表层富立方相超细晶梯度硬质合金微观结构

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。

Microstructure of ultrafine graded cemented carbides with cubic rich surface

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.