Quantification of Interdependent Dynamics during Laser Additive Manufacturing Using X-Ray Imaging Informed...

Area of Science:

• Materials Science
• Manufacturing Engineering
• Additive Manufacturing

Background:

• Laser powder bed fusion (LPBF) is crucial for producing high-value metallic components.
• The widespread adoption of LPBF for safety-critical applications is hindered by process-induced imperfections.
• The relationship between LPBF processing parameters and defect formation is not fully understood.

Purpose of the Study:

• To quantify the evolution of porosity and humps during LPBF.
• To elucidate the mechanisms driving the formation of pores and humps.
• To provide insights for enhancing the reliability of LPBF processes.

Main Methods:

• Utilized X-ray and electron imaging for defect observation.
• Employed high-fidelity multiphase process simulation.
• Quantified pore evolution kinetics, size distribution, waviness, surface roughness, and melt volume.

Main Results:

• Identified keyhole collapse, pore coalescence, and entrapment as mechanisms for irregular pore formation.
• Revealed that pore formation is driven by high temperatures and metal vapor concentration within the keyhole.
• Demonstrated that Kelvin-Helmholtz instability at the melt track surface causes hump formation due to vapor plume and molten pool interaction.

Conclusions:

• The study clarifies the formation mechanisms of porosity and humps in LPBF.
• Understanding these mechanisms is critical for controlling imperfections.
• The findings offer a basis for improving process reliability in additive manufacturing.