Dissolution-precipitation mechanism of self-propagating high-temperature synthesis of TiC-Ni cermet

A mechanism of self-propagating high-temperature synthesis (SHS) of TiC-Ni cermet was studied by means of a combustion front quenching method. Microstructural evolution in the quenched sample was observed using a scanning electron microscope (SEM) with energy dispersive X-ray (EDX) spectrometry, and the combustion temperature and velocity were measured. The results showed that the combustion reaction started with a local formation of a Ti-Ni liquid solution and could be described with a dissolution-precipitation mechanism, namely, Ti, Ni, and C particles dissolved into the Ti-Ni solution and TiC particles precipitated in the saturated Ti-Ni-C liquid solution. The local formation of the Ti-Ni solution resulted from a solid diffusion between the Ti and Ni particles, and it was found that the dissolving rate of Ti particles is higher than the Ni particles. In addition, the combustion synthesis has incompleteness and it was attributed to a usage of the coarser Ni and Ti powders. Again, a model corresponding to the dissolution-precipitation mechanism was drawn, and an ignition temperature of the combustion reaction was prophesied as about 942degreesC. (C) 2004 Elsevier B.V. All rights reserved.