Effect of C particle size on the mechanism of self-propagation high-temperature synthesis in the Ni-Ti-C system

Highlights: → We investigated the effect of C particle size on the self-propagating high temperature reaction mechanism. → Coarse C particle size (>38 μm) resulted in the formation of prior TiCx layer between Ti and C. → Prior TiCx layer control the whole reaction of Ni-Ti-C and domain the reaction kinetics. → The selection of C particle size is the most important factor to fabricate TiC/Ni composite using Ti, C and Ni mixtures. - Abstract: Effect of C particle size on the mechanism of self-propagation high-temperature synthesis (SHS) in the Ni-Ti-C system was investigated. Fine C particle resulted in a traditional mechanism of dissolution-precipitation while coarse C particle made the reaction be controlled by a mechanism of the diffusion of C through the TiCx layer. The whole process can be described: C atoms diffusing through the TiCx layer dissolved into the Ni-Ti liquid and TiC were formed once the liquid became supersaturated. Simultaneously, the heat generated from the TiC formation made the unstable TiCx layer break up. However, with the spread of Ti-Ni liquid, a new TiCx layer was formed again at the interface between spreading liquid and C particle. This process cannot stop until all the C particles are consumed completely.