Microstructure, pitting corrosion and tensile properties of dissimilar and similar stainless steel gas tungsten arc welds

Abstract

In this work, microstructure and tensile properties are correlated with pitting corrosion of dissimilar and similar gas tungsten arc (GTA) welds of austenitic stainless steel (AISI 304) and ferritic stainless steel (AISI 430). Aim of the work is to determine the effect of two filler metals namely, austenitic stainless steel (AISI 308) and ferritic stainless steel (AISI 430) on microstructure, tensile properties and pitting corrosion of GTA welds. Three regions of weldments, fusion zone, heat affected zone (HAZ) and base metal were tested for pitting corrosion using potentio-dynamic polarization test in 3.5% NaCl environment. Tensile tests were carried out and failure locations were recorded. Optical microscopy was carried out on all weldments before and after corrosion testing, so as to correlate the microstructure and mechanical properties with the corrosion behaviour. In both dissimilar and similar stainless steel joining, welds made with austenitic filler wire were found to be having improved strength with good ductility when compared to that of welds made with ferritic filler wire. Relatively higher number of corrosion pits was observed in welds made with ferritic filler wire resulting in poor corrosion resistance. Comparison of pitting potentials across the dissimilar welds shown clearly that relatively higher positive potentials were obtained with austenitic filler resulting in better corrosion resistance. Hence, from present study it can be concluded that austenite filler wire is best suited for both dissimilar and similar stainless steel welding in terms of both strength and pitting corrosion resistance.