Mesoscopic Computational Fluid Dynamics Modelling for the Laser-Melting Deposition of AISI 304 Stainless Steel Single Tracks with Experimental Correlation: A Novel Study

Abstract

For laser-melting deposition (LMD), a computational fluid dynamics (CFD) model was developed using the volume of fluid and discrete element modeling techniques. A method was developed to track the flow behavior, flow pattern, and driving forces of liquid flow. The developed model was compared with experimental results in the case of AISI 304 stainless steel single-track depositions on AISI 304 stainless steel substrate. A close correlation was found between experiments and modeling, with a deviation of 1–3%. It was found that the LMD involves the simultaneous addition of powder particles that absorb a significant amount of laser energy to transform their phase from solid to liquid, resulting in conduction-mode melt flow. The bubbles within the melt pool float at a specific velocity and escape from the melt pool throughout the deposition process. The pores are generated if the solid front hits the bubble before escaping the melt pool. Based on the simulations, it was discovered that the deposited layer’s counters took the longest time to solidify compared to the overall deposition. The bubbles strived to leave through the contours in an excess quantity, but became stuck during solidification, resulting in a large degree of porosity near the contours. The stream traces showed that the melt flow adopted a clockwise vortex in front of the laser beam and an anti-clockwise vortex behind the laser beam. The difference in the surface tension between the two ends of the melt pool induces “thermocapillary or Benard–Marangoni convection” force, which is insignificant compared to the selective laser melting process. After layer deposition, the melt region, mushy zone, and solidified region were identified. When the laser beam irradiates the substrate and powder particles are added simultaneously, the melt adopts a backwards flow due to the recoil pressure and thermocapillary or Benard–Marangoni convection effect, resulting in a negative mass flow rate. This study provides an in-depth understanding of melt pool dynamics and flow pattern in the case of LMD additive manufacturing technique.

Full-Field Mapping and Flow Quantification of Melt Pool Dynamics in Laser Powder Bed Fusion of SS316L

“…When the laser moves to irradiate the powder particles, a temperature/density gradient is created, leading to the difference in surface tension of both ends (Marangoni), as shown in Figure 9 a. Due to the Marangoni force, the flow is pulled backwards [ 44 , 60 , 61 , 62 ]. As the laser is melting the particles, it also pushes the melt pool downwards.…”

“…It has a medium chromium content as well as a high nickel concentration, which leads to good weldability and is indeed a significant advantage of SS316L in LPBF. This advantage is due to the low carbon and medium molybdenum concentration, which makes it resistant to hot and cold cracking [ 44 , 45 , 46 , 47 ].…”

Laser Melting Deposition Additive Manufacturing of Ti6Al4V Biomedical Alloy: Mesoscopic In-Situ Flow Field Mapping via Computational Fluid Dynamics and Analytical Modelling with Empirical Testing

“…The powder particles use a considerable fraction of the laser beam energy to change their phase from solid to liquid. In turn, it reduces the net amount of laser energy arriving at the substrate, resulting in only conduction-mode melt flow [52,72]. Figure 4a-d exhibits the section view of the LMD-ed layer, and CR melt-pool can be observed.…”

3D Multi-Track and Multi-Layer Epitaxy Grain Growth Simulations of Selective Laser Melting

“…Furthermore, the mechanical properties of even defect-free components are a function of their microstructural properties [ 8 ]. Rehman et al developed a mechanism for detecting the flow behavior within the whole melt pool [ 9 , 10 , 11 ] that can predict melt flow inside the melting pool. However, developing a thorough understanding of the microstructural evolution of SLM components is essential in producing high-quality defect-free parts with the required mechanical properties and performance.…”