Characterization of the metal powder suspension to improve the functionality of the cemented carbides
Advancing the chemical engineering fundamentals
Particulate Systems (T2-3P)
Keywords: Particle agglomeration, Cemented carbide, Vertical tube viscometer, Surfactant
Cemented carbide is produced by the sintering of metal carbide granulated powder and now applied to various areas, e.g., cutting, grinding, and polishing. And in order to achieve the product with accurate and complicated figurations and sufficient stiffness, various characteristics including small defects, high density and strong connection between material particles are required. For the improvement in productivity, cemented carbide products are generally produced by the following methods. First, a suspension consists of material powders, solvent, and sometimes additive agent(s) is prepared. Next, granulated powders are produced by the spray-drying of the suspension. And finally, granulated powder are fitted into a mold and then sintered. Hence, the characteristics of the metal carbide granulated powder must directly affect the property of final products. In this study, we characterized the degree of material particle agglomeration in a suspension and investigated the way how to control its characteristics, further clarified the relationships between the characteristics of the suspensions and final products.
Although particle agglomeration in a suspension significantly affects the viscosity of suspension, not only the observation of particle agglomeration but also the measurement of the metal powder suspension viscosity is difficult because of sedimentation of particle and blockage of measurement section. However, a vertical tube viscometer with an enough large inner diameter and much larger flow out velocity than that of settlement will provide considerable valuable results. Therefore, the viscosity of metal particle suspension could be measured by using this viscometer. Further by applying these data to Usui model, which can estimate the interaction and the level of particle agglomeration in a suspension, the effect of the concentration and kind of surfactant on the particle agglomeration was quantitatively evaluated.
And by using the suspension controlling characteristics by the addition of surfactant, the metal carbide granulated powders were produced in a lab-scale and their various properties were measured. The addition of surfactant remarkably affected the shape and size of the granulated powder. And it also implied that there are some relationships between the level of agglomeration and the characteristics of the granulated powder. Viscosity measurement will be a powerful tool in the case of the selection of surfactant corresponding to the metal powder, further the production process may be effectively controlled.
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Presented Monday 17, 13:30 to 15:00, in session Particulate Systems (T2-3P).
