Sintering shrinkage of WC-Co and WC-(Ti,W)C-Co materials with different carbon contents

The sintering of cemented carbides based on WC-Co with different carbon contents and additions of (Ti,W)C has been studied by dilatometry and analysed in terms of a densification model. Shrinkage starts around 1000degreesC for WC-Co and in the range 1100-1250degreesC for WC-(Ti,W)C-Co. Although a high carbon content initially delays shrinkage in WC-Co it leads eventually to high shrinkage rates and a fully dense material in the shortest time. Practically no difference was found between low and medium carbon contents. For WC-(Ti,W)C-Co, onset of shrinkage depends more strongly on composition and increases with decreasing carbon content. Shrinkage rates are described with a proposed model based on uniaxial viscosity, viscous equivalent of Poisson's ratio and sintering stress. The three densification stages observed for WC-Co materials reduce to two stages for WC-(Ti,C)C-Co, where higher apparent activation energies also are observed during solid state sintering. (C) 2004 Elsevier Ltd. All rights reserved.