The authors have investigated the process of seizure between such nodular cast iron shafts and high tin and aluminum alloy bearings, and found that the seizures are normally caused by a combination of burrs around the graphite at the surface of the nodular cast iron shafts and abrasive aluminum debris adhering to the shaft. In an attempt to remove the burrs and abrasive aluminum debris, the authors dispersed hard particles in the alloy bearings. The new alloy used has a chemical composition of Al Si 3, Sn 10 and Pb 1.5 and, as a result bearings formed from it do not require a lead-based overlay. This arrangement provides much higher seizure resistance than overlayed copper and lead alloy bearings when used with nodular cast iron shafts. The bearings made with this alloy can be used in all engines with nodular cast iron shafts without any problems whatsoever.