Seizure resistance characteristics of Cu–Pb bearing alloys

Copper–lead alloys with lead content from 11·5 to 50 wt-% were prepared by impeller mixing and bottom discharge chill casting. Microstructures of the as cast alloys were examined by optical microscopy. After evaluating room temperature mechanical properties of the alloys, their seizure resistance characteristics were assessed using a bearing testing machine (rig type) designed and fabricated for the purpose. Bearing tests were performed under different conditions of lubrication. The effects of load and a dimensionless bearing parameter known as the bearing characteristic number on the coefficient of friction of different alloys were investigated. In oil (SAE-10) lubrication tests, copper and leaded coppers (11·5–50 wt-%Pb) were able to run without seizure even in the high friction regions of mixed film and boundary friction zones. In both semidry and dry sliding conditions the coefficient of friction decreased and the seizure load increased with increased lead (42 wt-% ) content of leaded coppers. Also, a leaded copper bearing under semidry conditions showed greater seizure resistance (seizing load) than it did in dry sliding conditions. Copper–lead alloys have shown their ability to absorb and use a lubricating oil to reduce friction in the event of the oil supply failing.MST/1614