Study On High Quality Ultra-fine WC Powder And Cemented Carbide

Cemented carbide with ultra-fine grain size has superior characteristics including excellent hardness and strength and a high Young's modulus, which encourages their widespread use for cutting tools and wear-resistant tools. Currently, it is widely applied into many fields and found increasing usage in areas such as miniature drills for highly integrated printed circuit boards (PCBs), pins for dot-printers, wood machining, metal machining, dental work, wear parts, etc.Control of the carbide grain size has proved to be critical for optimizing the combination of hardness and toughness of cemented carbides. Methods of grain size control have been development in this area went along lines as follow: Improving the sintering technique, such as optimizing sintering conditions, using pressure during sintering, etc; Using grain growth inhibitors; Using finer starting tungsten and tungsten carbide powders. Although the conventional method of manufacturing ultra-fine cemented carbide exists flaws per se, such as heterogeneous grain size, it is still a paramount direction for synthesis ultra-fine gram size.In this paper, some of the crucial aspects of conventional method that is typical fit for manufacturing ultra-fine cemented carbide are discussed. The microstructure of several precursor of W powder are investigated, with the conclusion that purple tungsten oxide is optimum to obtain high quality super fine WC powder. Subsequently, The process of reduction and carburization of purple tungsten oxide were explored by plenty of experiment and analysis, accompanied by the regulation of parameter. Finally, the optimum parameter of reduction and carburization were founded.Based on the turbo-air stream classifying principle, the quality of superfine WC powder get further improving by means of superfine pulverizing grader. Experiments show that the technology of air steam classifying has significant effect on increase of the fineness and the particle classification efficiency. By comparing different type of air stream equipment, the QYF fluid-bed superfine pulverizing grader was adopted in the experiment that was manufactured by KunShan superfine pulverizers factory as well as obtaining high quality superfine WC powder with high homogeneous.Finally, the factor was studied that influence the densification and shrinkage, including the low-pressure sintering and inhibitor additions, experimental evidence indicates that Cr3C2 and VC is suitable to as inhibitor additions of ultra-fine cementedcarbide. Also, an investigation on the relationship between grain growth and the amount of inhibitor additives was also made. High quality ultra-fine cemented carbide was manufactured with WC grain size lies in the average of 0.3-0.4 um, alloy hardness of higher than 93 and bending strength higher than 3300. The microstructure was found to be composed of very fine and uniform carbides.