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<p>Duplex stainless steel containing ferrite and austenite phases has been widely used in pipelines, pressure vessels, and heat exchangers because of its high strength and good corrosion resistance. However, when duplex stainless steel is fabricated by selective laser melting (SLM), the austenite fraction can decrease markedly. In this work, the effects of nitrogen on the microstructure and mechanical properties were investigated by changing nitrogen content in shielding gas from 0 to 100&#xa0;vol.%. The results show that, as the nitrogen content in the shielding gas increases, the nitrogen content in the samples and the austenite fraction first increase and then level off, due to the austenite-stabilizing effect of nitrogen and its limited solubility. The grain size shows a similar trend, decreasing first and then stabilizing, mainly because both increased cooling rate and grain boundary austenite pinning. Nitrogen atoms are located in the octahedral interstices of the austenite lattice and form an interstitial solid solution. The ferrite phase shows a <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\left\langle {00{1}} \right\rangle\)</EquationSource> <EquationSource Format="MATHML"><math> <mfenced close="〉" open="〈"> <mrow> <mn>001</mn> </mrow> </mfenced> </math></EquationSource> </InlineEquation> texture, while the austenite phase exhibits a much weaker texture. The reason is related to different formation mechanisms and the ferrite–austenite orientation relationship follows the N–W orientation relationship. No Cr2N precipitates are observed at ferrite grain boundaries or inside grains, which is attributed to rapid solidification. With increasing nitrogen content in the shielding gas, the tensile strength and elongation first increase and then decrease, due to the combined effects of increased austenite content, grain refinement, solid solution strengthening, and increased porosity defects. When the nitrogen content in the shielding gas is 12&#xa0;vol.%, the maximum tensile strength is 999.1 MPa and the elongation at break is 15.3%.</p>

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In situ nitrogen alloying of duplex stainless steel by selective laser melting: microstructure evolution and enhancement of mechanical properties

  • 期刊论文

  • 发表日期：

    2026年3月25日

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  • Hongliang Xiang,
  • Yongkang Xiao,
  • Feng Li,
  • Gang Mou,
  • Ye Huang

摘要

Duplex stainless steel containing ferrite and austenite phases has been widely used in pipelines, pressure vessels, and heat exchangers because of its high strength and good corrosion resistance. However, when duplex stainless steel is fabricated by selective laser melting (SLM), the austenite fraction can decrease markedly. In this work, the effects of nitrogen on the microstructure and mechanical properties were investigated by changing nitrogen content in shielding gas from 0 to 100 vol.%. The results show that, as the nitrogen content in the shielding gas increases, the nitrogen content in the samples and the austenite fraction first increase and then level off, due to the austenite-stabilizing effect of nitrogen and its limited solubility. The grain size shows a similar trend, decreasing first and then stabilizing, mainly because both increased cooling rate and grain boundary austenite pinning. Nitrogen atoms are located in the octahedral interstices of the austenite lattice and form an interstitial solid solution. The ferrite phase shows a \(\left\langle {00{1}} \right\rangle\) 001 texture, while the austenite phase exhibits a much weaker texture. The reason is related to different formation mechanisms and the ferrite–austenite orientation relationship follows the N–W orientation relationship. No Cr2N precipitates are observed at ferrite grain boundaries or inside grains, which is attributed to rapid solidification. With increasing nitrogen content in the shielding gas, the tensile strength and elongation first increase and then decrease, due to the combined effects of increased austenite content, grain refinement, solid solution strengthening, and increased porosity defects. When the nitrogen content in the shielding gas is 12 vol.%, the maximum tensile strength is 999.1 MPa and the elongation at break is 15.3%.