Study On Injection Molding Process Of JD8-3 Cemented Carbide

Metal injection mo lding(MIM) is the fastest growing technology within the powder metallurgy area. The reason for this growth is that it is an efficient production method. Compared to pressing molding MIM can be used to shape parts with higher complexity, good precision and better mechanical properties. JD8-3cemented carbides powder has been discovered by own laboratory, which has been widely used with ultrafine grain and good mechanical properties. The author aims at discovering MIM technology used in JD8-3through the selection of binders, debinding process, sintering process etc.The results showed that the pw-based binder system:PW74%、EVA19%、 HDPE5%、SA2%can fulfils the demand of MIM by making feed with good rheological property, and the suitable solid loading is58%. The zero defect B standard bending specimens have been made via the study of injection technology, and the best injection pressure, the best injection temperature and holding pressure are95MPa,150℃and85MPa.The debinding process of JD8-3cemented carbides injecting green bodies was been studied by single thermal debinding and "solvent debinding+thermal debinding", the results showed that single thermal debinding process easily made debinding defects and costed longer time, while "solvent debinding+thermal debinding" was efficient to dislodge binders with no influence on the carbon content of samples. During the solvent debinding process, the best debinding temperature and time with n-heptane is40℃,4h. In order to decrease the defect of injecting green bodies and improve the production efficiency, the samples were sintered with thermal debinding and sintering one system furnace after solvent debinding. It’s better to remove the binders and control the carbon content of greens at450℃and hold for150min. During the liquid phase sintering process, with the2℃/min rate to heat up to1430℃and hold for90min obtained the ultrafine grain WC, in which the minimum size is651.3nm. Finally the good properties JD8-3cemented carbides injecting specimens are achieved, and the density, flexural strength and vickers hardness are14.43g·cm-3,1754MPa and2132HV30.After the comparison of JD8-3injection molding and pressing molding, the mechanical properties of JD8-3injecting samples reached the standard of pressing molding. The conical gears were made by using JD8-3powders with MIM, the product has good properties, and has already reached high level with the14.42g·cm-3density and2019HV30vickers hardness, which indicated that the JD8-3powders can be used to produce cemented carbides parts with high complexity through MIM.