Characterization of microstructure, mechanical and corrosion response in AISI 304L and Ti-stabilized 439 stainless steels weld joints

Abstract

The gas tungsten arc welding (GTAW) was employed to weld dissimilar materials of 304L austenitic stainless steel (ASS) and Ti-stabilized 439 ferritic stainless steel (FSS). Dissimilar joints were produced using 309L ASS filler electrode with low and high heat inputs (HIs). Austenite and ferrite phases were observed in the weld zone (WZ) of both weldments with varying volumetric fractions. The results showed that the ferrite fraction in WZ decreased with increase in HI from 37.2 % (low HI) to 32.39 % (high HI). Formation of ferrite stringers was observed in the unmixed zone of ASS side, whereas chromium-rich carbides were observed in heat affected zone (HAZ) of FSS side. Higher fraction of carbides was observed for the high HI weldment. Mechanical properties of the low HI weldment were superior to high HI weldment due to higher ferrite fraction. Significant differences in microhardness values were observed for the WZ and HAZ between the two HIs weldments. The electrochemical behaviour of the both the weldments were analysed through the various techniques. The results showed that intergranular corrosion resistance was lower for low HI-WZ than high HI-WZ region, however, opposite trend was observed for impedance and pitting resistance.