SBIR Phase I: Functionally Graded Cemented Tungsten Carbide -- Process and Properties

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This Small Business Innovation Research (SBIR) Phase I project aims to develop an innovative process to significantly enhance the manufacturability of functionally graded cemented tungsten carbide (FGM WC-Co) by utilizing a high temperature carburization process. This technology is based on the understanding of the thermodynamics and kinetics of liquid phase equilibrium and migration during sintering. The approach is to exploit the thermodynamic equilibriums among liquid Co phase and other phases and the dependence of the equilibrium on temperature and carbon content. Co gradient is formed in this process by forcing liquid Co to flow from the surface region towards the interior region during carburizing heat treatment of conventional liquid-phase-sintered WC-Co. The broader/commercial impact of this project will be the potential to develop a high-manufacturability process for FGM WC-Co. Cemented tungsten carbide, WC-Co, is one of the most widely used tool materials in metal machining, mining, oil, gas, geothermal energy explorations, and other industrial applications where extreme wear resistance is required. FGM WC-Co materials are made of WC-Co composites with varying cobalt compositions from surface to the interior of the material. Compared to conventional homogeneous WC-Co, FGM WC-Co offers a combination of superior wear resistance, fracture toughness, and strength, thus provides much more desired engineering performance. However, manufacturing FGM WC-Co presents a difficult challenge because liquid phase sintering, by which most WC-Co products are made today, produces homogeneous materials. This project targets on the development of a new process that can be used to manufacture FGM WC-Co in an economically viable manner.