Song Zeng,Jiuming Yu,Wenfu Chen,Chang Jiang,Youxing He,Yiyou Wu,Lei Lu,Linwei Zhang
This study elucidates the chemical mechanism for synthesizing Y-doped tungsten-based precursors using a wet chemical method and investigates its impact on WC-Co cemented carbides. It is found that the acidity (H + concentration) critically determines the precursor phase, morphology, and Y doping efficiency. At moderate acidity, amorphous white tungstic acid nanoparticles rich in W–OH bonds are formed, enabling efficient Y doping (0.34 wt%) through coordination. The resulting Y-doped WC-Co sintered body exhibits a refined microstructure: the average WC grain size decreases from 0.468 μm to 0.388 μm, the WC phase increases from 89.47% to 92.45%, and the brittle Co₃W₃C phase decreases from 9.46% to 6.64%. Y₂₈O₇₂Co₀.₁₅-type precipitates, identified at grain boundaries, contribute to grain refinement via Zener pinning and likely help stabilize the phase composition. This work clarifies the complete pathway from precursor design to microstructure optimization in WC-Co alloys.
In this work, polycrystalline cubic boron nitride (PcBN) carbide insert was prepared by a six-anvil high-pressure apparatus at 1500 °C and 5.5 GPa, integrated sintering with different alloy substrates of the Co content. This work studied the effects of different Co content in alloy substrates on phase composition, microstructure, and mechanical properties of the PcBN carbide insert. The result shows that the binder reacted with cBN particles to produce AlN, AlCo, TiB 2 , W 2 B, and Co 2 B. At the same time, transgranular fracture is wide spread in the sintered body. The flexural strength and hardness of the PcBN carbide insert first increase and then fall. When the alloy substrate is WC-11.5 wt% Co, the PcBN carbide insert shows excellent comprehensive performance, with the flexural strength and hardness reaching 1675.67 MPa and 4100.51 Hv, respectively. Through integrated sintering, Co in the alloy substrate diffused and reacted with the binder in the cBN network at the bonding interface, forming a transition area that significantly improves the bonding strength.
HighlightsWhat are the main findings?Y doping reduces WC/Co interfacial energy and enhances bonding strength. Y-W orbital hybridization forms strong covalent bonds at the atomic interface.Material achieves dual improvement: Hardness (1454 HV) and toughness (9.84 MPa·m1/2).Optimal 0.5 wt.% Y refines grains and uniformly distributes the Co binder phase. Wear resistance is significantly improved, with the lowest wear rate at 0.5 wt.% Y.What are the implications of the main findings?Provides an atomic-scale mechanism for rare earth-enhanced cemented carbides and offers a design strategy for co-optimizing hardness and toughness in composites;Validates the integration of first-principles calculations with experimental validation;Identifies an optimal Y doping threshold for superior comprehensive properties.This study aims to clarify the optimization mechanism of yttrium (Y) doping on the interfacial bonding and macroscopic properties of WC/Co cemented carbides, with the goal of achieving materials that combine high hardness, high toughness, and excellent wear resistance through interfacial regulation. Combining first-principles calculations and experimental verification, the interfacial energy, density of states, and charge density of WC/Co and WC/CoY interfaces were systematically investigated. Three alloys (WC-10Co, WC-10Co-0.5Y, and WC-10Co-1Y) were prepared, and the effects of Y addition were quantitatively evaluated through microstructural characterization, mechanical testing, and tribological experiments. The calculation results indicate that Y doping reduces interfacial energy, enhances interfacial bonding, and increases surface energy, which contributes to improved toughness. At the atomic scale, the orbital hybridization between Y and W promotes the formation of strong covalent bonds at the interface, thereby enhancing interfacial bonding strength. The experimental results show that the introduction of Y significantly improves the overall performance of the material, with the alloy containing 0.5 wt.% Y exhibiting the best performance. Its Vickers hardness reaches (1454 ± 1.3) HV, fracture toughness is (9.84 ± 0.15) MPa·m1/2, and the wear rate is as low as 0.794 × 10−5mm3·N−1·m−1.
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