English

Abstract

Powder Metallurgy (PM) deals with products and processes which use raw material in the form of powders that are compacted into the required shape and size using suitable moulds. These compacted powders are called „Green Compacts‟. The properties of the component produced by PM processes are influenced by powder characteristics such as composition, morphology, particle size, distribution, and method of compaction. The first step in PM process is preparation of „green‟ compacts. Uni-axial pressing is one of the most widely used compaction method for the preparation of green compacts. The process is characterized by three distinct phases namely re-arrangement of powder particles, inter-particle sliding and plastic deformation of powder particles. In this paper the effect of metal powder composition, particle morphology on „green‟ density under uni-axial pressing is presented. Iron powders with average particle size in the range of 2 to 150 microns show a linear relationship between green density and pressure. Green densities greater than 75% can be achieved with a pressure of 500 MPa. Micron size aluminum, nickel, titanium cobalt and iron powders were compacted under 200 MPa pressure to evaluate the effect of composition. Aluminum had the highest green density of 90%, followed by nickel at 75%, titanium at 65% and iron, cobalt at 55%. The three distinct phases of powder densification, mentioned earlier, were clearly observed in the porosity versus pressure plots for all the powders