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<p>In the present study, block structures of austenitic grade SS 316LN steel were built using the laser-directed energy deposition (LDED) technique. Various process parameters were optimized to produce defect and crack-free SS 316LN blocks. Microscopic analysis and synchrotron-based x-ray micro-computed tomography (SR-μCT) revealed that the structure built at a laser power of 950 W exhibited no porosity or defect formation, in contrast to structures built at lower (800 W) and higher (1200 W) laser powers. Microstructural characterization using electron microscopy showed a significant morphological transition from cellular to equiaxed dendritic structures in different directions relative to the scan path. Largely, columnar grains are found to be aligned along the build direction with a &lt; 001 &gt; orientation. The texture analysis indicated a strong fiber texture with preferential orientation along the build direction, specifically &lt; 001 &gt; or &lt; 101 &gt; . Additionally, synchrotron-based x-ray diffraction (XRD) confirmed the dominance of the austenitic (γ-FCC) phase, with a minor presence of ferritic (δ-BCC) phase, which was further validated by differential scanning calorimetry and phase field simulations. The tensile properties of the defect-free samples were found to surpass those of conventionally wrought SS 316LN in all orientations relative to the scan direction. However, samples containing porosity exhibited a reduction in total elongation to approximately 10% along the build direction. Temperature-dependent elastic properties are also evaluated to assess high-temperature mechanical stability. Electrochemical test results in a 3.5% NaCl solution demonstrated excellent passivation behavior and enhanced pitting resistance of the additively manufactured SS 316LN steel.</p>

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Studies on Microstructural Stability, Thermomechanical Properties, and Electrochemical Behavior of LDED-built SS 316LN Steel

  • 期刊论文

  • 发表日期：

    2026年3月16日

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  • G. K. Mishra,
  • A. K. Rai,
  • Pooja Gupta,
  • V. Karthik,
  • C. P. Paul

摘要

In the present study, block structures of austenitic grade SS 316LN steel were built using the laser-directed energy deposition (LDED) technique. Various process parameters were optimized to produce defect and crack-free SS 316LN blocks. Microscopic analysis and synchrotron-based x-ray micro-computed tomography (SR-μCT) revealed that the structure built at a laser power of 950 W exhibited no porosity or defect formation, in contrast to structures built at lower (800 W) and higher (1200 W) laser powers. Microstructural characterization using electron microscopy showed a significant morphological transition from cellular to equiaxed dendritic structures in different directions relative to the scan path. Largely, columnar grains are found to be aligned along the build direction with a < 001 > orientation. The texture analysis indicated a strong fiber texture with preferential orientation along the build direction, specifically < 001 > or < 101 > . Additionally, synchrotron-based x-ray diffraction (XRD) confirmed the dominance of the austenitic (γ-FCC) phase, with a minor presence of ferritic (δ-BCC) phase, which was further validated by differential scanning calorimetry and phase field simulations. The tensile properties of the defect-free samples were found to surpass those of conventionally wrought SS 316LN in all orientations relative to the scan direction. However, samples containing porosity exhibited a reduction in total elongation to approximately 10% along the build direction. Temperature-dependent elastic properties are also evaluated to assess high-temperature mechanical stability. Electrochemical test results in a 3.5% NaCl solution demonstrated excellent passivation behavior and enhanced pitting resistance of the additively manufactured SS 316LN steel.