Some characteristics of the binder phase in cemented carbides

This paper examines the properties of binder alloys and mixtures that relate to possible composition of the binder phase in cemented carbide alloys with some emphasis on the sub-stoichiometric state in metal carbides. The investigation looks for a better understanding of the role of carbon deficiency in the performance of alloys in industrial applications. Cobalt was the primary metal chosen for the study with a small companion study of nickel. Low concentrations of carbon; tungsten; a simple mixture of tungsten and carbon; tungsten carbides of both high and low carbon content; di-tungsten carbide; and a solid solution of 50/50 tungsten-titanium carbide were pressed, sintered and heat treated. Sintered materials were tested for mechanical properties in tension and for magnetic properties in strained and unstrained conditions. With the exception of carbon all the alloy additions exhibited some degree of solution strengthening. Tungsten-titanium carbide was found to be the most effective additive followed closely by di-tungsten carbide and metallic tungsten. Some relationship was found between mechanical and magnetic properties. Results support a model where WC acts as the primary solution strengthening agent. Tungsten in solution caused by the presence of sub-stoichiometric tungsten carbide further increases the solution strengthening. (C) 1997 Elsevier Science Limited.