Microstructure Evolution, Structural Integrity, and Hot Corrosion Performance of Nitrogen-Enhanced Stainless Steel Welds

Abstract

This work articulated the multi-pass, gas tungsten arc welding by adopting pulsating current for joining nitrogen-enhanced, low-carbon austenitic stainless steel, AISI 316L(N). An austeno-ferrite stainless steel (ER2594) and an over-alloyed (ERNiCrMo-3) fillers were employed to join 6-mm-thick plates of AISI 316L(N). Acicular and lathy ferrite in the weld zone of ER2594 and the occurrence of secondary phases in the fusion zone of over-alloyed filler were observed. The notch tensile strength data attested that the joint strength was greater for the welds employing an over-alloyed filler. This study also affirms that the welds obtained with ER2594 filler resulted in better impact toughness (144 J) compared with ERNiCrMo-3 filler and base metal. Also the notch impact toughness of ER2594 weldment is increased to 60% in comparison with that of candidate metal. Corrosion studies were also performed by exposing the coupons in a eutectic salt mixture comprising of 40%K{sub 2}SO{sub 4}-60%NaCl for 50 cycles at 650 °C. It is observed that the weld zone employing over-alloyed filler experienced better high-temperature corrosion resistance compared to the base metal. The specific results of this investigation will be of greater demand to the nuclear and marine applications utilizing these joints.