Effect of filler and autogenous TIG welding on microstructure, mechanical properties and corrosion resistance of nitronic 50 stainless steel

This paper addresses and compares the effect of filler (ERNiCrMo-4) and the performance of autogenous tungsten inert gas welding process of high concentration nitrogen-based austenitic stainless steel namely Nitronic 50. Weldability of Nitronic 50 in terms of microstructural analysis results, mechanical properties and corrosion behavior are investigated with the help of optical microscopy, scanning electron microscopy equipped with energy-dispersive spectrometer, x-ray diffraction and electrochemical assessment. The observed results indicated that the autogenous and filler weld showed different microstructures because of different chromium and nickel equivalent ratio. Filler (ERNiCrMo-4) based weld showed coarse columnar microstructure of austenite, whereas autogenous weld showed austenitic solidification mode having dendritic microstructure. X-ray diffraction results indicated the presence of carbide and nitride precipitates in both filler and autogenous welds. Higher mechanical properties were measured in the filler and autogenous weld compared to base metal. Higher hardness and tensile strength were obtained in the filler based weld. Pitting and intergranular corrosion resistance of filler based weld was poor compared to autogenous and base metal. Higher weight loss was measured in case of filler based weld.