Sintered Steels with Inert Hard Phase Produced by Mechanical Alloying in Ball Mill

Abstract

Iron based composites, with alumina or niobium carbide as a hard phase, have been developed in which the hard phase is dispersed finely in the iron matrix by means of mechanical alloying in either an attritor or a horizontal ball mill. These alloys consist of 10 vol.-% hard phase, carbon, either boron or phosphorus as a liquid phase activator, and (in one case) metallic molybdenum. Using liquid phase sintering between 1150 and 1250°C, depending on the alloy, relative composition densities of 94–99% have been achieved, providing wear behaviour and mechanical properties comparable to high speed steel. It is shown that the ball milling time required for highest sintered density is heavily dependent on the milling conditions. The suitability of different iron based powders and their effect on microstructure and mechanical properties have been investigated. PM/0688