Journal of Powder Materials

Research Article

[English]
Effect of Bimodal WC Particle Size Distribution on the Mechanical Properties of WC–Mo₂C–Co Cemented Carbides: Jinwoo Seok, Jong Tae Kim, Juree Jung, Bin Lee, Junhee Han, Leeseung Kang; J Powder Mater. 2026;33(1):13-21. Published online February 28, 2026; DOI: https://doi.org/10.4150/jpm.2025.00500

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Abstract PDF: In this study, the influence of bimodal WC particle size design on the microstructure and mechanical properties of WC–27 wt.% Mo₂C–10 wt.% Co cemented carbides was systematically investigated. Bimodal hard-phase designs were realized by combining ultrafine WC (300 nm) and coarse WC (1.8 μm) at various ratios, followed by consolidation via spark plasma sintering (SPS). During sintering, Mo₂C preferentially dissolved into the Co-rich liquid phase due to its higher solubility than WC, forming a Co–Mo–C liquid. During sintering progresses, ultrafine WC selectively dissolved owing to its high interfacial energy, gradually transforming the liquid composition into a Co–Mo–W–C system. Owing to the short holding time and rapid cooling rate of SPS, the η-phase (M₆C) formed during sintering remained metastable. Meanwhile, selective dissolution–reprecipitation resulted in the formation of Mo₂C-based core–rim structures with W enrichment in the rim region as (Mo, W)₂C. As the fraction of ultrafine WC increased, the hardness increased from 1769 to 1997 kgf/mm2, whereas the fracture toughness exhibited an insignificant difference from 6.56 to 6.65 MPa•m¹ᐟ². Fracture behavior analysis revealed that crack deflection and crack bridging occurred at the Mo₂C core–rim interfaces, effectively suppressing straight crack propagation. These results demonstrate that the introduction of ultrafine WC plays a dominant role in enhancing mechanical performance, and that bimodal WC design combined with Mo₂C addition is a highly effective strategy for developing high-performance cemented carbides for machining

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