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<p>This research explores the influence of welding parameters on dissimilar joints between low-alloy steels (T12, T22, T91) and TP347H austenitic stainless steel produced by auto TIG welding with Inconel filler. The work emphasizes the challenges of carbon migration on the T91 fusion line and sensitization on the TP347H heat-affected zone (HAZ). Microhardness testing, tensile and bend evaluations, ASTM A262 practices A and E, and SEM–EDS elemental mapping were employed to correlate mechanical performance with intergranular corrosion susceptibility. Results reveal that high heat input (≈1.124&#xa0;kJ/mm) promotes extensive carbon migration at the T91 fusion line, the formation of brittle martensitic zones with hardness up to 400 VHN, and ditch microstructures on TP347H HAZ, leading to cracking during bend tests. Conversely, optimized low heat input (≈0.606–0.792&#xa0;kJ/mm) restricted carbon diffusion, reduced HAZ hardness to ~ 295 VHN, and improved tensile strength (up to 680&#xa0;MPa) with satisfactory bend performance. Dual microstructures and orange-peel morphology confirmed lower susceptibility to sensitization and intergranular corrosion under optimized welding conditions. SEM–EDS chromium line mapping validated these findings, showing limited Cr depletion and reduced carbide precipitation. Overall, optimized auto TIG welding with reduced heat input significantly enhances the mechanical integrity and corrosion resistance of dissimilar welds, providing a reliable approach for advanced high-temperature boiler applications.</p>

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Heat input–microstructure–corrosion relationship in auto TIG–welded joints between low-alloy steels (T12, T22, and T91) and austenitic stainless steel (TP347H)

  • 期刊论文

  • 发表日期：

    2025年11月10日

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  • Pradip Gajjar,
  • Hiren R. Prajapati,
  • Alpesh M. Patel,
  • Digant S. Mehta,
  • Nilesh M. Bhangale,
  • Bhargav B. Patel,
  • Vipul K. Patel

摘要

This research explores the influence of welding parameters on dissimilar joints between low-alloy steels (T12, T22, T91) and TP347H austenitic stainless steel produced by auto TIG welding with Inconel filler. The work emphasizes the challenges of carbon migration on the T91 fusion line and sensitization on the TP347H heat-affected zone (HAZ). Microhardness testing, tensile and bend evaluations, ASTM A262 practices A and E, and SEM–EDS elemental mapping were employed to correlate mechanical performance with intergranular corrosion susceptibility. Results reveal that high heat input (≈1.124 kJ/mm) promotes extensive carbon migration at the T91 fusion line, the formation of brittle martensitic zones with hardness up to 400 VHN, and ditch microstructures on TP347H HAZ, leading to cracking during bend tests. Conversely, optimized low heat input (≈0.606–0.792 kJ/mm) restricted carbon diffusion, reduced HAZ hardness to ~ 295 VHN, and improved tensile strength (up to 680 MPa) with satisfactory bend performance. Dual microstructures and orange-peel morphology confirmed lower susceptibility to sensitization and intergranular corrosion under optimized welding conditions. SEM–EDS chromium line mapping validated these findings, showing limited Cr depletion and reduced carbide precipitation. Overall, optimized auto TIG welding with reduced heat input significantly enhances the mechanical integrity and corrosion resistance of dissimilar welds, providing a reliable approach for advanced high-temperature boiler applications.