There has been a requirement for automotive bearings materials to be free of the toxic material lead, in accordance with ELV regulations and from the perspective of environmental problems.
Currently, bismuth is used as a replacement for lead in copper alloy based main journal bearings and connecting rod bearings for automotive engines. In recent years, there has been changing to lead-free materials for truck engine bearings.
Compared with automotive engines, lots of contaminations in the oil and local contact between the shaft and bearings can occur in truck engines. The ability to tolerate contamination and local contact is therefore required for truck engine bearings.
In this development, we find that the addition of 8 mass% bismuth and 1.5 mass% molybdenum carbide particles into copper-tin alloy is effective for improving the ability which allow the contamination and local contacts.
The development of above mentioned lead-free copper alloy bearing material is described here.