- [Korean]
- Optimization of Mechanical Properties in WC–Mo₂C–Co Cemented Carbides via Dual Hard-Phase Based Heterogeneous Microstructure Design
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Jinwoo Seok, Jong Tae Kim, Juree Jung, SongYi Kim, Bin Lee, Junhee Han, Leeseung Kang
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J Powder Mater. 2025;32(5):428-436. Published online October 31, 2025
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DOI: https://doi.org/10.4150/jpm.2025.00297
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 Abstract
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- WC–Mo₂C–Co cemented carbides were fabricated to investigate the effects of Mo₂C addition on microstructure and mechanical properties. Dual hard-phase design using WC and Mo₂C was employed to optimize the balance between hardness and toughness. Spark plasma sintering (SPS) was conducted at various temperatures after ball milling, and 1300 °C for 5 min was identified as the optimized sintering condition, achieving complete densification and phase stability. The addition of Mo₂C refined the microstructure by suppressing abnormal WC grain growth through preferential dissolution of Mo₂C into the Co binder. Hardness increased up to 1769 Hv30 due to grain refinement and solid-solution strengthening, while promoted η-phase formation and reduced fracture toughness.The 27Mo₂C composition exhibited the most balanced combination of hardness and toughness. These results demonstrate that controlled Mo₂C addition enables dual hard-phase strengthening and microstructure optimization in WC–Mo₂C–Co carbides for advanced cutting and forming applications.
- [English]
- Effect of Bimodal WC Particle Size Distribution on the Mechanical Properties of WC–Mo2C–Co Cemented Carbides
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Jinwoo Seok, Jong Tae Kim, Juree Jung, Bin Lee, Junhee Han, Leeseung Kang
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Received December 16, 2025 Accepted February 27, 2026 Published online February 27, 2026
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DOI: https://doi.org/10.4150/jpm.2025.00500
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Abstract
- 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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