超粗晶WC-Co硬质合金的制备方法与机理及性能研究

The Preparation,Preparation Mechauism and Properties of Extra Coarse-grained WC-Co Hardmetals

采用加入球磨活化的细WC粉的方法,成功制备了WC截线晶粒度大于6.5μm的超粗晶硬质合金。对制备机理进行了分析,并对所制备超粗晶硬质合金的金相、热导率、断裂韧性和抗氧化性等进行测定。结果表明:活化细粉在固相烧结阶段全部消失,可以增加烧结活性并抑制超粗晶粒溶解、粒径减小;超粗晶硬质合金WC晶粒度分布窄,晶界平直;热导率和断裂韧性是同样钴含量为0.8μm WC-Co硬质合金的两倍以上,具有优良断裂韧性是由于其可以发生塑性变形;在超粗晶硬质合金中添加镍并不能显著提高抗氧化性。

Extra coarse-grained hardmetals with WC linear-intercept grain size of more than 6.5 μm were prepared successfully by adding activated fine WC powders during ball milling. Its metallography, thermal conductivity, fracture toughness and oxidation resistance of these hardmetals were tested. The results indicated that the activated powders, which improved the sintering activity and inhibited extra coarse WC powders dissolution, disappeared during solid phase sintering stage. The grain boundaries of WC with narrow size distribution are straight. Thermal conductivities and fracture toughness are more than two times of 0.8 μm WC hardmetals with the same cobalt content. The favorable fracture toughness was attributed to the plastic deformation of extra coarse-grained harmetals. The oxidation resistance of the hardmetals with addition of nickel hasn＇t significantly improved.