Understanding Melt Pool Behavior of 316L Stainless Steel in Laser Powder Bed Fusion Additive Manufacturing.

Area of Science:

• Materials Science
• Additive Manufacturing
• Computational Modeling

Background:

• Laser powder bed fusion (LPBF) quality depends on laser-matter interaction and melt pool dynamics.
• Understanding melt pool behavior is crucial for optimizing fabrication processes and material properties.

Purpose of the Study:

• To experimentally investigate melt pool characteristics and surface topography in 316L stainless steel during LPBF.
• To develop and validate a high-fidelity computational model for predicting melt pool dynamics and surface features.
• To elucidate the mechanisms behind defective morphologies, such as swell-undercut.

Main Methods:

• Single-track laser scanning experiments on bare plate and powder bed for 316L stainless steel.
• Development of a computational model incorporating fluid dynamics, heat transfer, vaporization, and solidification.
• Validation of the model against experimental melt pool dimensions and morphology.
• Multiple-track simulations to replicate surface features and assess process optimization potential.

Main Results:

• The powder layer significantly increases melt pool instability and surface irregularities compared to a bare plate.
• The computational model accurately predicts melt pool dimensions, morphology, and transition between conduction and keyholing modes.
• The model successfully explains the formation of swell-undercut defects, attributing them to recoil pressure and liquid refilling dynamics.
• Simulations demonstrate the model's capability to replicate surface features under various process conditions.

Conclusions:

• Powder layer presence introduces instabilities that degrade surface quality in LPBF of 316L stainless steel.
• The validated computational model provides a powerful tool for understanding and predicting melt pool behavior and defect formation.
• This research offers insights into optimizing LPBF process parameters for improved fabrication quality and defect reduction.