WC-Al2O3 Composite Synthesis via Microwave Heating of Mechanical Activated WO3-Al-C Mixture

High cost of tungsten carbide synthesis by high temperature solid-state reaction between elemental tungsten and carbon in controlled atmosphere، persuaded researchers to use of cheaper raw materials such as tungsten oxide and alternative synthesis methods which are lower costly than conventional method. In previous researches، capabilities of mechanochemical and microwave synthesis methods for tungsten carbide formation by reduction-carburization of tungsten oxide have been proved. One of the limitations of these methods is W2C formation، as an undesirable phase، in addition to WC. In the present study، a combined process including mechanochemical processing of WO3-Al-C mixtures followed by microwave heating was employed to accelerate WC-Al2O3 composite synthesis، and effect of milling time and microwave heating on the ratio of WC: W2C in the products have been investigated. The powder mixture with a molar composition of WO3-2Al-C were first treated for 2، 3 and 4 hours in a planetary ball mill، and the pellets which formed by cold pressing of the milled products were then heated in a domestic microwave oven. X-ray diffraction (XRD) analysis on the milled samples showed that، at initial stages of milling، undesirable tungsten semi-carbide (W2C) was formed، while increasing the milling time، improved tungsten carbide (WC) formation and increased the ratio of WC: W2C. Also، microwave heating of the mixture containing 50% excess graphite (WO3-2Al-1. 5C)، after milling for 4 hours، has a significant impact on the progress of tungsten carbide formation reaction so that، the ratio of WC: W2C increased from 4. 7، for the milled sample، to 17. 8، for the milled sample followed by microwave heating.