Abstract WC-Co composite powders with different particle sizes and Co contents were prepared by ball milling WC and Co powder mixtures for different durations. Functionally graded WC-Co cemented carbides with both Co content and WC grain size gradient were prepared by lamination pressing different WC-xCo (x = 10, 15, 20) powder mixtures and microwave sintering the layered compacts. The WC-xCo powder mixtures were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), and the phase composition and microstructure of the functionally graded cemented carbides (FGCCs) were investigated by XRD, and FE-SEM coupled with energy dispersive spectroscopy (EDS). Mechanical behaviors of the layered WC-Co materials were measured and compared with those of WC-Co cemented carbides with single composition. The results showed that increasing the milling time from 6 to 24 h, results in the decrease of the particle size of WC-Co composite powders from 0.31 to 0.11 µm. After lamination pressing and microwave sintering, the WC-Co samples show nearly complete densification with a relative density higher than 99.7% and no ƞ-phase was detected in the FGCCs. The Co content and WC grain size in FGCCs decrease from the core to the surface. Homogenization of Co has hardly occurred and no cracks have formed between the layers in the sintered samples. In the inner layer, the mean WC grain size is 529 nm, while in the outer layer it is only 274 nm. Because of the difference in Co content and WC grain size, FGCCs have a Rockwell hardness of 90.75 HRA at the surface, which decreases to 86.75 HRA in the core. However the fracture toughness increases from 11.53 at the surface to 18.12 MPa m −1/2 in the core. The present results show that FGCCs with high outer layer hardness and high inner layer toughness were successfully prepared.

中文翻译：

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层压压制和微波烧结制备WC晶粒尺寸和Co成分梯度分布的WC-Co硬质合金

摘要 通过球磨WC和Co粉末混合物不同时间制备了不同粒径和Co含量的WC-Co复合粉末。通过层压压制不同的 WC-xCo (x = 10, 15, 20) 粉末混合物和微波烧结层状压块，制备了具有 Co 含量和 WC 晶粒尺寸梯度的功能梯度 WC-Co 硬质合金。WC-xCo 粉末混合物通过 X 射线衍射 (XRD) 和场发射扫描电子显微镜 (FE-SEM) 进行表征，并通过 XRD 和 FE 研究功能梯度硬质合金 (FGCCs) 的相组成和微观结构-SEM 结合能量色散光谱 (EDS)。测量了层状 WC-Co 材料的力学行为，并与具有单一成分的 WC-Co 硬质合金的力学行为进行了比较。结果表明，研磨时间从 6 小时增加到 24 小时，导致 WC-Co 复合粉末的粒径从 0.31 微米减小到 0.11 微米。在层压压制和微波烧结后，WC-Co 样品几乎完全致密，相对密度高于 99.7%，在 FGCC 中未检测到 ƞ 相。FGCC 中的 Co 含量和 WC 晶粒尺寸从核心向表面减小。Co的均匀化几乎没有发生，烧结样品的层间没有形成裂纹。在内层中，平均 WC 晶粒尺寸为 529 nm，而在外层中仅为 274 nm。由于 Co 含量和 WC 晶粒尺寸的差异，FGCC 表面的洛氏硬度为 90.75 HRA，而在芯部降低到 86.75 HRA。然而，断裂韧性从 11 增加。53 在表面到 18.12 MPa m -1/2 在核心。目前的结果表明，成功制备了具有高外层硬度和高内层韧性的 FGCC。