To prepare cemented carbides which had high toughness, WC-10〜25%Ni mixed powders were sintered by Spark Plasma Sintering method. And mechanical properties of sintered products were measured. WC powders with the grain-size 0.5 μm and Ni powders with the grain-size 0.2-0.5 μm were used. Transverse-Rupture-Strength (T.R.S.) was highest, when the weight ratio of Ni was 15%. T.R.S. and hardness of the products was 2300〜2500MPa and HV1500 respectively. Next, when WC-15%Ni mixed powders were sintered, WC powders with the grain-size 6.1 μm and 0.5 μm were mixed. We changed the weight ratio of WC6.1 μm to all WC from 0% to 100%. When the weight ratio of WC6.1 μm increased, relative density of the products increased a little and the hardness decreased, but the T.R.S. was changed little. We thought this was because pores remained in the sintered products.
