Self-propagating high-temperature synthesis of (Zr,W)C/WC/Al2O3 composite powders from WO3-ZrO2-Al-C system

Abstract

In the present study, the self-propagating high-temperature synthesis of 2(1-x)WO3-3xZrO2-Al-2(1 + 0.5x)C system was considered to prepare WC-ZrC-Al2O3 composite powders. The effects of an increase in the x-value between 0 and 1 as well as the addition of 50 wt% extra carbon to the initial reactant mixture on the adiabatic temperature, reaction front velocity, structure and microstructure of the combustion products were investigated. Results showed that the adiabatic temperature and the reaction front velocity decreased with increasing the x-value until it reached zero for x = 0.5. For x = 0 sample, WC, W2C and W phases were formed after the synthesis process. The addition of extra carbon led to an increase in the (WC + W2C)/W ratio. Furthermore, (Zr,W)C/WC/W2C/Al2O3 composite powders were obtained for x > 0. Moreover, the (Zr,W)C concentration with near-stoichiometric composition and blocky morphology increased with the x-value. Differential thermal analysis results illustrated that the SHS reaction in the WO3-ZrO2-Al-C system is initiated by the aluminothermic reaction of WO3. Moreover, it was postulated that the presence of W facilitated the formation of zirconium carbide.