Carbon trapping at the solid–liquid interface in cemented carbides

Inter-diffusion between the hard ceramic and ductile metallic phases in composite materials such as cemented carbides governs their mechanical properties. Understanding atomic-scale diffusion at these interfaces is key to uncovering the mechanisms that dictate microstructure evolution, establishing a foundation for tailoring the properties of WC Co composites through precise interfacial control. The interface between tungsten carbide (WC) and liquid cobalt (Co) is investigated using molecular dynamics simulations. An integrated approach is presented for computing the solid–liquid interfacial free energy by combining computer vision aided interface detection with the Capillary fluctuation method. Significant inter-diffusion is observed, with atomic displacements primarily localized at the interface for W and C, while Co exhibits homogeneous behavior in the liquid phase. The formation of C C bonded structures at the interface is identified as a critical factor influencing diffusion, introducing localized structural rigidity that reduces atomic mobility. Additionally, premelting phenomena below bulk melting temperatures gives rise to a heterogeneous interfacial zone containing residual solid WC patches and molten W-Co alloy. The inter-diffusion coefficients for W, C, and Co compare well with prior computational and experimental studies, validating the methodology. These findings offer new insights into the atomic-scale mechanisms driving interface evolution and provide a foundation for tailoring the properties of WC Co composites through precise interfacial control.