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

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.

Key words:cemented carbide; ultra-coarse WC grain; hydrogen reduction; chemical coated powders; grain growth