Laser Ultrasound Detects Metal 3D Printing Defects

Researchers have developed a new laser ultrasound technique capable of performing on-demand characterization of melt tracks and detecting the formation of defects in a popular metal 3D printing process.

The researchers propose a diagnostic using surface acoustic waves (SAW), generated by laser ultrasound, that can reveal tiny surface and sub-surface defects in laser powder bed fusion (LPBF) metal 3D printing. The system can effectively and accurately evaluate laser melt lines — the tracks where the laser liquefies metal powder in LPBF printing — by scattering acoustic energy from melt lines, voids, and surface features that can be quickly detected. The team validated the findings using optical microscopy and X-ray computed tomography (CT).

The research demonstrates the potential for an all-optical ultrasound system capable of rapid, on-demand in situ characterization of LPBF processes and powders. The demonstrated laser-based ultrasound surface acoustic wave system showed excellent sensitivity to surface and near-surface features, including breaks in the LPBF melt line, metal surface splatter, and subsurface air voids.

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