Sintering and microstructure of nanophase WC/Co hardmetals

For improving the mechanical properties of WC/Co hardmetals, the development is in the direction of diminishing scale and increasing uniformity of the structure, extending into the nanoscale region. Thus, a new approach to produced nanophase WC/Co powder was developed by thermo-chemical process. It is much more direct route for making WC/Co than traditional processing methods, and offers the potential for cost production of novel materials with homogeneous nanophase microstructures and improved properties. However, the major problems of nanophase WC/Co is coarsing of carbide particle during sintering due to large surface area between carbide particle and cobalt phase. To overcome coarsing of WC particle during sintering, transition metal carbide were used as grain growth inhibitor with different amount respectively. VC, TaC and VC/TaC were effective as grain growth inhibitors to retain nanophase microstructure. Nanophase WC/Co doped VC/TaC was shown superior hardness and TRS values, and microstructure was maintained ultrafine scale with rounded WC particles.