Influence of consolidation process and sintering temperature on microstructure and mechanical properties of near nano- and nano-structured WC-Co cemented carbides

• Two powder metallurgy processes; sintering in hydrogen and sinter-HIP were used.
• Consolidation process, sintering temperature and GGIs influenced the properties.
• Cr3C2 reduced a carbide grain growth, increased hardness and fracture toughness.
• Relationship between Vickers hardness and fracture toughness is not linear.
• Larger amounts of GGIs are required in case of sintering in hydrogen atmosphere.

In this paper the influence of the consolidation process and sintering temperature on the properties of near nano- and nano-structured 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.