When a sufficient amount of the bronze asperities become embedded on the surface, wear decreases and friction forces decrease. The basic copper - tin alloy, used for gears, has developed into a series of five popular gear bronzes. 427-93A. Variations are not large. This allows for good machinability and the lead particles will embed any abrasive media during the wearing in period. It increases corrosion resistance and promotes a smaller crystal size in the castings.
Smaller crystals result in less chemical segregation and higher mass physical properties.
The Nicomet series of copper alloys perform well in gear applications requiring higher mechanical strength and corrosion resistance. These gear bronzes can not be produced by wrought processing such as extrusion, drawing, rolling or forging. They must be used as cast. The high tin content will cause extrusion billets to fracture. Lower tin contents can be extruded and drawn into small diameters.