In situ x-ray imaging to understand subsurface behavior during continuous wave laser drilling

A limited understanding regarding the underlying dynamics and mechanisms of material removal during continuous wave laser drilling has presented significant challenges in achieving precision and process control. To address this, we employed high-fidelity, in situ synchrotron x-ray imaging to reveal...

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Bibliographic Details
Published in:Applied physics letters 2024-08, Vol.125 (6)
Main Authors: Gorgannejad, Sanam, Martin, Aiden A., Chen, Brian, Nicolino, Jenny W., Strantza, Maria, Guss, Gabriel M., Forien, Jean-Baptiste, Thampy, Vivek, Liu, Sen, Quan, Peiyu, Tassone, Christopher J., Calta, Nicholas P.
Format: Article
Language:English
Subjects:
Aspect ratio
Continuous wave lasers
Drilling
Ejection
Frequency modulation
Image processing
Laser drilling
Lasers
Liquid metals
Liquid solid interfaces
Liquid-vapor interface
Melt pools
Modulation
Physics
Process controls
Substrates
Synchrotron radiation
Welding
X ray imagery
X-ray imaging
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Summary:A limited understanding regarding the underlying dynamics and mechanisms of material removal during continuous wave laser drilling has presented significant challenges in achieving precision and process control. To address this, we employed high-fidelity, in situ synchrotron x-ray imaging to reveal previously unknown material behaviors during continuous wave laser drilling with power modulation. Our findings highlight that high-aspect ratio drill holes are achieved when the laser modulation frequency falls within the range of 8–12 kHz, provided that the laser average power and modulation amplitude levels meet the specified limits. Under these conditions, we identified a material removal mechanism driven by incremental accumulation of recoil pressure that gradually pushes material upward from deep within the substrate to the surface. This mechanism manifested as a low-frequency fluctuation in the vapor depression depth, resulting in periodic instances of material ejection. Furthermore, our study underscores that rapid expansion of the melt pool and the widening of the drill hole opening can impede effective material removal by redirecting energy from material ejection to increasing the melt pool size. This investigation contributes essential insights into the subsurface dynamics involved in the drilling of high-aspect ratio holes, furthering our fundamental understanding of this intricate process.
ISSN:0003-6951
1077-3118
DOI:10.1063/5.0207380