Microstructure evolution and phase transformation during spark plasma sintering of Ti(C,N)-based cermets

Ti(C,N)-based cermets were prepared by spark plasma sintering (SPS) at different temperatures and with different soaking durations. The microstructure evolution and phase transformation were studied by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction analysis (XRD). It was found that the microstructures of the cermets prepared by SPS contained many grains with the typical “core-rim” structures, which were believed to form by Ostwald ripening mechanism. During the SPS sintering, with increasing sintering temperature and soaking duration, the number of small ceramic grains decreased and the thickness of the rim phase increased. The contents of Ti, Mo and W atoms in the binder phase also increased. However, the contents of Mo and W of the carbonitride reduced with increasing temperature below 1623 K and increased markedly from 1623 K upwards to 1673 K. (Ti,Mo,W)(C,N) solid solution has formed below 1473 K by the dissolution of small grains and reprecipitation on large ones.