Welding in Ti–Al and Ni–Al Systems by Self-Propagating High-Temperature Synthesis

The possibility of welding between Ti–Al and Ni–Al layers via self-propagating high-temperature synthesis was demonstrated by using the heat released from the exothermic chemical reaction. The applied pressure and the presence of reactive intermediate layers (Cu, Al) are the most important requirements for strong welding. In the TiAl/NiAl system, there is a temperature gradient, and the main heat transfer occurs toward the Ti–Al layer, resulting in increased Ni diffusion. The increased mobility of Ni atoms is due to their smaller atomic radius as compared to Ti. The proposed technique seems attractive for repair operations and deposition of coatings in special-purpose applications.