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<p>This study investigates the effect of shielding gas composition on laser self-fusion welded joints of N50 high-nitrogen austenitic stainless steel, focusing on microstructure, mechanical properties, and corrosion resistance. Experiments utilized pure Ar (100% Ar), a mixture (50% Ar + 50% N₂), and pure N₂ (100% N₂) as shielding gases. Results show that all welds exhibit similar austenite-dominated microstructures with trace of ferrite content; however, δ-ferrite decreases significantly with increasing nitrogen partial pressure, reaching the lowest level under 100% N₂ shielding. Tensile strength remains consistent across gases at ~ 670&#xa0;MPa (85% of base metal strength), but elongation peaks at 50.7% (95.5% of base metal elongation) for 100% N₂-protected welds, indicating superior ductility. Fractography confirms ductile fracture via microvoid coalescence. Corrosion resistance in 3.5 wt.% NaCl solution ranks as 100% N₂ &gt; 50% N₂ + 50% Ar &gt; 100% Ar based on electrochemical tests. These findings demonstrate that nitrogen-rich shielding gases enhance weld ductility and corrosion resistance without compromising tensile strength, offering improved alternatives to traditional argon shielding.</p>

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Effect of Shielding Gas Composition on Microstructure and Mechanical Properties of N50 Stainless Steel Laser Welds

  • 期刊论文

  • 发表日期：

    2026年6月27日

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  • Ruize Xu,
  • Yushan Wang,
  • Yichen Li,
  • Jiaming Li,
  • Guanlin Zhao,
  • Yong Zou

摘要

This study investigates the effect of shielding gas composition on laser self-fusion welded joints of N50 high-nitrogen austenitic stainless steel, focusing on microstructure, mechanical properties, and corrosion resistance. Experiments utilized pure Ar (100% Ar), a mixture (50% Ar + 50% N₂), and pure N₂ (100% N₂) as shielding gases. Results show that all welds exhibit similar austenite-dominated microstructures with trace of ferrite content; however, δ-ferrite decreases significantly with increasing nitrogen partial pressure, reaching the lowest level under 100% N₂ shielding. Tensile strength remains consistent across gases at ~ 670 MPa (85% of base metal strength), but elongation peaks at 50.7% (95.5% of base metal elongation) for 100% N₂-protected welds, indicating superior ductility. Fractography confirms ductile fracture via microvoid coalescence. Corrosion resistance in 3.5 wt.% NaCl solution ranks as 100% N₂ > 50% N₂ + 50% Ar > 100% Ar based on electrochemical tests. These findings demonstrate that nitrogen-rich shielding gases enhance weld ductility and corrosion resistance without compromising tensile strength, offering improved alternatives to traditional argon shielding.