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<p>Maraging steels&#xa0;fabricated by laser powder bed fusion (L-PBF) are highly sensitive to oxide inclusions, which strongly affect their microstructural integrity and mechanical performance. Although prior studies have examined oxide formation in L-PBF steels, they have largely focused on process-induced variables, making it difficult to isolate the intrinsic role of oxygen chemistry. This study addresses this gap by investigating the influence of powder-inherent oxygen content on oxide evolution and properties. Most importantly, it provides the systematic isolation of powder oxygen effects—independent of processing parameters—and establishes oxygen concentration as a critical materials-centric quality metric for controlling inclusion evolution and fracture behavior in L-PBF maraging steels. Powders with varying oxygen levels (~ 180 ppm, ~ 310 ppm, and ~ 460 ppm) were employed to examine how oxidation affects microstructural integrity and performance. High-resolution microscopy analysis identified six distinct oxide types—including Al₂O₃, SiO₂, and complex Mn-, Cr-, and Zr-bearing inclusions—whose formation trends were supported by thermodynamic calculations using Thermo-Calc. As oxygen content increased, a transition was observed from fine, uniformly dispersed Al-rich oxides to coarser, spatially clustered Mn- and Si-rich inclusions. Moreover, nanoindentation testing revealed a systematic decrease in resistance to localized deformation, accompanied by pronounced pile-up and cracking around the indent sites—clear indicators of compromised surface mechanical quality. Complementary tensile and cryogenic impact tests also showed that while tensile strength exhibited only moderate reductions, toughness was highly sensitive to oxide morphology. Fractographic observations further confirmed a shift from ductile dimpled fracture in low-oxygen samples to brittle intergranular fracture in high-oxygen conditions.</p>

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Effect of powder oxygen content on inclusion morphology and mechanical behavior of maraging steels processed by laser powder bed fusion

  • 期刊论文

  • 发表日期：

    2025年10月16日

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  • Suleiman Ibrahim Mohammad,
  • Hamza Abu Owida,
  • Raman Kumar,
  • Nagappan Beemkumar,
  • Abinash Mahapatro,
  • Ashwin Jacob,
  • Ruby Pant

摘要

Maraging steels fabricated by laser powder bed fusion (L-PBF) are highly sensitive to oxide inclusions, which strongly affect their microstructural integrity and mechanical performance. Although prior studies have examined oxide formation in L-PBF steels, they have largely focused on process-induced variables, making it difficult to isolate the intrinsic role of oxygen chemistry. This study addresses this gap by investigating the influence of powder-inherent oxygen content on oxide evolution and properties. Most importantly, it provides the systematic isolation of powder oxygen effects—independent of processing parameters—and establishes oxygen concentration as a critical materials-centric quality metric for controlling inclusion evolution and fracture behavior in L-PBF maraging steels. Powders with varying oxygen levels (~ 180 ppm, ~ 310 ppm, and ~ 460 ppm) were employed to examine how oxidation affects microstructural integrity and performance. High-resolution microscopy analysis identified six distinct oxide types—including Al₂O₃, SiO₂, and complex Mn-, Cr-, and Zr-bearing inclusions—whose formation trends were supported by thermodynamic calculations using Thermo-Calc. As oxygen content increased, a transition was observed from fine, uniformly dispersed Al-rich oxides to coarser, spatially clustered Mn- and Si-rich inclusions. Moreover, nanoindentation testing revealed a systematic decrease in resistance to localized deformation, accompanied by pronounced pile-up and cracking around the indent sites—clear indicators of compromised surface mechanical quality. Complementary tensile and cryogenic impact tests also showed that while tensile strength exhibited only moderate reductions, toughness was highly sensitive to oxide morphology. Fractographic observations further confirmed a shift from ductile dimpled fracture in low-oxygen samples to brittle intergranular fracture in high-oxygen conditions.