Microstructure and mechanical properties of WC-based cemented carbides with different binder phases
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摘要: 以碳质量分数为理论含碳量的WC为硬质相，在1450 ℃下通过气压烧结制备WC‒20Fe，WC‒20Ni和WC‒20Co硬质合金，通过X射线衍射、扫描电子显微镜、电子探针和力学性能测试研究了不同金属粘结相对烧结硬质合金微观结构和力学性能的影响。结果表明：WC‒20Fe合金出现η脱碳相（Fe3W3C），W在粘结相Fe中的溶解度仅有1.915%（质量分数），WC晶粒尺寸最小。WC‒20Ni合金渗碳出现石墨相（C），W在粘结相Ni中的溶解度达到10.753%（质量分数），WC晶粒尺寸最大，合金硬度最小。WC‒20Co合金为正常两相区组织（WC+γ），具有最高抗弯强度2720 MPa和最大硬度934.41 kg∙mm‒2。所有合金断裂模式均为脆性断裂和沿晶断裂，WC‒20Co合金断口出现明显的粘结相撕裂。Abstract: The WC‒20Fe, WC‒20Ni, and WC‒20Co cemented carbides were prepared by gas pressure sintering at 1450 ℃ using the WC powders with the theoretical carbon content (mass fraction). The effects of metal binders on the microstructure and mechanical properties of the cemented carbides were investigated by X-ray diffractometer (XRD), scanning electron microscope (SEM), electron probe microanalysis (EPMA), and mechanical properties tester. The results show that, the brittle η-phase (Fe3W3C) appears in the WC‒20Fe alloys, and finer grains are observed due to the lower solubility of W (1.915% by mass) in Fe binder. However, the graphite phase (C) is detected in the WC‒20Co alloys, the solubility of W in Ni binder can reach to 10.753% by mass, resulting in the largest grain size and the lowest hardness. The WC‒20Co alloys show the two-phase region (WC+γ), which exhibit the highest bending strength and hardness of 2720 MPa and 934.41 kg∙mm‒2, respectively. The fracture mode of all the alloys can be described as the brittle fracture and intergranular fracture. Moreover, the fracture surface of the WC‒20Co alloys shows the obvious binder tearing character.
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Key words:
- cemented carbides /
- binder /
- microstructure /
- properties
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图 3 烧结合金X射线衍射图谱局部图
Figure 3. Localized peaks of the XRD patterns for the sintered alloys
图 4 混合粉末显微形貌：（a）WC‒20Fe；（b）WC‒20Ni；（c）WC‒20Co
Figure 4. SEM images of the mixed powders: (a) WC‒20Fe; (b) WC‒20Ni; (c) WC‒20Co
图 5 烧结合金显微形貌：（a）WC‒20Fe；（b）WC‒20Ni；（c）WC‒20Ni；（d）WC‒20Co
Figure 5. SEM images of the sintered alloys: (a) WC‒20Fe; (b) WC‒20Ni; (c) WC‒20Ni; (d) WC‒20Co
图 6 烧结合金断口显微形貌：（a）WC‒20Fe；（b）WC‒20Ni；（c）WC‒20Co
Figure 6. Fracture surface SEM images of the sintered alloys: (a) WC‒20Fe; (b) WC‒20Ni; (c) WC‒20Co
表 1 硬质合金晶粒尺寸和钨在粘结相中的溶解度
Table 1. Grain size of the cemented carbides and the solubility of W in the binder phases
试样 钨在粘结剂中的溶解度
（质量分数） / %WC平均晶粒
尺寸 / μmWC‒20Fe 1.915±0.294 1.29 WC‒20Ni 10.753±0.428 7.07 WC‒20Co 4.583±0.239 2.93 
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表 2 烧结合金物理性能
Table 2. Physical properties of the sintered alloys
试样 相对密度 /
%维氏硬度，
HV10 / (kg∙mm‒2)抗弯强度 /
MPaWC‒20Fe 97.36 886.58 1850 WC‒20Ni 99.23 650.24 1630 WC‒20Co 99.67 934.41 2720
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