Influence of sintering parameters on the microstructure and mechanical properties of WC-Co hardmetals

Abstract

The influence of sintering temperature, dwelling time at maximum temperature and carbon content on the microstructure and on the mechanical and magnetic properties of WC-6%Co hardmetal was investigated. Samples were sintered according to a central composite design and subsequently analysed with respect to microstructural parameters (average WC grain size, binder mean free path and contiguity), as well as mechanical (hardness, transverse rupture strength and toughness) and magnetic (magnetic saturation and coercivity) properties. Microstructural parameters were determined using a Matlab®-based program developed for the evaluation of EBSD images. Results show that in order to maximize both hardness and TRS sintering should be performed in the low temperature range, i.e. < 1400 °C, while dwelling time should not be too short, at least 75 min. This is particularly important for low carbon parts, since longer dwelling times are required to provide the microstructure with the necessary homogeneity required for high TRS.