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<p>The present work explores corrosion response of Selective Laser Melting (SLM) prepared NiTi shape memory alloys with an aim to study processing-induced defects and surface-specific microstructural features inherent to SLM, influence on alloy corrosion response. The study systematically investigated corrosion behavior within the defect-minimized region of established SLM printability maps by comparing representative low- and high-power/scan speed conditions (P-80: 80&#xa0;W, 330&#xa0;mm s⁻¹; P-200: 200&#xa0;W, 1080&#xa0;mm s⁻¹) and by varying hatch spacing (64&#xa0;μm and 80&#xa0;μm) under constant laser power and scan speed. Corrosion behavior analysis was carried out on four distinct surfaces following a 72-h immersion in Hank’s Balanced Salt Solution (HBSS): the internal and external surface of P-80 and P-200 specimens sectioned parallel to build direction (BD), and top and bottom surface of h-64 and h-80 specimens sectioned perpendicular to BD. Unlike prior studies that compared SLM NiTi against wrought material or varied parameters broadly, this work systematically isolates surface-specific defect populations within the defect-minimized region of an established printability map at matched volumetric energy density. The parallel to BD, P-80 specimens, showed the highest porosity of 5.4% and a corrosion current density of 140 nA/cm², with localized pits reaching up to 110&#xa0;μm in depth, initiating primarily at porosity defects thereby disrupting the passive film formation. In contrast, perpendicular to BD specimens, particularly h-80 with larger hatch spacings, showed enhanced corrosion resistance on a single-specimen basis, attributed to a more effective passive film formation. Surfaces with higher defect density developed effective thicker but defect-rich passive films with poor protective performance, whereas Ti-enriched, low-defect surfaces formed effective thinner yet compact and highly resistive films. These results indicate that within the defect-minimized region of the printability map, surface-specific defect populations and surface chemistry are the dominant factors governing corrosion response, rather than nominal process parameters. The findings imply that build-orientation selection and surface-specific post-processing—beyond bulk-density optimization—are required for corrosion-critical SLM NiTi components. Direct passive-film characterization, replicate testing, and Ni-ion-release quantification are identified as essential follow-on work.</p>

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Corrosion behavior of selective laser melted NiTi shape memory alloy

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月23日

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  • Anurag Srivastava,
  • Adnan Khan,
  • Vasanth C. Shunmugasamy,
  • Chaudhry Ali Usman,
  • Alaa Elwany,
  • Ibrahim Karaman,
  • Bilal Mansoor

摘要

The present work explores corrosion response of Selective Laser Melting (SLM) prepared NiTi shape memory alloys with an aim to study processing-induced defects and surface-specific microstructural features inherent to SLM, influence on alloy corrosion response. The study systematically investigated corrosion behavior within the defect-minimized region of established SLM printability maps by comparing representative low- and high-power/scan speed conditions (P-80: 80 W, 330 mm s⁻¹; P-200: 200 W, 1080 mm s⁻¹) and by varying hatch spacing (64 μm and 80 μm) under constant laser power and scan speed. Corrosion behavior analysis was carried out on four distinct surfaces following a 72-h immersion in Hank’s Balanced Salt Solution (HBSS): the internal and external surface of P-80 and P-200 specimens sectioned parallel to build direction (BD), and top and bottom surface of h-64 and h-80 specimens sectioned perpendicular to BD. Unlike prior studies that compared SLM NiTi against wrought material or varied parameters broadly, this work systematically isolates surface-specific defect populations within the defect-minimized region of an established printability map at matched volumetric energy density. The parallel to BD, P-80 specimens, showed the highest porosity of 5.4% and a corrosion current density of 140 nA/cm², with localized pits reaching up to 110 μm in depth, initiating primarily at porosity defects thereby disrupting the passive film formation. In contrast, perpendicular to BD specimens, particularly h-80 with larger hatch spacings, showed enhanced corrosion resistance on a single-specimen basis, attributed to a more effective passive film formation. Surfaces with higher defect density developed effective thicker but defect-rich passive films with poor protective performance, whereas Ti-enriched, low-defect surfaces formed effective thinner yet compact and highly resistive films. These results indicate that within the defect-minimized region of the printability map, surface-specific defect populations and surface chemistry are the dominant factors governing corrosion response, rather than nominal process parameters. The findings imply that build-orientation selection and surface-specific post-processing—beyond bulk-density optimization—are required for corrosion-critical SLM NiTi components. Direct passive-film characterization, replicate testing, and Ni-ion-release quantification are identified as essential follow-on work.