Effect of trace Y2O3 on microstructure and properties of WC−6Co cemented carbides with inhomogeneous structure
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摘要: 采用低压烧结法制备了不同Y2O3添加量（质量分数）的WC−6Co非均匀硬质合金，并通过扫描电子显微镜、X射线衍射仪、能谱仪、金相显微镜、电子万能力学试验机、硬度计、矫顽磁力仪等设备研究了Y2O3质量分数对WC−6Co非均匀硬质合金微观结构、相成分及性能的影响。结果表明：Y2O3不会对合金相对密度和相组成产生影响；Y2O3与合金中杂质元素硫、氧等形成稳定的化合物，弥散分散于WC晶界，阻碍WC晶粒的融合长大，降低WC晶粒粒度，抑制WC晶粒非均匀结构的均匀化。随着Y2O3添加量的增加，合金的硬度逐渐增加，而抗弯强度呈现出先迅速上升后下降的趋势。Y2O3质量分数为0.048%对WC−6Co非均匀硬质合金性能提升最明显，硬度和抗弯强度分别达到1530 kgf·mm−2和2902 MPa。Abstract: Inhomogeneous structure WC−6Co cemented carbides with the different Y2O3 additions (mass fraction) were prepared by low pressure sintering. The microstructure and properties of the cemented carbides were investigated by scanning electron microscope (SEM), X-ray diffraction analyzer (XRD), energy dispersive spectrometer (EDS), metallographic microscope, electronic universal mechanical test machine, hardness meter, and coercivity magnetometer. The results show that, the relative density and phase composition of the cemented carbides are not affected by Y2O3 addition. Y2O3 forms a stable solid solution with the impurity elements such as sulfur and oxygen, which disperses in the WC grain boundary, hinders the fusion and growth of WC grains, reduces the size of WC grains, and inhibits the homogenization of WC grains in inhomogeneous structure. With the increase of Y2O3 mass fraction, the hardness of the cemented carbides increases gradually, and the bending strength shows a trend of rapid rise and then decline. The optimum properties of the cemented carbides are obtained when the Y2O3 mass fraction is 0.048%, the hardness and bending strength are 1530 kgf·mm−2 and 2902 MPa, respectively.
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Key words:
- Y2O3 /
- WC−6Co /
- cemented carbides /
- microstructure /
- mechanical properties
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图 1 原料粉末显微形貌：（a）WC；（b）Co；（c）供货态Y2O3；（d）研磨态Y2O3
Figure 1. SEM images of the raw materials: (a) WC powders; (b) Co powders; (c) as-supplied Y2O3 powders; (d) lab-milled Y2O3 powders
图 2 添加不同质量分数Y2O3硬质合金金相形貌：（a）0%；（b）0.024%；（c）0.048%；（d）0.072%
Figure 2. Metallographic images of the cemented carbides added with Y2O3 in various mass fraction: (a) 0%; (b) 0.024%; (c) 0.048%; (d) 0.072%
图 3 硬质合金显微形貌及相对应的能谱分析
Figure 3. SEM image and the corresponding EDS analysis of the cemented carbides
图 4 添加不同质量分数Y2O3硬质合金X射线衍射图谱：（a）0%；（b）0.024%；（c）0.048%；（d）0.072%
Figure 4. X-ray diffraction patterns of the cemented carbides added with Y2O3 in various mass fraction: (a) 0%; (b) 0.024%; (c) 0.048%; (d) 0.072%
图 5 添加不同质量分数Y2O3硬质合金显微形貌：（a）0%；（b）0.024%；（c）0.048%；（d）0.072%
Figure 5. SEM images of the cemented carbides added with Y2O3 in various mass fraction: (a) 0%; (b) 0.024%; (c) 0.048%; (d) 0.072%
图 6 添加不同质量分数Y2O3硬质合金中WC晶粒粒径分布：（a）0%；（b）0.024%；（c）0.048%；（d）0.072%
Figure 6. Particle size distribution of WC grains for the cemented carbides added with Y2O3 in various mass fraction: (a) 0%; (b) 0.024%; (c) 0.048%; (d) 0.072%
图 7 添加不同质量分数Y2O3硬质合金的矫顽磁力和显微硬度
Figure 7. Coercive force and hardness of the cemented carbides added with Y2O3 in various mass fraction
图 8 添加不同质量分数Y2O3硬质合金的抗弯强度
Figure 8. Bending strength of the cemented carbides added with Y2O3 in various mass fraction
图 9 添加不同质量分数Y2O3硬质合金的断口形貌：（a）0%；（b）0.024%；（c）0.048%；（d）0.072%
Figure 9. Fracture morphology of the cemented carbides added with Y2O3 in various mass fraction: (a) 0%; (b) 0.024%; (c) 0.048%; (d) 0.072%
表 1 添加不同质量分数Y2O3合金的密度及相对密度
Table 1. Density and relative density of the cemented carbides added with Y2O3 in various mass fraction
Y2O3质量分数 / % 密度 / (g·cm−3) 相对密度 / % 0 14.896 99.80 0.024 14.899 99.82 0.048 14.911 99.90 0.072 14.856 99.53 
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