Spark plasma sintering behavior of nanocrystalline WC-10Co cemented carbide powders

Abstract

Microstructure and mechanical properties of WC-10Co cemented carbides fabricated by spark plasma sintering (SPS) process were investigated. Nanocrystalline precursor powders were prepared by spray drying process from solution containing ammonia meta-tungstate and cobalt nitrate, and followed by reduction and carbonization into nanocrystalline WC/Co composite powders by a mechano-chemical process. The WC particles of about 100 nm in diameter were mixed homogeneously with Co binder. The nanocrystalline WC-10Co powders were consolidated by SPS process at temperature ranged 900-1100 degreesC and under a pressure of 50 or 100 MPa, respectively. Optimum consolidation conditions, such as temperature and pressure, were determined by analysing the dimensional changes of powder compact during SPS process. Hardness and fracture toughness of consolidated WC-10Co cemented carbide were measured by using a Vicker's indentation test. The solute content within the Co binder phase of WC-10Co cemented carbide was evaluated by measuring the saturated magnetic moment. It is found that the hardness of cemented carbide was dependent on the density and grain size of WC. The fracture toughness of cemented carbides increased with increasing the saturated magnetic moment, while decreased rapidly when the liquid Co phase was formed during sintering. (C) 2002 Elsevier Science B.V. All rights reserved.