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Emission control and other restrictions prescribed in the EU's recent EUROIV regulations require automobile manufacturers to decrease NOX and PM (Particulate Matter) in exhaust emissions. Diesel engines in recent years tend to have higher cylinder pressure in pursuit of higher performance and meeting emission regulations. At the same time, under the ELV (End-of-Life Vehicles) regulation, use of lead, which is an environmental pollutant, in automobile parts has become increasingly difficult in recent years. Accordingly, we have developed lead-free overlay for tri-metal copper bearings for applications of highly specific load. We chose a dual-layer structure, bismuth and silver overlay. This type of structure can create fatigue resistance without compromising the two advantages of lead overlay: conformability and anti-seizure property.

As the recent engines are designed for higher performance, piston pin bushing used for small end of connecting rod must endure higher dynamic load and oil temperature conditions. Therefore, the bushing is required higher wear resistance and anti-corrosion. And it is also expected to develop the bushing without lead due to environmental concerns. In this report, lead free copper based bushing alloy was studied. At first, in order to keep the anti-seizure property without lead, we studied the effects of hard particles added into copper based alloy. Second, we evaluated the effect of addition of hard particles on wear resistance and anti-corrosion.

Recently, there has been a tendency of high power and high speed in automotive engines. In addition they have been also required high reliability. And engine bearings have been required to be advanced in wear resistance as well as seizure resistance. Therefore, copper-lead alloy bearings with overlay, which have better seizure resistance, have been widely used for high speed engines up to the present. But it becomes very important for them to advance the overlay wear resistance. In this paper, the composite overlay is mainly researched to improve wear resistance regarding kind of hard particles and their amounts in the overlay.