Joining NiAl using simultaneous combustion synthesis and pressure

Abstract

Nickel aluminide-based intermetallics are attractive in applications requiring high thermal stability, corrosion and oxidation resistance, and high-temperature mechanical properties. However, if components are to be produced using these intermetallics, efficient joining techniques need to be developed. This paper provides an initial investigation of the application of combustion (self propagating, high temperature) synthesis (SHS) as a means of joining NiAl intermetallic materials. Combustion synthesis is a technique whereby an exothermic reaction mixture is used to synthesize the required product(s). If the reaction is sufficiently exothermic, it can be self sustaining once initiated at the ignition temperature, Tig. The heat generated by the reaction results in an increase in temperature to a maximum combustion temperature, Tc, which is usually less than the calculated adiabatic temperature, Tad, on account of heat losses from the reaction. Combustion synthesis reactions can be operated in two different modes of ignition, i.e. propagating and simultaneous combustion modes. In each case, the exothermic reactant mix, typically in powder form, is pressed in the required reaction stoichiometry and at a certain green density. In reaction mixtures which are less exothermic, such as the synthesis of an intermetallic compound from its elements, e.g. reaction, the simultaneous combustion mode is oftenmore » used.« less