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摘要: 通过富氮气氛烧结WC‒10TiC‒0.5VC‒0.5Cr2C3‒12Co和WC‒12Co硬质合金，研究梯度结构和均匀结构硬质合金的微观结构及力学性能。利用扫描电子显微镜观察合金断面的微观形貌，使用X射线衍射仪和能谱仪分析合金物相组成，并对合金表面和芯部的硬度与断裂韧性进行测试。结果表明：与均匀结构的WC‒12Co硬质合金不同，WC‒10TiC‒0.5VC‒0.5Cr2C3‒12Co梯度结构硬质合金的表层富含立方相TiCN，该表层的厚度大约为12 μm，表层下方是富钴粗晶过渡层。WC‒10TiC‒0.5VC‒0.5Cr2C3‒12Co硬质合金具有表面硬度高、芯部断裂韧性高、WC晶粒细小及分布均匀等优点。Abstract: The microstructure and mechanical properties of the WC‒10TiC‒0.5VC‒0.5Cr2C3‒12Co and WC‒12Co cemented carbides in the functionally graded and uniform structure were systematically investigated by sintering in nitrogen-rich atmosphere. The scanning electron microscope (SEM), energy disperse spectroscope (EDS), and X-ray diffractometer (XRD) were used for the microstructure observation and phase composition analysis, and the hardness and fracture toughness tests were made in both the surface and the center of the cemented carbides. The results show that, different from the WC‒12Co cemented carbides in uniform structure, the surface layer of the WC‒10TiC‒0.5VC‒0.5Cr2C3‒12Co cemented carbides in the gradient structure is rich in TiCN cubic phase, which is about 12 μm in thickness, and there is a cobalt-rich and coarse-grain intermediate layer below the surface layer of the WC‒10TiC‒0.5VC‒0.5Cr2C3‒12Co cemented carbides. Such gradient and ultrafine cemented carbides show the advantage as the high hardness in the surface layer, the high fracture toughness in the core, and the ultrafine and uniform WC grain.
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Keywords:
- cemented carbides /
- gradient structure /
- microstructure /
- grain size
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图 2 渗氮烧结硬质合金表面X射线衍射谱图：（a）合金A；（b）合金B
Figure 2. XRD patterns of the nitriding sintered cemented carbides: (a) alloy A; (b) alloy B
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图 3 硬质合金截面微观组织：（a）合金A；（b）合金B
Figure 3. Sectional microstructure of the cemented carbides: (a) alloy A; (b) alloy B
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图 4 硬质合金芯部微观组织和WC晶粒尺寸分布：（a）合金A微观组织；（b）合金B微观组织；（c）合金A的WC晶粒尺寸分布；（d）合金B的WC晶粒尺寸分布
Figure 4. Microstructure and WC grain size distribution of the cemented carbides in the core: (a) microstructure of alloy A; (b) microstructure of alloy B; (c) WC grain size distribution of alloy A; (d) WC grain size distribution of alloy B
表 1 合金A不同区域能谱分析结果
Table 1 EDS analysis on the surface region of alloy A
位置 质量分数 / % Co Ti W C N 表层 0.87 27.45 54.39 14.71 2.58 过渡层 31.65 5.63 50.08 12.64 0 内部正常组织区域 14.32 15.48 57.75 12.45 0 
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表 2 合金表面和芯部的硬度与韧性
Table 2 Hardness and fracture toughness of alloys A and B (surface and center)
试样 表面硬度，HV30 芯部硬度，HV30 表面韧性 / (MPa·m1/2) 韧性芯部 / (MPa·m1/2) A 1930±35 1755±21 7.65 10.45 B 1650±40 1685±26 11.86 11.63
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