Welding of NiAl by Self-Propagating High-Temperature Synthesis Reaction between Droplet and Powder

A new welding method was proposed based on the self-propagating high-temperature synthesis (SHS) reaction between droplets and powder of elemental metals, and its feasibility was investigated in a simple experiment. In the experiment, an aluminum droplet was dropped onto nickel powder heaped up in a groove at the interface between two NiAl substrates. The aluminum and nickel exothermically reacted and produced intermetallic compounds in Al-Ni system, and the NiAl substrates near the interface were melted by the heat from the reaction. The microstructure of the reaction products varied depending on the initial temperatures of the aluminum droplet and nickel powder and also the groove spacing. Increase in initial temperatures of the aluminum droplet and nickel powder and the groove spacing promoted both the exothermic reaction to synthesize NiAl in the groove and the melting of the joint surface of the substrates