Hole Morphology and Keyhole Evolution during Single Pulse Laser Drilling on Polyether-Ether-Ketone (PEEK)

Area of Science:

• Materials Science
• Laser Processing
• Polymer Engineering

Background:

• Polyether-ether-ketone (PEEK) possesses excellent mechanical, chemical, thermal, and biocompatible properties, making it suitable for aerospace, electronics, and biomedical fields.
• Accurate laser drilling of PEEK is crucial for its advanced applications, necessitating a deep understanding of the drilling process and material interactions.

Purpose of the Study:

• To investigate the single-pulse laser drilling process on PEEK, focusing on hole morphology and keyhole evolution.
• To develop and utilize a novel method for rapid in-situ observation and measurement of laser-drilled polymer holes.
• To elucidate the material removal mechanisms and their dependence on laser parameters.

Main Methods:

• Performed extensive single-pulse laser drilling experiments on PEEK.
• Utilized optical microscopy, charge-coupled device (CCD) imaging, and high-speed cameras for characterization and in-situ observation.
• Analyzed hole morphology, keyhole dynamics, ejection, and vaporization behaviors.
• Calculated dimensionless laser power density and compared experimental drilling depth with energy balance predictions.

Main Results:

• Achieved a maximum drilling depth of 7.06 mm and an aspect ratio of 23.
• Identified three keyhole evolution stages: rapid increment (0–2 ms), slow increment (2–4 ms), and stable (>4 ms).
• Determined that material removal is dominated by ejection (>60% depth increment in rapid stage) and vaporization (~80% depth increment in slow stage).

Conclusions:

• The laser-PEEK interaction is primarily governed by a photothermal effect.
• Understanding material removal mechanisms (ejection and vaporization) is critical for optimizing single-pulse laser drilling of PEEK.
• The findings provide a processing window for PEEK laser drilling and guidance for manufacturing other polymers.