Study On The Preparation And The Micro Structure Of Ultra-fine Cemented Carbide

Ultra-fine WC-Co cemented carbide has superior characteristics including excellent hardness and strength which are expected to be widely applicable.In this paper, the ultra-fine WC powder and WC-Co carbide alloy were prepared. In addition, the microstructure of alloy has been researched.Performance of tungsten affected the subsequent deoxidization and the ultimate properties of tungsten powder. So, to select the tungsten oxide precursor was crucial to prepare the ultra-fine cemented carbides. Microstructure of the two precursors, purple tungsten and blue tungsten, and adsorption/escaping curve were compared. On this base, the purple tungsten was chosen as the precursor of tungsten oxide to prepare the powder and carbide alloy.After studying the preparation methods of ultra-fine WC powder, we established an appropriate process to improve the quality of WC powder. We analyzed the process of purple tungsten deoxidization, oriented it, and prepared out the tungsten powder.Then, analyzed the carbonization process of W powder, oriented the carbonization processing, established the carbonization processing through analyzing and comparing the experient, and prepared out ultra-fine WC powder. Some flaws existed in this powder, such as heterogeneous grain size, it is still a paramount direction for synthesis ultra-fine grain size. using the turbo-air stream classifying principle ,we obtained homogeneous super fine WC powder.The factor was studied that influence the densification and shrinkage, including the low-pressure vacuum sintering and inhibitor additions, experimental evidence indicates that Cr3C2 and VC is suitable to as inhibitor additions of ultra-fine cemented carbide. 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 0.3-0.4μm, 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. Using this ultra-fine WC powder prepared by our research group, appending grain growth inhibitor additives, and adopting low-pressure vacuum sintering, we can obtain ultra-fine cemented carbide with small grain size, high strength, and great hardness.Observing the microstructure of ultra-fine cemented carbide sample, the results...