Metallurgical Behavior and Corrosion Performance of Ti + Nb Stabilized Austenitic Stainless Steel Welds

Abstract

The effect of stabilizing additions of Ti and Nb on corrosion performance of austenitic stainless steel welds was studied. Multipass multilayer austenitic stainless steel weld pads comprising filler combinations of AISI 316L, AISI 347, and AISI 321 were fabricated and different weld compositions were obtained from these weld pads. Among all weld metals, as-deposited weld with Ti content of 0.12 wt.% and Nb content of 0.48 wt.% exhibited the lowest degree of sensitization and superior pitting corrosion performance in contrast to other Ti + Nb stabilized, Nb stabilized and AISI 316L deposited welds. Thermal aging at 750 °C for 24 h increased corrosion susceptibility for different welds where the presence of Ti and Nb in austenitic stainless steel weld facilitated higher Ni retention characteristics and lesser Cr depletion at dendritic regions as compared with Nb stabilized and AISI 316L deposited weld metals. The passive film formed on Ti + Nb stabilized weld was relatively thinner (3.61 nm) and denser by virtue of the presence of higher content of Ni, Cr, and O that enhanced its passive film protectiveness as determined from electrochemical impedance spectroscopy results. Thus, Ti and Nb played a combined role in lowering the segregation of vital elements such as Cr, C, Ni in austenitic stainless steel welds thereby improving their corrosion performance. © 2022, ASM International.