Study of diffusion bonding of Fe-28Al alloy with austenitic stainless steel in vacuum

Diffusion bonding of Fe-28Al alloy with Cr18-Ni8 austenitic stainless steel was carried out in vacuum of 10−4 Pa and a diffusion-bonded Fe-28Al/Cr18-Ni8 joint with diffusion reaction layer was formed. Microstructure and reacted phases in the joint were investigated by means of scanning electron microscope (SEM) and X-ray diffractometry (XRD). The reacted phases in the diffusion reaction layer are FeAl, Fe3Al, Ni3Al and α-Fe (Al) solid solution and they may decrease diffusion activation energy of Al, Fe, Cr and Ni to promote element diffusion and even to accelerate the formation of a diffusion reaction layer. The growth of diffusion reaction layer obeys parabolic law and its thickness (y) is expressed to be y2=7.5×10−4 exp(−83600/RT)(t-t0) (mm2). This is favorable to guide the choice of bonding parameters for Fe-28Al alloy with austenitic stainless steel.