两步烧结对超细晶WC-4%Co硬质合金微观组织及性能的影响

Influence of Two-step Sintering Method on Microstructure and Performances of Ultrafine-grained WC-4%Co Cemented Carbide

采用瞬时烧结法确定了超细晶WC-4%Co硬质合金在烧结过程中矫顽磁力突变温度,据此设计了该合金两步烧结工艺曲线。采用传统烧结方法和两步烧结方法制备超细晶WC-4%Co合金,研究了两步烧结方法对超细硬质合金的微观组织、力学性能和切削性能的影响规律。结果表明:超细晶WC-4%Co合金矫顽磁力突变的温度点在1 450℃以上。采用传统烧结方法制备的超细晶WC-4%Co合金中WC晶粒的三维形貌为多台阶层状结构,WC晶粒尺寸分布范围宽;两步烧结方法制备的WC-4%Co合金中WC的晶粒三维形貌发育为单层和三棱柱混合结构,WC晶粒尺寸分布范围窄。由于细颗粒WC溶解-析出行为的充分进行,两步烧结方法制备的合金硬度略微下降,断裂韧性有较大幅度提高。铣削试验结果表明:两步烧结制备的超细晶WC-4%Co合金木工铣刀的的抗崩刃性能及铣削寿命高于传统方法烧结的合金产品。

The abrupt temperature of coercive force during sintering process of WC-4%Co cemented carbide was investigated by instantaneous sintering, and the two-step sintering process curve was designed. The WC-4%Co ultrafine grained cemented carbides were prepared using traditional sintering method and two-step sintering method by sinter-HIP furnace. The influence of two-step sintering on microstructure, mechanical properties and cutting performance of the WC-4%Co ultrafine grained cemented carbide was investigated. The results show that the three-dimensional grain morphology of WC has a multi-layered structure using traditional sintering method. For the alloy prepared by the two-step sintering method, the morphology of WC grain has a mixture structure, which contains both single-layer and triangular prism structure. Due to the full WC dissolution-precipitation behavior of fine particles, the hardness of the alloy prepared by twostep sintering method is slightly decreased, while the fracture toughness is greatly improved. The milling experiment results show that the average milling life and stability of WC-4%Co ultrafine grained cemented carbide prepared by two-step sintering is superior to that of conventionally sintered cemented carbide.