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Recently, a lead-free Al-Sn-Si alloy bearing with metallic overlay has started to be used for a portion of automotive engines. This bearing has good anti-seizure and excellent running-in properties, and is an environmentally friendly alternative to the current copper-lead alloy with lead based overlay in accordance with the ELV regulation for the removal of lead from bearings. But automotive engines have been required to exhibit higher performance in order to enhance their commercial power, which tends to require the engine bearing to perform under higher temperature due to higher specific load on the bearing and higher rotational speed of the crankshaft. It is clear that the current lead-free aluminum alloy bearing is not satisfactory with respect to fatigue strength in some cases, and requires higher strength under the higher temperature conditions.

Recently, a Lead-free aluminum alloy bearing with available fatigue strength is partially applied for plain bearings in automotive engines as replacement of a conventional copper alloy bearing with lead based overlay, according to requirement of ELV regulation, which requires the lead removal from bearing. However, our recent investigation made clear that the aluminum alloy bearing did not have enough running-in property when operated under severe condition of thinner oil film in recent automotive engine with further higher performance. Based upon these backgrounds, a lead-free bearing was newly developed by applying overlay onto the aluminum alloy bearing for better running-in property of the bearing.