Tungsten Carbide-Cobalt Nanocomposites: Production and Mechanical Properties


Zhigang Zak Fang Department of Metallurgical Engineering, University of Utah

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Over the past decade, substantial research efforts have been directed toward the synthesis of nanostructured powders and thin films, which raise the prospects of advanced materials with dramatically improved properties based on nanoscale grain structure. It would be particularly advantageous to exploit these improved properties to extend the lifetime and robustness of tungsten carbide tools. As a result of this industrial significance, intensive efforts are being made to produce these tungsten carbide-based materials with finer and nanoscale grain size.

Many differing process technologies have been introduced to produce both nanostructured tungsten carbide and tungsten carbide–cobalt composite powders. Process technologies range from improvements to the conventional solid-state synthesis to more radical techniques such as spray conversion and vapor deposition methods.

For many applications, nanocrystalline powders have to be consolidated and sintered to make bulk materials and engineering components. However, most nanostructured powders lose their nanoscale characteristics after sintering because of extremely rapid rate of grain growth during sintering. Controlling grain growth during sintering and producing bulk nanocrystalline hard materials remain a critical technology challenge.

For those materials, especially metallic structural materials, the inability to achieve nanoscale grain sizes at sintered state also hinders efforts to characterize and understand their mechanical behavior as nanostructured materials. Cemented tungsten carbide is one of those materials. There are strong indications of dramatic shift in the mechanical behavior when the grain sizes of tungsten carbide cobalt (WC–Co) become progressively finer. But the potential of fully consolidated cemented tungsten carbide with true nanoscale grain sizes (< 30 nm) remains unexplored.