Thermodynamic assessment of hardmetals with alternative binders and experimental validation

Abstract

Hardmetals are very well established due to their remarkable mechanical properties and wide range of applications. Cobalt is the favourite binder in WC-based cemented carbides, thus most sintering studies have been dedicated to the WC-Co system. However, the demand for carbide components with improved wear and corrosion resistance, is a reality in today's market. Sintering of hardmetals with alternative binders has revealed differentiated paths to reach the final microstructures but, in general, both a thermodynamic assessment and experimental studies to tailor and optimize the microstructural design are still missing.Alternative binders, constituted by Co and Ni alloys, and other alloying elements such as Cr and Mo, were used. This work aims to investigate the microstructural design of the new composites, using thermodynamic calculations based on CALPHAD methodology and Differential Thermal Analysis experiments. Wetting experiments were also conducted to measure the contact angle between the molten binder and the ceramic phase to further validate this approach. The microstructures of metal-ceramic interfaces and related composites were analysed by optical and scanning electron microscopy and the results were correlated with the reaction paths and overall hardmetal compositions.