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

Abstract

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 diff erent 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 fi lling material. Results showed the microstructure of the weld solidifi ed in dendritic morphology. The microstructure of fusion zone showed that dendrites grew in diff erent 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-aff ected 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 diff erent, but with the help of gravity, stainless steel acts as a permanent joint, like a rivet.

Combined titanium-steel structures formation by directed energy deposition using vanadium and nickel interlayers

“…Nevertheless, in some studies the formation of such a structure was avoided by rapid cooling from the liquid state [17][18][19]23]. To overcome this problem, an additional layer between vanadium and iron layers, for example, copper was used [15] or nickel, which is well welded with most iron-based alloys [27][28][29][30][31][32][33]. However, a layer of pure copper signi cantly impairs corrosion resistance and reduces the whole structure strength due to the low strength properties of copper [34][35][36][37][38][39][40].…”