Two reactant systems for self-propagating high-temperature synthesis of tungsten silicide

Tungsten silicide (WSi 2 ) intermetallic was prepared via self-propagating high-temperature synthesis (SHS) from two reactant systems: one using scheelite (CaWO 4 -Si-Al) and the other pure oxides (CaO-WO 3 -Si-Al). The equilibrium compositions of the reactions were calculated by a standard Gibbs energy minimization. Reactant mixtures were high-energy milled for durations of 0.5, 2, 4, and 8 h and the effects of milling on the synthesized products were studied. The effects of the sand mold on the products were also studied. The phase constituents and microstructural morphologies of the products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray (EDS) capability. Intermetallic WSi 2 was successfully synthesized from both systems. The system that contained the pure oxide (CaO-WO 3 -Si-Al) reactant gave a higher yield of WSi 2 than the system that contained scheelite (CaWO 4 -Si-Al) but the yield from the CaWO 4 -Si-Al reactant system could be optimized by increasing the proportion of Si in the system. The sand mold helped the phase separation of the oxide slag and the intermetallic.