Step Reduction Method (w-ti-ta-nb) C Composite Carbide

Complex carbide materials were used in cemented carbide widely because of their high melting point,high hardness and strength,high wear resistance, low thermal expansion cofficient, excellent resistance to oxidation and corrosion. Preparation of complex carbide materials has become an important part of cemented carbide research. One-step reduction method were used to synthesize (W-Ti-Ta-Nb)C complex carbide materials and the influence factors of the synthesis process were studied.The (W-Ti-Ta)C powder through solid-solid reaction among W powder, TiO₂, Ta₂O₅, and carbide has been prepared successfully by one-step reduction. The manufacture of (W-Ti-Ta)C powder is studied by single factor analysis method and the best carbonization technology is displayed: calcining temperature is 2100℃, calcining time is 50 mins. The final product produced a content of sosoloid phase as 100%, a content of combined carbon as 10.16%, a content of free carbon as 0.19%.The preparation of (W-Ti-Ta-Nb)C powder by solid-solid reaction between W powder, TiO₂, Ta₂O₅, Nb₂O₅ and carbide was studied. The mechanism of process and the process condition's effort to the index was analysed. It shows that both the content of solid solution phase and combined carbon are increased, and the free carbon is decreased with high calcination tempreture and long calcination time. The manufacture of (W-Ti-Ta-Nb)C powder was studied in detail by orthogonal experiments and analysis of variance and the best carbonization technology is displayed: calcining temperature is 2100℃, calcining time is 50 mins, mixing time is 3h. The final product produced a content of sosoloid phase as 100%, a content of combined carbon as 10.67%, a content of free carbon as 0.15%.Mechanism of solid solution has been studied and the results show that in the system of (W-Ti-Ta-Nb)C,all of TiC, TaC, NbC are cubic crystals except WC. When increase temperature WC changes from hexagonal crystal to cubic crystals and spread to other cubic crystals of the system.It is approved that one-step reduction methed is suitable for preparation of (W-Ti-Ta-Nb)C with cheap shortly process, easily controlled course, high stability and so on.