混料方式对非均匀硬质合金微观结构及性能的影响

Effect of Mixing Methods on Microstructure and Properties of Inhomogeneous Cemented Carbides

以预烧结高Co细晶球粒(WC-12%Co)以及低Co超粗晶混合粉(WC-8.5%Co)为原料并按质量比3∶7配料制备非均匀硬质合金,采用场发射扫描电镜、金相显微镜、矫顽磁力仪、硬度计、电子万能力学试验机等研究不同混料方式对合金微观结构及性能的影响。结果表明:采用干混及干磨方式混料的合金中形成粗晶WC环绕细晶WC聚集组织的非均匀结构,但同时形成较多Co池,恶化合金性能。采用高强度的湿磨方式进行混料能降低Co池出现的概率,促进Co相及WC晶粒的均匀分布,使合金致密度提高,实现较好的综合力学性能。此外,预烧结细晶球粒中WC晶粒的活性显著降低,可减少球磨活化作用的影响,延缓细晶的长大速度,使湿磨合金保持非均匀结构。

Inhomogeneous cemented carbides were prepared by using pre-sintered higher Co content fine-grained pellets(WC-12%Co) and lower Co content ultra-coarse-grained mixed powder(WC-8.5%Co) as raw materials with a mass ratio of 3∶7.The effects of different mixing methods on the microstructure and properties of the cemented carbides were studied by field emission scanning electron microscope,metallographic microscope,coercive magnetometer,hardness tester,and electro-mechanical universal testing machine.The results show that the cemented carbides mixed by dry mixing and dry milling exhibit an inhomogeneous structure of coarse-grained WC surrounding aggregated fine-grained WC,while more Co pools are formed at the same time,deteriorating the properties of the cemented carbides.However,using high-strength wet milling method for mixing can reduce the probability of forming Co pools,promote the uniform distribution of Co phase and WC grains,improve the density of cemented carbides,and achieve supe-rior comprehensive mechanical properties.In addition,the activity of WC grains in the pre-sintered fine-grained pellets is significantly reduced,which mitigates the effect of ball milling activation,slows down the growth rate of fine grains,and maintains the inhomogeneous structure of the wet-milled cemented carbides.