Structure Formation in Ti-C-Ni-Mo Composites during Reactive Sintering

Reactive sintering is a novel process where synthesis reaction of the carbide phase is combined with solid and liquid phase sintering of the cermet during a single heating cycle. Ti-C-Ni-Mo composites were synthesized in situ from elemental powders of Ti, Ni, Mo and C by high energy milling, followed by reactive sintering. The milled powders with the grain size in nano-scale were pressed to compacts and sintered. During the sintering that was performed after pressing, the titanium carbide was formed first and then the TiC-NiMo cermet was sintered in the presence of liquid phase in one cycle. The interface between the binder phase and the carbide grains of the in situ composite has a good bonding strength because it is not contaminated with oxidation film or other detrimental surface reactions. The microstructure of such cermet is fine-grained and more homogeneous than that of cermets produced by conventional method. In the paper the phase evolution, microstructure formation and carbide grain growth during reactive sintering are explained.