Geometry and Surface Feature Evaluation in E-PBF Process Using In-Operando Electron Emission Signal.

Area of Science:

• Materials Science
• Additive Manufacturing
• Process Monitoring

Background:

• Electron beam powder bed fusion (E-PBF) necessitates robust in situ process monitoring.
• Electron emission signals are a promising, yet underexplored, method for real-time feedback.
• Previous research often relied on post-processing or separate scans, questioning in-melt signal utility.

Purpose of the Study:

• To evaluate the in-operando electron emission signal for reconstructing geometric and topographical features during E-PBF.
• To assess the signal's capability for real-time monitoring of complex part features.
• To compare in-operando signal reconstruction with established ground truth methods.

Main Methods:

• Recorded in-operando electron emission signals during spot-melting of Ti-6Al-4V spur gears.
• Utilized optical microscopy and profilometry as ground truth for geometric and topographical data.
• Applied a melt-pool dilation correction to account for thermal expansion effects.

Main Results:

• Achieved agreement deviation below 2.2% for geometric features after correction, comparable to post-melt imaging.
• Demonstrated strong correlation (Pearson 0.67-0.87) between electron emission signals and surface topography height profiles.
• Confirmed that the signal captures both geometric boundaries and meaningful surface variations.

Conclusions:

• The in-operando electron emission signal is highly effective for in situ geometric and topographical assessment in E-PBF.
• This technique offers significant potential for integration into closed-loop additive manufacturing quality control systems.
• Supports the use of real-time electron emission data for monitoring complex part fabrication.