Effects of Carbon Content on the Properties of Sintered WC–NbC–10%Co Alloys

Abstract

Some properties of WC–NbC–10%Co cemented carbides have been studied in relation to carbon and niobium carbide contents. The measured values of their properties were examined in comparison with the results so far obtained by the present authors for various cemented carbides. The experimental results are as follows.(1) Niobium carbide is insoluble in the binder phase, as in the case of tantalum or titanium carbide in WC–TaC–Co, WC–TiC–Co or WC–Ti(Ta)C–Co alloys. (2) The amount of tungsten carbide dissolved in niobium cardide is about 18%. (3) The composition of the binder phase and the carbon content of the niobium carbide (NbC–WC double carbide) phase vary regularly in the three-phase region due to the slight change in carbon content. This resulted in regular changes in other various properties, as has been confirmed in the above various alloys. (4) The three-phase region extends with increasing niobium carbide content owing to the changes in the carbon content of the niobium carbide phase. (5) The phase diagram of the WC–NbC–10%Co alloy system has been established. (6) The WC–NbC–Co material appears to occupy a position intermediate between WC–TaC–Co and WC–TiC–Co materials.