Evaluating the microstructure and mechanical properties of dissimilar welding between austenitic stainless steel A240-TP. 316 and ferritic low alloy steel A387-Gr. 11

Dissimilar joint of low-alloy ferritic steel and austenitic stainless steel has been widely used in industries. In this study, the austenitic stainless steel A240-TP.316 and low-alloy ferritic steel A387-Gr.11 were welded together by gas tungsten arc welding (GTAW) method with constant and pulsed currents. Two types of filler metals, i.e. ER309L and ERNiCr-3, were used in this investigation. The microstructure of the dissimilar weldment was characterized by conventional metallography using optical and scanning electron microscopes and by energy disperse spectroscopy (EDS). The mechanical properties of test samples were evaluated by tension, charpy impact and microhardness experiments. It was found that the samples welded by pulsed current exhibit relatively higher impact energies mainly due to their lower heat input induction and creation of intense mixing in the welding pool. Consequently, the formation of undesirable microstructural features such as carbon depleted zone, transmission region and unmixed zones were reduced in the pulsed current welded specimens. Among all the filler metals used, the nickel based filler metal was found to be suitable since in this case, the migration of carbon into the welding pool was limited and therefore, the risk of transition region formation as compared with other filler metals decreased.