DEVELOPMENT OF , Al-Zn-GRAPHITE COMPOSITE BY POWDER TECHNIQUE FOR ANTIFRICTION APPLICATIONS

Abstract

Aluminium based bearing are known for their heavy load capacity under relatively low velocity applications. Number of compositions are currently available namely Al-Sn, A1-Zn-Sn, Al-Graphite etc. Addition of graphite has been found to improve wear resistance and antiseizure characteristic of Al-based bearings. However, its • usefulness can be fully exploited when optimum quantity of graphite is confirmly - distributed in the matrix of aluminum. The present investigation is meant to optimize graphite content in such materials with and object of getting improved wear resistance under dry condition of running. In order to get the best distribution, blending/ mechanical alloying followed by high temperature direct powder -forging has been attempted. Number of compositions were developed based on Al-Zn-Graphite and Al-Graphite. However, Zn did not yield satisfactory product. Al-Graphite composite, on elaborate characterization yielded satisfactory results.. Microstructural investigation revealed that there is. a considerable porosity in blended products and this increases with increasing percentage of graphite. However mechanically alloyed products yielded uniform microstructured free of porosity and very fine distribution of graphite in aluminium matrix. Wear testing revealed that wear loss decreases with increasing percentage of graphite (in 6 -10% range) content in case of mechanically alloyed products whereas the trend is just opposite