Abstract Ultrafine WC–Co cemented carbides with Co gradient were prepared by one-step (1300 °C/5 min) and two-step (1300 °C/3 min→1200 °C/5 min) spark plasma sintering. Effects of Co gradient and sintering process on the microstructure and mechanical properties were studied. The higher Co content of core layer provides the good fracture toughness and transverse rupture strength for graded cemented carbides, while the grain growth of surface caused by the migration of Co from the interior to the surface results in a slight decrease of surface hardness. Two-step sintering inhibits the grain growth and improves comprehensive mechanical properties of graded WC–4Co/WC–12Co/WC–4Co cemented carbide. Its surface grain size, hardness, fracture toughness and transverse rupture strength are 231 nm, 2080 kg/mm2, 8.93 MPa·m1/2 and 1829 MPa, respectively. In addition, the cutting performance of graded cemented carbides prepared by two-step sintering was investigated. The graded WC–4Co/WC–12Co/WC–4Co cemented carbide tool has a high wear resistance due to the high surface hardness, and its cutting edge has a good resistant capacity against breakage due to the high internal strength. It presents the longer tool life and higher machined surface quality than commercial YG8 tool.

中文翻译：

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一级/二级放电等离子烧结分级超细WC-Co硬质合金刀具的制备与性能

摘要 采用一步（1300 °C/5 min）和两步（1300 °C/3 min→1200 °C/5 min）放电等离子烧结法制备了具有Co梯度的超细WC-Co硬质合金。研究了钴梯度和烧结工艺对显微组织和力学性能的影响。芯层较高的 Co 含量为梯度硬质合金提供了良好的断裂韧性和横向断裂强度，而 Co 从内部迁移到表面引起的表面晶粒长大导致表面硬度略有下降。两步烧结抑制了晶粒长大并提高了梯度WC-4Co/WC-12Co/WC-4Co硬质合金的综合力学性能。其表面晶粒度、硬度、断裂韧性和横向断裂强度分别为231 nm、2080 kg/mm2、8.93 MPa·m1/2和1829 MPa。此外，研究了两步烧结制备的梯度硬质合金的切削性能。分级WC-4Co/WC-12Co/WC-4Co硬质合金刀具由于表面硬度高而具有较高的耐磨性，其切削刃由于内部强度高而具有良好的抗断裂能力。与商用 YG8 刀具相比，它具有更长的刀具寿命和更高的加工表面质量。