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<p>The corrosion reliability of welded austenitic stainless steels remains a critical challenge in chloride containing service environments, particularly when post-weld thermal exposure alters the stability of δ-ferrite and promotes sensitization phenomena within the weld region. Although post-weld heat treatment (PWHT) is frequently applied to improve structural integrity, its effect on the balance between mechanical performance and localized corrosion resistance in GTAW-welded AISI 316 stainless steel joints is still insufficiently understood. In the present work, AISI 316 plates welded using ER316L filler metal were subjected to PWHT at 850&#xa0;°C and 1100&#xa0;°C for 1&#xa0;h followed by water quenching in order to clarify the relationship between phase evolution, microstructural homogenization, and corrosion behavior. Microstructural characterization was carried out using optical microscopy, EBSD, EDS, and XRD analyses, while tensile testing, microhardness measurements, and potentiodynamic polarization tests in 3.5 wt% NaCl solution were performed to evaluate the mechanical and electrochemical responses of the welded joints. The as-welded condition exhibited a heterogeneous γ-austenitic weld structure containing approximately 5.8% δ-ferrite and showed the best overall corrosion resistance, with the lowest corrosion current density (0.15 µA/cm²) and corrosion rate (1.73&#xa0;μm/y). Heat treatment at 850&#xa0;°C promoted chromium carbide precipitation and severe sensitization, resulting in marked degradation of corrosion resistance and surface stability. Conversely, treatment at 1100&#xa0;°C reduced the δ-ferrite fraction to nearly 2.2%, enhanced chemical homogenization, and improved ductility, with elongation increasing to 64.23%. Despite the formation of deeper isolated pits, the electrochemical response of this condition remained significantly more stable than that of the 850&#xa0;°C-treated joint. The results demonstrate that PWHT temperature critically controls the competition between sensitization and microstructural homogenization in GTAW AISI 316/ER316L welds, thereby governing the resulting mechanical performance and corrosion behavior.</p>

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Effect of PWHT on microstructural evolution, mechanical properties, and corrosion behavior of GTAW-welded AISI 316 stainless steel

  • 期刊论文

  • 发表日期：

    2026年6月27日

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  • Ayman Khaled,
  • Mokhtar Djendel,
  • Ahmed Kellai,
  • Antonello Astarita,
  • Walid Jomaa

摘要

The corrosion reliability of welded austenitic stainless steels remains a critical challenge in chloride containing service environments, particularly when post-weld thermal exposure alters the stability of δ-ferrite and promotes sensitization phenomena within the weld region. Although post-weld heat treatment (PWHT) is frequently applied to improve structural integrity, its effect on the balance between mechanical performance and localized corrosion resistance in GTAW-welded AISI 316 stainless steel joints is still insufficiently understood. In the present work, AISI 316 plates welded using ER316L filler metal were subjected to PWHT at 850 °C and 1100 °C for 1 h followed by water quenching in order to clarify the relationship between phase evolution, microstructural homogenization, and corrosion behavior. Microstructural characterization was carried out using optical microscopy, EBSD, EDS, and XRD analyses, while tensile testing, microhardness measurements, and potentiodynamic polarization tests in 3.5 wt% NaCl solution were performed to evaluate the mechanical and electrochemical responses of the welded joints. The as-welded condition exhibited a heterogeneous γ-austenitic weld structure containing approximately 5.8% δ-ferrite and showed the best overall corrosion resistance, with the lowest corrosion current density (0.15 µA/cm²) and corrosion rate (1.73 μm/y). Heat treatment at 850 °C promoted chromium carbide precipitation and severe sensitization, resulting in marked degradation of corrosion resistance and surface stability. Conversely, treatment at 1100 °C reduced the δ-ferrite fraction to nearly 2.2%, enhanced chemical homogenization, and improved ductility, with elongation increasing to 64.23%. Despite the formation of deeper isolated pits, the electrochemical response of this condition remained significantly more stable than that of the 850 °C-treated joint. The results demonstrate that PWHT temperature critically controls the competition between sensitization and microstructural homogenization in GTAW AISI 316/ER316L welds, thereby governing the resulting mechanical performance and corrosion behavior.