Advantages and Limitations of Lead-Free Bearing Materials

Due to strict lead recycling regulations put upon discarded automobile engines, removing lead from new automotive engines became essential. Removing lead found in batteries from discarded automobiles is fairly straight-forward and inexpensive; however, much labor and cost is associated with removing lead containing engine bearings. Due to the relatively light loading applied to automotive gas engine bearings, lead-free aluminum alloys have been developed. Many experts predict that this lead-free trend will carry over to non-automotive bearings as well. Many of these non-automotive engines are run on diesel fuel and have much higher loading on the bearings. The current generation of lead-free aluminum alloys just cannot carry the loads required by these engines. Therefore, there has been efforts on developing lead-free copper based bearing alloys. This paper reviews one process that was undertaken to develop lead-free copper based alloy to be used in these highly loaded, non-automotive lead-free engine bearing types. This process included a fundamental understanding of the tribological role of lead in copper based bearing alloys, as well as a thorough performance screening of lead-free bearings types based on this lead-free lining and a comprehensive review of the test results. Also included in this paper are some future development plans in the world of lead-free copper based bearings alloys.© 2006 ASME