Metastable austenite and mixed carbides in WC-Fe/Ni/Cr/Mo cemented carbide composites

This work investigates how austenite stability and phase composition varies across multiple carbon contents for a cemented carbide with a steel binder alloyed with nickel, chromium and molybdenum. The results are compared with predictions done by thermodynamic calculations and property models designed to predict the austenite stability for steel. It is found that it is possible to predict the martensite fraction in the metallic binder with reasonable accuracy. Phase identification by electron diffraction showed that mixed carbides of the form M 23 C 6 and M 7 C 3 can be found in the microstructure and that these are enriched in chromium and depleted in nickel. • Iron-based binders in cemented carbides can be designed to contain both austenite and martensite in varying fractions. • The empirical models developed to determine the martensite fraction for steels can with some modifications be used also for cemented carbides. • Chromium forms mixed carbides of the type M 23 C 6 or M 7 C 3 , where the latter appear at higher carbon contents. • Chromium will enrich in the mixed carbides while nickel will enrich in the remaining metallic binder.