Abstract Hard metals are metal matrix (typically cobalt) composites that tungsten carbide particles operate as reinforcement. These composites are also known as cemented carbides. Cobalt is the traditional option for binder in the production of hard metals and nowadays over than 90% of all hard metals based on WC, preferably exploit Co as metallic glue with approximately 3-30 wt.%. In this study, in order to consider the influence of tungsten carbide’s particle size and quantity on hard metals properties, different composition of tungsten carbide powder by dimensions such as 55 nanometer and 3 micrometer and cobalt powder with under 3 micrometer particle size were provided. Powder mixtures were placed under operation of ball-mill for 1 hour. Then the mixed powders are lied at a temperature of 1200° C and a pressure of 40 MPa for 15 minutes under spark plasma sintering.The Archimedes density measured and the microstructure of specimens were considered with SEM and Eventually, the hardness test done. Considering a mixture of tungsten carbide powder in two scales such as nano and micro could reach a higher hardness and density rather than the case using tungsten carbide powder only in micro scale. But the added percentage of nano powder has an optimal value, and if it goes beyond this optimum can result in loss of hardness and density. With adding this optimum nano tungsten carbide powder can rich to near theoretical density and the hardness of 84HRA.

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