Role of iron addition in the combustion synthesis of TiC–Fe cermet

Coarse iron powders were incorporated into a mixture of titanium and carbon black powders, and the mixture was used for a combustion front quenching test. The quenched sample was analysed by scanning electron microscope (SEM) and energy dispersive X-ray (EDX) analysis to study the microstructural evolution in the iron powders. Also, the phase constituent of the combustion-synthesized product was analysed by X-ray diffraction (XRD). The results showed that the microstructural evolution in the iron powders could be described by the solution–precipitation model. Diffusion of carbon into the iron powders brought about a decrease in the melting point of the Fe–C alloy and a melt of the Fe powders, thus accelerating the solution of Ti into the molten droplets; then, TiC particles precipitated out of the saturated droplets. Therefore, it was suggested that iron addition mainly played the role of a source of reaction, i.e. it not only made necessary preparations for the combustion reaction of Ti + C, but also it provided another source for the precipitation of TiC particles.