一步还原包裹粉工艺制备WC-Co超粗硬质合金

Ultra-coarse Grain WC-Co Cemented Carbide from Chemical Coated Powder by One-step Hydrogen Reduction

摘要:

以费氏粒度为4.1μm的WC粉末和CoCl2?6H2O、(NH4)2C2O4?H2O为原料，将钴粉制备过程与粉末混合过程相结合，一步还原制备WC-Co包裹粉，并以包裹粉为原料成功制备了WC-8w%o超粗硬质合金。借助扫描电镜、X射线衍射仪、化学元素分析仪、力学试验机等对WC-Co复合粉末及硬质合金的微观形貌、物相组成和性能进行表征与分析。结果表明，一步还原法制备的WC-Co包裹粉末中，Co为fcc和hcp双相结构，Co相呈树枝状包裹在WC粉末表面。由该包裹粉制备的硬质合金组织结构均匀，综合性能优异，合金平均晶粒尺寸为8.9μm，密度14.63g?cm-3，硬度87.6HRA，抗弯强度2438MPa，断裂韧性20.92MPa?m1/2。一步还原包裹粉工艺克服了传统湿磨工艺混料过程中WC粒度显著减小的问题，晶粒度可控性好，且工艺流程简单，有潜在的工业应用价值。

Abstract:

The ultra-coarse grain WC-8w%Co cemented carbide with an average grain size of 8.9μm was prepared from WC-Co chemical coated powders produced by merging the preparation of Co powder with the mixing of WC and Co. The tungsten carbide powder with Fiss particle size of 4.1μm, cobalt chloride and ammonium oxalate were used as the raw materials. Microstructures，phase constitutes and properties of composite powders as well as cemented carbides were characterized by Scanning electron microscopy (SEM), Chemical element analysis, X-ray diffractometry (XRD) and so on．The results shows that, in the WC-Co chemical coated powders, cobalt exists in fcc and hcp structure and exhibits the irregular shapes on the surface of WC particles. The cemented carbide prepared from carbide WC-Co chemical coated powders has a homogeneous microstructure and excellent mechanical properties while density, hardness, transverse rupture strength and fracture toughness is 14.63g?cm-3，87.6HRA, 2438MPa and 20.92 MPa?m1/2,respectively.The chemical coated method does not only overcome the defect of wet mixing reducing WC grain size remarkably, but also has advantage of low cost and simple technological process.