One step synthesis and densification of ultra-fine WC by high-frequency induction combustion

Dense WC with grain size of 0.43 mu m was synthesized by high-frequency induction combustion synthesis from milled elemental powders of W and C. The milled W powders had a grain size in the range 45-73 nm. Dense product (98.5%) could be obtained within 2 min under a pressure of 60 MPa. Due to loss of carbon (by interaction with surface oxides), products made from stoichiometric powders (W:C = 1: 1) contained the sub-carbide W,C. With excess carbon, products containing the WC phase only were obtained. The effect of initial grain size (of W) and the W:C stoichiometry on the grain size of the product WC was investigated. The grain size of WC increased with an increase in the amount of excess carbon. The maximum values for fracture toughness and hardness obtained for the dense WC were 4.8 MPa m(1/2) and 2708 kg/mm(2), respectively. (C) 2005 Elsevier Ltd. All rights reserved.