Influence and effectivity of VC and Cr3C2 grain growth inhibitors on sintering of binderless tungsten carbide

For the production of hard, high temperature and abrasion resistant parts, like water-jet nozzles or pressing tools for forming glass lenses, binderless cemented carbide is used. In this work, the consolidation of tungsten carbide with additions of VC and Cr3C2 grain growth inhibitors is studied. Tungsten carbide powder dry or wet milled was consolidated by dry pressing, debindering and gas pressurized sintering and, alternatively, by spark plasma sintering. The effect of adding VC and Cr3C2 to binderless tungsten carbide on the grain growth was studied with contents being 0; 0.1; 0.3; 0.5; 0.7 and 1.0 wt.%. Samples with an ultrafine microstructure free of abnormal grain growth, a hardness of 25.5 GPa and a fracture toughness of 7.2 MPa·m1/2 were archived by conventional sintering. Both carbides reduce grain growth, but with Cr3C2 a finer microstructure can be achieved at lower amounts. Compared to the same amount of Cr3C2, the addition of VC results in smaller grains but lower hardness and fracture toughness.

► Dense binderless tungsten carbide with ultrafine microstructure was produced by conventional pressurized sintering. ► It was shown that grain growth inhibitors act similar as in hard metals with cobalt binder. ► i.e., chromium carbide that is thought to reduce grain growth by influencing processes in the binder phase is also efficient in solid state sintering systems. ► Unlike to WC-Co the grain growth inhibitor chromium carbide seem to retard grain growth at lower amounts and produces harder binderless tungsten carbide than with the grain growth inhibitor vanadium carbide.