Understanding the role of Ti addition on the corrosion and passive film characteristics of Nb stabilized AISI 347 weld

Abstract

A multipass multilayer weld pad was fabricated on AISI 347 base metal with filler combinations of AISI 321 and AISI 347, to understand the role of Ti addition on metallurgical, corrosion, and passive film characteristics of the AISI 347 weld. Weld layers with Nb content of 0.53 wt.%, 0.47 wt.%, 0.23 wt.% and Ti of 0 wt.%, 0.21 wt.%, 0.33 wt.%, respectively, were extracted from fabricated weld pad. Selected weld metal compositions were subjected to thermal aging at 750°C for 24 h to investigate the influence of varying precipitation induced in these welds. Ti addition in AISI 347 weld showed lower enrichment of C and Cr at dendritic regions resulting in reduced Cr depletion, lower sensitization, enhanced pitting potential, and repassivation ability compared to conventional Nb stabilized AISI 347 weld. Passive film characteristics studied by electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy depicted formation of more protective, and dense passive film with higher Cr, Ni, and O concentrations for Ti added AISI 347 weld relative to conventional ones. Therefore, Ti addition via the use of Ti stabilized filler in the Nb stabilized AISI 347 weld proved to be efficient in enhancing its corrosion performance by forming a more protective passive oxide film. © 2022 Wiley-VCH GmbH.