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<p>The present study investigates the mechanical properties, corrosion behavior, and high-temperature oxidation performance of functionally graded weld joints (FGWJs) and conventional dissimilar weld joints (Conv. DWJs) between P91 steel and AISI 304 stainless steel. The Conv. DWJ, fabricated without a filler metal, exhibited thermal expansion mismatch, a higher rate of corrosion, and non-protective oxide layer formation. To overcome these issues, FGWJs were fabricated using an activated TIG welding process (A-TIG) incorporating an Inconel 625 interlayer. The FGWJs demonstrated superior tensile strength (556 MPa) and ductility (34.8%), achieving a joint efficiency of 85.40%, compared to Conv. DWJ (479 MPa and 6.88%) with a joint efficiency of 73.57%. The improved corrosion resistance (0.7 mpy of FZII in FGWJ compared to 1.99 mpy of Conv. DWJ) was attributed to the modified austenitic phase of the fusion zones of FGWJ. Impact toughness was also improved (132 J), and dilatometry results confirmed the reduction in thermal expansion mismatch. High-temperature oxidation tests at 800&#xa0;°C revealed the formation of a dense internal Cr<sub>2</sub>O<sub>3</sub> layer and an external nickel-rich layer, which collectively suppressed the growth of the thermally grown oxide scale. The oxidation kinetics in FGWJs followed a parabolic rate law, further confirming their robust performance. The adopted fabrication strategy enhanced the thermal and mechanical stability of FGWJs, supporting their application in high-temperature environments such as chemical plants and power generation systems.</p>

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Influence of Inconel 625 Interlayer on the Development of Functionally Graded Weld Joints Between Ferritic/Martensitic Steel and Austenitic Stainless Steel via Activated Tungsten Inert Gas Welding

  • 期刊论文

  • 发表日期：

    2025年10月10日

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  • Rajat Malik,
  • Dheerendra Kumar Dwivedi

摘要

The present study investigates the mechanical properties, corrosion behavior, and high-temperature oxidation performance of functionally graded weld joints (FGWJs) and conventional dissimilar weld joints (Conv. DWJs) between P91 steel and AISI 304 stainless steel. The Conv. DWJ, fabricated without a filler metal, exhibited thermal expansion mismatch, a higher rate of corrosion, and non-protective oxide layer formation. To overcome these issues, FGWJs were fabricated using an activated TIG welding process (A-TIG) incorporating an Inconel 625 interlayer. The FGWJs demonstrated superior tensile strength (556 MPa) and ductility (34.8%), achieving a joint efficiency of 85.40%, compared to Conv. DWJ (479 MPa and 6.88%) with a joint efficiency of 73.57%. The improved corrosion resistance (0.7 mpy of FZII in FGWJ compared to 1.99 mpy of Conv. DWJ) was attributed to the modified austenitic phase of the fusion zones of FGWJ. Impact toughness was also improved (132 J), and dilatometry results confirmed the reduction in thermal expansion mismatch. High-temperature oxidation tests at 800 °C revealed the formation of a dense internal Cr2O3 layer and an external nickel-rich layer, which collectively suppressed the growth of the thermally grown oxide scale. The oxidation kinetics in FGWJs followed a parabolic rate law, further confirming their robust performance. The adopted fabrication strategy enhanced the thermal and mechanical stability of FGWJs, supporting their application in high-temperature environments such as chemical plants and power generation systems.