Effect of Electrodes and Post Weld Solution Annealing Treatment on Microstructures, Mechanical Properties and Corrosion Resistance of Dissimilar High Nitrogen Austenitic and Conventional Austenitic Stainless Steel Weldments

Abstract

In the present investigation, the dissimilar metal butt joints between low nickel high nitrogen 201 stainless steel and conventional 304 stainless steel were prepared by shielded metal arc welding process with two different fillers, E308L and E309L. The effects of fillers, along with variation in solution annealing temperature as 1050℃ and 1100℃, on the microstructural characteristics, mechanical properties, and intergranular corrosion behaviour of dissimilar weldments were investigated. The primary δ-ferrites of fusion zone were transformed into austenite at the solution annealing temperature for both the fillers and the transformation rate was accelerated with the increased solution annealing temperature. This led to a reduction in the ferritic-austenitic interface and subsequently improved the corrosion resistance. The double loop electrochemical potentiodynamic reactivation test was performed to measure the degree of sensitization. The fracture surface examination of weldments revealed the presence of a fibrous structure before the solution annealing treatment and demonstrated a ductile failure. After the solution annealing treatment, the ferrite to austenite transformation treatment led to a river like morphology and indicated for brittle fracture.

Fig. 7 SEM micrographs of AR and SA fragmented specimens for (a), (b) and (c) for E308L filler and (d), (e) and (f) for E309L fillers respectively.