Development of Lead Free Copper Based Alloy for Bushing Under Boundary Lubrication

A copper based bushing alloy is used under boundary lubrication for the sliding part of a fuel injection pump etc. for automotive diesel engines.

Lead is added to a copper based alloy bushing, because seizure resistant property is an important factor under boundary lubrication. However reducing the use of lead, an environmental pollutant, is required from environmental concerns.

Therefore, a lead free bushing alloy was studied in this paper. Concept of material design is to prevent adhesion between a bushing alloy and a mating shaft leading to less wear under the boundary lubrication. The tested material is basically copper-based alloy to which low melting metal instead of lead, hard particles and solid lubricant are added. Tribological and mechanical properties of the material were evaluated in terms of seizure resistance, fatigue strength, conformability and cavitation resistance. The surface of the busing after the test was analyzed by electron probe microanalyzer (EPMA) to examine wear mechanism. Finally the bench test of a fuel injection pump was carried out and the applicability of the developed material is well verified.