Tungsten trioxide WO3 is hydrogenated and reduced to prepare tungsten powder (average particle size 3～5μm). Then, the mixture of tungsten powder and carbon black in an equimolar ratio (dry-blended with a ball mill for about 10 hours) is press-formed under a pressure of about 1t/cm2.
Put the pressurized material block into a graphite pan or crucible, and heat it to 1400～1700℃ (preferably 1550～1650) in a hydrogen stream (using pure hydrogen with a dew point of -35℃) using a graphite resistance furnace or an induction electric furnace ℃), carburizing will produce WC. The reaction starts from around the tungsten particles, because W2C is generated at the beginning of the reaction, and because the reaction is incomplete (mainly because the reaction temperature is low), unreacted W and intermediate W2C remain besides WC.
Therefore, it must be heated to the above high temperature. The maximum temperature should be determined according to the particle size of raw tungsten. For coarse particles with an average particle size of about 150 μm, the reaction proceeds at a high temperature of 1550 to 1650°C.
