Metallurgical investigation of electron beam welded duplex stainless steel X2CrNiMoN22-5-3 with plasma nitrided weld edge surfaces

Abstract

Abstract Duplex stainless steel is common in thick-walled components such as longitudinal welded pipes in the oil and gas industries and as parts of various machines in the chemical and food industries. Electron beam welding is a very suitable method for welding such components. Due to the high power density of the electron beam combined with the decreased evaporation temperature in a vacuum atmosphere, steel with a sheet thickness of up to 150 mm can be welded in one pass. In the case of the electron beam welding of duplex stainless steels, vacuum atmosphere in the working chamber causes a nitrogen effusion from the weld pool. The microstructure of the resulting weld is characterized by an unacceptable high ferrite content, which is the main reason for both low impact toughness and low pitting corrosion resistance. This work focuses on the influence of nitrided weld edge surfaces on metallurgical properties of the resulting welded joint. The aim here is to investigate the effect of increased nitrogen content at the weld edges on nitrogen loss during EB-welding. The welds produced within the experimental work were characterized by means of microstructural analysis and the use of optical and energy dispersive X-ray spectroscopy. It was shown that nitrided weld edge surfaces can compensate nitrogen loss from the weld pool and decrease the ferrite content in the resulting weld.