Microstructure and Properties of Dissimilar Joints of AISI 430 Steel with Inconel 625 Obtained by Electron Beam Welding

Electron Beam Welding (EBM) is a high-energy density fusion process where joint is bombarded to be welded with strongly focused beam of electrons. This method is often used for advanced materials and complex, critical parts, like turbine rotors, but it can also be used for many simpler processes involving large production runs. It is very suitable for butt welding materials of different thicknesses. The aim of this work was to study the microstructure, hardness, and electrochemical corrosion behavior between the dissimilar welds were investigated. Electron Beam Welding of dissimilar steel alloys Inconel 625 and AISI 430 was studied. In welding process there was used only welded materials without filling material. Results showed the microstructure of the weld solidified in dendritic morphology. The microstructure of fusion zone showed that dendrites grew in different directions for each grain. The dendrites and columnar grains are mainly exposed to the fusion boundary with some equiaxed grains. The hardness of the overall joint was non-uniform. The highest hardness of the HAZ/Inconel 625 (the heat-affected zone) was 258 HV, and the lowest weld zone hardness was 178 HV. The decrease in weld hardness may be due to the linear welding energy, which led to grain growth and excessive cooling. HAZ/AISI 430 steel has the lowest current density and the highest corrosion potential. Steel has a more negative corrosion potential and a lower corrosion current density than joints, likely due to higher levels of chromium. In this study, a metallographic investigation of the joints revealed no defects such as microcracks or pores. The melting temperatures of the two materials were quite different, but with the help of gravity, stainless steel acts as a permanent joint, like a rivet.