Heat generation and heat transfer during reactive joining of NiAl to steel

Numerical modelling of heat generation and heat transfer during reactive jo ining of NiAl to steel was carried out based on a calculation of an exother mic reaction Ni + Al --> NiAl and heat transfer analysis by a finite differ ence method. Reactive joining is a new method to synthesize a bulk intermet allic compound and to simultaneously join it to a base material, based on s imple pouring of elemental liquids onto the base material. The base materia l is melted at the joint interface due to the heat of formation of the comp ound, which results in a good join. The depth of the melted steel increases with the increase in thickness of the synthesized NiAl, pouring temperatur es of nickel and aluminium and preheating temperature of the steel. However , the increase in depth of the melted steel is halted when the thickness of the NiAl exceeds a critical value, due to the increase in convection heat transfer and radiation to the surroundings. It was found that the steel was melted without preheating, due to the large amount of heat from the synthe sized NiAl. The calculated results agreed well with the results of the expe riment carried out to examine the validity of the numerical modelling.