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<p>This study addresses challenges in post-weld heat treatment (PWHT) performance of 9Cr-1Mo-V/304L steel dissimilar joints fabricated using tungsten inert gas (TIG) welding for next-generation power plants. The primary objective is to investigate and compare the influence of TIG welding techniques on PWHT performance of 9Cr-1Mo-V/304L steel dissimilar joints, specifically examining carbon diffusion, microstructural features, mechanical performance, and fracture behavior. The joints were fabricated using a novel technique of activated flux TIG (A-TIG) welding with AlCoFeCrNi<sub>2.1</sub> eutectic high-entropy alloy (EHEA) intermediate layer and conventional multiple-pass TIG (MP-TIG) welding with Inconel-based ErNiCr-3 filler, followed by PWHT of tempering at 760&#xa0;°C for 2&#xa0;hours. Results showed that the MP-TIG joints had inferior tensile strength of 575&#xa0;MPa, ductility of 21&#xa0;pct, and weld metal (WM) hardness of 190 HV<sub>0.5</sub> due to coarser, interconnected secondary precipitates in dendritic, entirely austenite (<i>γ</i>) WM microstructure, leading to premature failure with mixed fracture behavior in WM. However, they exhibited good WM toughness of 90&#xa0;J due to formation of new, finer secondary precipitates in WM after PWHT. A-TIG joints revealed superior tensile strength of 635&#xa0;MPa, ductility of 29.5&#xa0;pct, WM hardness of 358 HV<sub>0.5</sub>, and toughness of 102&#xa0;J due to evolution of the duplex tempered-martensite (<i>α</i>′<sub>T</sub>) and retained austenite (<i>γ</i><sub>R</sub>) microstructure with evenly distributed finer secondary precipitates in WM. This resulted in 10.43, 40.47, 88.42, and 13.34&#xa0;pct improvements in tensile strength, ductility, WM hardness, and toughness compared to MP-TIG joints. A-TIG joints exhibited less carbon diffusion during PWHT, resulting in a 16.19&#xa0;pct reduction in peak hardness near the weld metal interface (WMI) on 9Cr-1Mo-V steel side, due to lower net energy input, high-entropy effect, and functionally graded structure at WMI. However, PWHT led to premature mixed-mode tensile failure in intercritical heat-affected zone due to localized tensile deformation and necking in this softened region. This research provides new insights into suitability of EHEA intermediate layers for enhancing PWHT performance of dissimilar joints of creep-strength-enhanced martensitic steel and austenitic stainless steel for next-generation power plant applications.</p>

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Unveiling the Influence of A-TIG Welding with AlCoFeCrNi2.1 EHEA Intermediate Layer on PWHT Performance of 9Cr-1Mo-V/304L Steel Dissimilar Joints for Next-Generation Power Plants

  • 期刊论文

  • 发表日期：

    2025年11月6日

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  • Tushar Sonar,
  • Mikhail Ivanov,
  • Igor Shcherbakov,
  • Artem Okulov,
  • Nataliya Shaburova,
  • Evgeny Trofimov,
  • Aleksander Tingaev,
  • Sergey Samoilov,
  • Emiliya Khasanova,
  • Anmar Alruhaimi

摘要

This study addresses challenges in post-weld heat treatment (PWHT) performance of 9Cr-1Mo-V/304L steel dissimilar joints fabricated using tungsten inert gas (TIG) welding for next-generation power plants. The primary objective is to investigate and compare the influence of TIG welding techniques on PWHT performance of 9Cr-1Mo-V/304L steel dissimilar joints, specifically examining carbon diffusion, microstructural features, mechanical performance, and fracture behavior. The joints were fabricated using a novel technique of activated flux TIG (A-TIG) welding with AlCoFeCrNi2.1 eutectic high-entropy alloy (EHEA) intermediate layer and conventional multiple-pass TIG (MP-TIG) welding with Inconel-based ErNiCr-3 filler, followed by PWHT of tempering at 760 °C for 2 hours. Results showed that the MP-TIG joints had inferior tensile strength of 575 MPa, ductility of 21 pct, and weld metal (WM) hardness of 190 HV0.5 due to coarser, interconnected secondary precipitates in dendritic, entirely austenite (γ) WM microstructure, leading to premature failure with mixed fracture behavior in WM. However, they exhibited good WM toughness of 90 J due to formation of new, finer secondary precipitates in WM after PWHT. A-TIG joints revealed superior tensile strength of 635 MPa, ductility of 29.5 pct, WM hardness of 358 HV0.5, and toughness of 102 J due to evolution of the duplex tempered-martensite (α′T) and retained austenite (γR) microstructure with evenly distributed finer secondary precipitates in WM. This resulted in 10.43, 40.47, 88.42, and 13.34 pct improvements in tensile strength, ductility, WM hardness, and toughness compared to MP-TIG joints. A-TIG joints exhibited less carbon diffusion during PWHT, resulting in a 16.19 pct reduction in peak hardness near the weld metal interface (WMI) on 9Cr-1Mo-V steel side, due to lower net energy input, high-entropy effect, and functionally graded structure at WMI. However, PWHT led to premature mixed-mode tensile failure in intercritical heat-affected zone due to localized tensile deformation and necking in this softened region. This research provides new insights into suitability of EHEA intermediate layers for enhancing PWHT performance of dissimilar joints of creep-strength-enhanced martensitic steel and austenitic stainless steel for next-generation power plant applications.