Plate-crystalline tungsten carbide-containing hard alloy, composition for forming plate-crystalline tungsten carbide and process for preparing said hard alloy

A plate-crystalline tungsten carbide-containing hard alloy which comprises:

• (a) 4 to 40% by volume of a binder phase containing at least one of iron group metals selected from the group consisting of cobalt, nickel and iron as a main component;
• and
• (b) the balance of a hard phase comprising
• (i) tungsten carbide alone, or
• (ii) tungsten carbide and 50% by volume or less of a compound with a cubic structure selected from at least one of carbide and nitride of the 4a group element of the periodic table selected from the group consisting of titanium, zirconium and hafnium, 5a group element of the periodic table selected from the group consisting of vanadium, niobium and tantalum or 6a group element of the periodic table selected from the group consisting of chromium, molybdenum and tungsten and mutual solid solutions thereof, and inevitable impurities,
• wherein said tungsten carbide has an a axis length of 0.2907 nm or more and a c axis length of 0.2840 nm or more in its crystal axis.

A composition for forming a plate-crystalline tungsten carbide, which is a composite composition comprising:

• (a) 50% by weight or more of a composite carbide compound, said composite carbide comprises:
• (i) at least one of cobalt, nickel, iron and chromium,
• (ii) tungsten, and
• (iii) carbon;
• and the balance of:
• (b1) a carbon sources compound of at least one of carbon, graphite and precursors thereof, or
• (b2) said carbon source compound and a composition adjusting compound of at least one of carbide and nitride of the 4a group element of the periodic table selected from the group consisting of titanium, zirconium and hafnium, 5a group element of the periodic table selected from the group consisting of vanadium, niobium and tantalum or 6a group element of the periodic table selected from the group consisting of chromium, molybdenum and tungsten and mutual solid solutions thereof, and metals of cobalt, iron and chromium and mutual alloys thereof,
• wherein said composite carbide compound comprises 60 to 90% by weight of tungsten, 0.5 to 3.0% by weight of carbon and the balance of at least one of cobalt, nickel, iron and chromium.