Dual-scale and dual-morphology WC grained WC-8Co cemented carbides comprising triangular or hexagonal fine WC grains and plate-like coarse WC grains were synthesized by vacuum sintering using Co, flaky graphite, WC, and coarse W as the starting materials. The effects of fine WC particle sizes on microstructure, relative densities, and mechanical properties of the dual-scale and dual-morphology WC grained cemented carbides were investigated. The results revealed that the growth of plate-like coarse WC grains was further promoted with the decrease in the particle size of the added fine WC; hence, their aspect ratio increased. In addition, added fine WC led to the separation of plate-like coarse WC grains so as to break their oriented arrangement and prevent their face contact; hence, plate-like coarse WC grains were completely covered by the Co binder phase. Moreover, the addition of smaller particle size of fine WC contributed to more uniform Co binder phase. When 0.4-μm WC powders was added, the aspect ratio of plate-like coarse WC grains was greater than that of plate-like WC grained cemented carbides without the addition of fine WC. The dual-scale and dual-morphology WC grained cemented carbides by adding 0.4-μm fine WC exhibited good comprehensive mechanical properties, with a transverse rupture strength of 3645 MPa, a Rockwell hardness of 91.5 HRA, and a fracture toughness of 12.3 MPa∙m^1/2.

以Co，片状石墨，WC和粗W为原料，通过真空烧结合成了由三角形或六边形细WC晶粒和板状粗WC晶粒组成的双尺度双形态WC晶粒WC-8Co硬质合金。研究了细小的WC粒度对双尺度和双形态WC颗粒硬质合金的微观结构，相对密度和力学性能的影响。结果表明，随着添加的细WC的粒径的减小，板状粗WC晶粒的生长被进一步促进。因此，它们的长宽比增加了。另外，添加细的WC导致片状粗WC颗粒的分离，从而破坏了它们的定向排列并防止了它们的面接触。因此，板状的粗WC晶粒被Co粘结相完全覆盖。而且，添加较小粒度的细WC有助于Co粘结剂相更均匀。当添加0.4μm的WC粉末时，板状粗WC晶粒的长径比大于不添加细WC的板状WC粒状硬质合金的长径比。通过添加0.4-μm细WC制成的双尺度和双形态WC粒状硬质合金具有良好的综合机械性能，其横向断裂强度为3645 MPa，洛氏硬度为91.5 HRA，断裂韧性为12.3 MPa∙m 板状粗WC晶粒的长径比大于不添加细WC的板状WC粒状硬质合金的长径比。通过添加0.4-μm细WC制成的双尺度和双形态WC粒状硬质合金具有良好的综合机械性能，其横向断裂强度为3645 MPa，洛氏硬度为91.5 HRA，断裂韧性为12.3 MPa∙m 板状粗WC晶粒的长径比大于不添加细WC的板状WC粒状硬质合金的长径比。通过添加0.4-μm细WC制成的双尺度和双形态WC粒状硬质合金具有良好的综合机械性能，其横向断裂强度为3645 MPa，洛氏硬度为91.5 HRA，断裂韧性为12.3 MPa∙m^1/2。