Influence of high gas pressure on combustion synthesis of the solid–solid reaction of NiAl compound

We show the advantage of using high gas pressure in the improvement of combustion synthesis conditions for NiAl compound synthesis. Experiments on high pressure of argon between 10 and 500 MPa showed that the exothermicity of Ni–Al reactions was considerably reduced, with a complete reaction giving NiAl compound. Thermodynamic and kinetic studies were carried out. The results indicate that pressure has relatively little influence on heat capacity or on the enthalpy of the reaction. We show that high pressure lowers the exothermicity of the reaction primarily by increasing the thermal conductivity of the sample. We propose an evolution of thermal conductivity as a function of pressure in the range 10–500 MPa. The main interest of this study is a pressure–heating rate diagram developed for self-propagating high-temperature synthesis (SHS) of NiAl.