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Influence of Consolidation Process and Sintering Temperature on Microstructure and Mechanical properties of Near Nano- and Nanostructured WC-Co Cemented Carbides

In this paper the influence of the consolidation process and sintering temperature on the properties of near nano- and nanostructured cemented carbides was researched. Samples were consolidated from a WC 9-Co mixture by two different powder metallurgy processes ; conventional sintering in hydrogen and the sinter-HIP process. Two WC powders with different grain growth inhibitors were selected for the research. Both WC powders used were near nanoscaled and had a grain size of 150 nm and a specific surface area of 2.5 m2/g. Special emphasis was placed on microstructure and mechanical properties ; hardness and fracture toughness of sintered samples. Consolidated samples are characterised by different microstructural and mechanical properties with respect to the sintering temperature, the consolidation process used and grain growth inhibitors in starting powders. Increasing sintering temperature leads to microstructure irregularities and inferior hardness, especially for samples sintered in hydrogen. The addition of Cr3C2 in the starting powder reduced a carbide grain growth during sintering, improved microstructural characteristics, increased Vickers hardness and fracture toughness. The relationship between hardness and fracture toughness is not linear. Palmqvist toughness does not change with regard to sintering temperature or the change of Vickers hardness.

nanostructured WC-Co cemented carbides; sinter-HIP; sintering in hydrogen; grain growth inhibitors; Vickers hardness; Palmqvist toughness

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