SINTERING AND MICROSTRUCTURE OF NANOPHASE WC CO HARDMETALS/

For improving the mechanical properties of WC/Co hardmetals, the devel opment is in the direction of diminishing scale and increasing uniform ity of the structure, extending into the nanoscale region. Thus, a new approach to produced nanophase WC/Co powder was developed by thermo-c hemical process. It is much more direct route for making WC/Co than tr aditional processing methods, and offers the potential for cost produc tion of novel materials with homogeneous nanophase microstructures and improved properties. However, the major problems of nanophase WC/Co i s coarsing of carbide particle during sintering due to large surface a rea between carbide particle and cobalt phase. To overcome coarsing of WC particle during sintering, transition metal carbide were used as g rain growth inhibitor with different amount respectively. VC, TaC and VC/TaC were effective as grain growth inhibitors to retain nanophase m icrostructure. Nanophase WC/Co doped VC/TaC was shown superior hardnes s and TRS values, and microstructure was maintained ultrafine scale wi th rounded WC particles.