Shrinkage and microstructure evolution during sintering of cemented carbides with alternative binders

Cemented carbides are used in the cutting tools industry thanks to their exceptional mechanical properties. Manufactured by the powder metallurgy route, they are made of a hard WC phase with a ductile metallic binder, most commonly Co. Due to the lower availability of Co and its classification as carcenogenic material by the REACH European Regulation, new metallic binders have to be considered: Fe and Ni binders are investigated in this work. Because Co is the most common binder used in the hard metal industry for decades, there is still a lack of knowledge regarding the specific effect of alternative binders on shrinkage and microstructure evolution of cemented carbides. The purpose of this work is to understand the effect of binder nature specifically, comparing classic Co binder used in the industry to pure Fe and Ni binder including the influence of carbon content. Shrinkage behaviour and microstructure evolution of WC-M alloys (M = Co, Ni, Fe) are studied from dilatometry experiments as well as qualitative and quantitative microstructural characterisations. Solid state sintering is delayed to higher temperature for WC-Fe in comparison to WC-Co and WC-Ni alloys. Densification mechanisms are discussed in relation with dilatometry results, microstructural analyses, DFT calculations and a theoretical kinetic model from the literature.

Automated summary

This study investigates the effects of binders on shrinkage and microstructure evolution of cemented carbides, comparing Co used in the industry to Fe and Ni binders. It is found that WC-Fe requires a higher temperature for solid state sintering compared to WC-Co and WC-Ni alloys. Discussions in this study involve densification mechanisms in relation to dilatometry results, microstructural analyses, DFT calculations, and a theoretical kinetic model from literature.