Control of carbon loss during synthesis of WC powder through ball milling of WO3-C-2Al mixture

Abstract

WC–Al2O3 composite powder potentially could be synthesized through milling of WO3–C–2Al mixture.<br><br>High temperature resulted from reduction ofWO3 by Al, activates the reduction reaction ofWO3 by C and<br><br>brings about carbon deficiency in the system which consequently causes the formation of undesirable<br><br>W2C phase. Hence, addition of excess amounts of C becomes necessary. The aim of the present study<br><br>has been to find out some appropriate routes for the fabrication of WC–Al2O3 composite powder from<br><br>WO3–2Al–C mixtures in such away that the formation ofW2C is prevented. Results of high energy milling<br><br>showed that the mode of reaction inWO3–2Al–C mixture is MSR (mechanically induced self-propagating<br><br>reaction). In this system, evolution of CO gas and high value of C loss were evidences for the need of<br><br>excess C. For samples produced via suggested routes, no CO evolution was observed and the amounts of<br><br>total carbon were constant. These observations showed that the proposed routes have been capable of<br><br>producing WC phase without the presence of W2C. Mechanism of the reactions in each route has been<br><br>discussed.