Substitute alloys as bearing materials

Modern engineering depends in many instances upon bearings, components which allow relative movement to occur between the members of a mechanism. Bearings are usually designated plain or rolling. The trend in soft metal plain bearings is to increase the load carrying capacity with the minimum loss of friction and wear properties. Conventional alloying techniques of hardening additions have been fully exploited. Alloys of high strength at the operating temperature such as copper-lead have been developed but have corrosion problems. Such alloys find use as inter layers for lead-tin or lead overlays. Aluminium alloys offer a better combination of strength, wear resistance and freedom from lubricant corrosion. Successful techniques of bonding aluminium to steel shells have been developed thus rapidly increasing the potential of aluminium in automotive bearing applications. The metallurgy of plain bearings, the properties, uses and comparison of substitute materials are discussed. Engineering progress imposes severe requirements on rolling mechanisms and in some specific applications such as aero-engines, atomic reactors and space exploration, due to extreme operating temperatures and environments conventional En 31 steels are not suitable and superior materials such as high speed tool steels are required. This has led to the development of substitute of high speed tool steels molybdenum and vanadium. The simulation service testing of potentially suitable substitute materials and metallographic investigation is described. (Mr. D. Scott, Head of Metallurgy Section, High Temperature Materials Division, National Engineering Laboratory, Glasgow