Influence of starting powder on the microstructure of WC-Co hardmetals obtained by spark plasma sintering

WC-Co hardmetals using different starting powders were densified by spark plasma sintering (SPS). Sintering cycles were performed at 1240 degrees C for the WC-12 wt.% Co-0.45 wt.% VC grade and 1280 degrees C for the WC-6 wt.% Co grade, applying a pressure of 60 MPa in combination with a heating rate of 100 degrees C/min. The influence of the carbon content and homogeneity of the starting powders on the final microstructure and mechanical properties was investigated. A thin graded surface layer is observed in case of slightly carbon deficient starting powder. Co agglomerates were observed in the SPS materials obtained from lower energetically multi-directionally mixed WC-Co powder, whereas a homogeneous microstructure was obtained when using attritor-milled or chemically synthesized WC-Co starting powder with adjusted carbon balance. The observed microstructures are related to the measured mechanical properties. (C) 2007 Elsevier B.V. All rights reserved.status: publishe