Effects of N2 content in shielding gas on microstructure and toughness of cold metal transfer and pulse hybrid welded joint for duplex stainless steel

作者：Zhiqiang Zhang, Yuru Han, Xuecheng Lu, Tiangang Zhang, Yujie Bai, Qiang Ma · 发表于：Materials Science and Engineering A · 年份：2023 · DOI：10.1016/j.msea.2023.144936 · 被引用次数：54 · 研究领域：Hydrogen embrittlement and corrosion behaviors in metals、Welding Techniques and Residual Stresses、Advanced Welding Techniques Analysis

The influences of N 2 content in shielding gas on microstructure and impact toughness of different zones in cold metal transfer and pulse (CMT-P) hybrid welded joint of duplex stainless steel (DSS) were systematically studied. The results showed that the N 2 -supplemented in shielding gas significantly facilitated austenite formation (weld root: 39.9%→41.2%, weld filler: 40.5%→43.7%, and heat affected zone (HAZ): 36.4%→39.6%). However, when the N 2 content in the shielding gas exceeded 4%, there was no significant change in austenite content because of reaching the solubility limit of N atoms. In addition, γ 2 precipitated both in the weld root and HAZ but not in the weld filler, which cannot be inhibited by N 2 addition in the shielding gas. Besides, a great number of Cr 2 N and dislocations in addition to γ 2 formed in the HAZ, and the content of Cr 2 N and dislocation significantly increased with the increase of N 2 content in the shielding gas. Furthermore, the HAZ exhibited the lowest toughness in comparison with other zones. In addition, with the increase of N 2 content in the shielding gas from 0% to 6%, the toughness increased first and then decreased, and reached the maximum when 4% N 2 added to the shielding gas as (weld root: 122.0 J/cm 2 , weld filler: 135.0 J/cm 2 , and HAZ: 91.8 J/cm 2 ). According to detailed microstructure analysis and toughness level, Ar+4% N 2 was recommended as the shielding gas to join DSS by using CMT-P welding technique.