Microstructure evolution and reaction mechanism during reactive joining of TiAl intermetallic to TiC cermet using Ti–Al–C–Ni interlayer

This study reports on a new approach for joining of TiAl intermetallic to TiC cermets by self-propagating high-temperature synthesis. The adiabatic combustion temperature in the Ti–Al–C–Ni system was calculated and the composition of the reactants was determined by the calculated result. For a typical microstructure of the joint, two continuous grey reaction layers were found near the TiAl substrate and massive Ni-rich zones were observed adjacent to the TiC cermet. It was noted that the voids were inevitable in the reaction products. The crack was always formed at the interface between the interlayer and TiC cermet due to the residual stress. The interfacial joining between TiC cermet and the interlayer depended on the formation of Ni-rich layer. The joining between the TiAl and the interlayer was simplified as the reaction between liquid Al and solid TiAl. The SHS reaction in Ti–Al–C–Ni system was ignited at the melting point of Al. The first reaction took place between liquid Al and solid Ti to form TiAl3. With the increase of the temperature, Ti reacted with C to form TiC phase.