Comparison of the Stress Corrosion Cracking Behaviour of AISI 304 Pipes Welded by TIG and LBW
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Comparison of the Stress Corrosion Cracking Behaviour of AISI 304 Pipes Welded by TIG and LBW Ji‑Jin Xu1 · Shuai Wang1 · Ze Chai1 · Chun Yu1 · Jun‑Mei Chen1 · Hao Lu1 Received: 28 April 2020 / Revised: 10 June 2020 / Accepted: 14 July 2020 © The Chinese Society for Metals (CSM) and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The stress corrosion cracking (SCC) behaviour of AISI 304 pipe girth welds which were welded by a single-pass laser beam welding (LBW) and a multi-pass tungsten inert gas welding (TIG), respectively, was studied by the slow strain rate tests combined with the electrochemical corrosion tests. The results show that fracture of both the TIG joint and LBW joint occurs in the heat-affected zone (HAZ). According to the electron-backscattered diffraction observation of the microstructures, comparison of potentiodynamic polarization curves and X-ray photoelectron spectroscopy analysis of corrosion products on HAZs of the two joints after the electrochemical tests, the LBW joint exhibits better SCC resistance than the TIG joint in corrosion environments, due to the synthetic effect of more Cr2O3 in corrosion products, finer grains, lower residual strain and higher δ-ferrite content in its HAZ. Although the TIG joint has better mechanical property, considering lower SCC susceptibility and higher production efficiency of the LBW joint, the LBW promisingly replaces the TIG for welding of AISI 304 pipes in the nuclear power industry. Keywords Laser beam welding · Slow strain rate test · Stress corrosion cracking · Tungsten inert gas welding · AISI 304 stainless steel
1 Introduction Due to the excellent weldability, high-temperature performance and corrosion resistance, AISI 304 austenitic stainless steel has been widely used in various fabrication industries as a structural material, especially in the nuclear power industry [1]. Stainless steel pipes made of AISI 304 are commonly welded by using tungsten inert gas (TIG) welding and laser beam welding (LBW). TIG welding is a conventional arc technique and now in widespread use, but requires a complicated multi-pass process when jointing plates with large thicknesses [2]. In contrast, LBW involving Available online at http://link.springer.com/journal/40195. * Ji‑Jin Xu [email protected] * Chun Yu [email protected] 1
Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
a straightforward single-pass process has higher productivity and welding efficiency, lower heat input, smaller heataffected zone (HAZ), deeper penetration and excellent welding quality [3, 4]. It is a well-known fact that corrosion resistance of a welding joint depends mainly on the welding technique used because in a specific welding process, the HAZ inevitably undergoes plastic deformation resulting in the variation of the microstructures and introduction of residual stresses [5]. The effects of LBW and TIG on corrosion behaviour
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