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<p>The present study investigates the microstructural evolution, corrosion behavior, and mechanical response of high nitrogen austenitic stainless-steel (HNS) weldments fabricated using shielded metal arc welding (SMAW) with a near-matching nitrogen-rich consumable. The function of post-weld heat treatment (PWHT) in modifying grain boundary character distribution (GBCD) and improving corrosion resistance is systematically evaluated. Electron backscatter diffraction (EBSD) analyses revealed elongated dendritic grains with heterogeneous grain boundary populations in the as-welded (AW) condition. PWHT promoted static recrystallization, leading to refined equiaxed grains and a significant increase in low-energy Σ3 coincidence site lattice (CSL) boundaries, indicative of enhanced grain boundary engineering. Kernel average misorientation (KAM) analysis confirmed reduced residual plastic strain after PWHT, reflecting effective recovery. Vickers microhardness measurements showed improved uniformity and diminished hardness values in the PWHT due to microstructural homogenization. Electrochemical corrosion studies, performed in 3.5% NaCl solution using potentiodynamic polarization, demonstrated enhanced passivation behavior and lower corrosion current density in the PWHT condition. The enhanced corrosion resistance can be associated to the increased proportion of Σ3 boundaries and reduced dislocation density, which together mitigate preferential corrosion paths. Overall, the study establishes that PWHT enhances the microstructural stability, mechanical uniformity, and corrosion resistance of HNS weldments, making it a promising approach for critical applications in corrosive environments.</p>

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Effect of Matching Electrode and Post-weld Heat Treatment on Microstructural Evolution and Corrosion Resistance of Shielded Metal Arc-welded High Nitrogen Steel

  • 期刊论文

  • 发表日期：

    2025年8月29日

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  • Atmaramudu Tirumalla,
  • Raffi Mohammed,
  • Arun Kumar Gurrala,
  • GMadhusudhan Reddy

摘要

The present study investigates the microstructural evolution, corrosion behavior, and mechanical response of high nitrogen austenitic stainless-steel (HNS) weldments fabricated using shielded metal arc welding (SMAW) with a near-matching nitrogen-rich consumable. The function of post-weld heat treatment (PWHT) in modifying grain boundary character distribution (GBCD) and improving corrosion resistance is systematically evaluated. Electron backscatter diffraction (EBSD) analyses revealed elongated dendritic grains with heterogeneous grain boundary populations in the as-welded (AW) condition. PWHT promoted static recrystallization, leading to refined equiaxed grains and a significant increase in low-energy Σ3 coincidence site lattice (CSL) boundaries, indicative of enhanced grain boundary engineering. Kernel average misorientation (KAM) analysis confirmed reduced residual plastic strain after PWHT, reflecting effective recovery. Vickers microhardness measurements showed improved uniformity and diminished hardness values in the PWHT due to microstructural homogenization. Electrochemical corrosion studies, performed in 3.5% NaCl solution using potentiodynamic polarization, demonstrated enhanced passivation behavior and lower corrosion current density in the PWHT condition. The enhanced corrosion resistance can be associated to the increased proportion of Σ3 boundaries and reduced dislocation density, which together mitigate preferential corrosion paths. Overall, the study establishes that PWHT enhances the microstructural stability, mechanical uniformity, and corrosion resistance of HNS weldments, making it a promising approach for critical applications in corrosive environments.