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<p>Laser powder bed fusion (LPBF) is widely used to create intricate parts. One of the challenges in using the LPBF technique is to improve the density of the metal components created, especially regarding processing parameters and volumetric energy density (<i>V</i><sub>ED</sub>). This research investigated the impact of 25 different <i>V</i><sub>EDs</sub>(ranging from 31.47 to 92.86&#xa0;J/mm<sup>3</sup>) on creating LPBF-printed 321 stainless steel specimens (SS321). However, the study intends to minimize porosity; achieve optimal microstructure, surface quality, residual stress, and hardness; and identify the best parameters for SS321. Moreover, the experimental findings indicated that the relative density of the specimen reached 99.21%, with a surface roughness of around 9.24&#xa0;µm at an energy density of 73.86&#xa0;J/mm<sup>3</sup>. Conversely, higher roughness was observed (18.4&#xa0;µm) at a lower <i>V</i><sub>ED</sub> value of 37.88&#xa0;J/mm<sup>3</sup>. This occurrence can be attributed to the presence of partially melted powder particles and minor cracks caused by incomplete melting processes. Additionally, the microstructures of the specimens in their as-built condition showed columnar and cellular patterns observed at various energy density levels. However, the grains located away from the edge of the molten pool exhibited a cellular structure, which resulted from the gradual reduction in temperature gradient and solidification rate. Samples made with the maximum laser power of 260 W and a scanning speed between 900 and 1100&#xa0;mm/s, along with a <i>V</i><sub>ED</sub> range of 65.66 to 73.86&#xa0;J/mm<sup>3</sup>, demonstrated the highest densification and hardness (221.3 to 247.2 HV) and the most refined microstructure. Furthermore, this study has the potential to offer direction for enhancing <i>V</i><sub>ED</sub> to achieve a more uniform microstructure, increased density, and higher production efficiency for LPBF manufacturing.&#xa0;&#xa0;</p> Graphical Abstract <p></p>

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Study on the influence of volumetric energy density on densification, surface integrity, and microstructural properties of laser powder bed fusion fabricated 321 stainless steel parts

  • 期刊论文

  • 发表日期：

    2025年5月5日

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  • Elango Venkatachalam,
  • Devendiran Sundararajan

摘要

Laser powder bed fusion (LPBF) is widely used to create intricate parts. One of the challenges in using the LPBF technique is to improve the density of the metal components created, especially regarding processing parameters and volumetric energy density (VED). This research investigated the impact of 25 different VEDs(ranging from 31.47 to 92.86 J/mm3) on creating LPBF-printed 321 stainless steel specimens (SS321). However, the study intends to minimize porosity; achieve optimal microstructure, surface quality, residual stress, and hardness; and identify the best parameters for SS321. Moreover, the experimental findings indicated that the relative density of the specimen reached 99.21%, with a surface roughness of around 9.24 µm at an energy density of 73.86 J/mm3. Conversely, higher roughness was observed (18.4 µm) at a lower VED value of 37.88 J/mm3. This occurrence can be attributed to the presence of partially melted powder particles and minor cracks caused by incomplete melting processes. Additionally, the microstructures of the specimens in their as-built condition showed columnar and cellular patterns observed at various energy density levels. However, the grains located away from the edge of the molten pool exhibited a cellular structure, which resulted from the gradual reduction in temperature gradient and solidification rate. Samples made with the maximum laser power of 260 W and a scanning speed between 900 and 1100 mm/s, along with a VED range of 65.66 to 73.86 J/mm3, demonstrated the highest densification and hardness (221.3 to 247.2 HV) and the most refined microstructure. Furthermore, this study has the potential to offer direction for enhancing VED to achieve a more uniform microstructure, increased density, and higher production efficiency for LPBF manufacturing.  

Graphical Abstract