Unveiling laser percussion drilling in metals with ultrashort pulses: insights from high-speed synchrotron x-ray imaging on microhole formation and side channel phenomena

Abstract

The comprehension of microhole formation during percussion drilling of metals using ultrashort laser pulses is still limited. The shape of a microhole can be impacted by factors like heat accumulation, the emergence of side channels, bending, and bulging. Understanding these defects is challenging due to constraints in conventional diagnostics. To address this issue, high-speed synchrotron x-ray imaging was employed to capture the spatial and temporal evolution of the microhole shape during laser percussion drilling of stainless steel. The recorded images reveal that heat accumulation leads to the creation of a melt film on the microhole walls, exhibiting dynamic fluctuations throughout the drilling process. Furthermore, a transversal widening or bulging of the microhole can be seen later in the process. Additionally, the emergence of side channels was observed in the region of maximum drilling depth, where the overall fluence on the microhole walls falls below the threshold fluence.

Authors 9

1. Manuel Henn

   University of Stuttgart

   Affiliation as printed

   Univ. Stuttgart (Germany)

2. Lukas Schneller

   University of Stuttgart

   Affiliation as printed

   Graduate School of Advanced Manufacturing Engineering GSaME (Germany)

   Univ. Stuttgart (Germany)

3. Daniel Holder

   University of Stuttgart

   Affiliation as printed

   Univ. Stuttgart (Germany)

4. Dennis Haasler Aachen Fraunhofer-Institut für Lasertechnik ILT

   Fraunhofer Institute for Laser Technology

   Affiliation as printed

   Fraunhofer-Institut für Lasertechnik ILT (Germany)

5. Marc Hummel Aachen Fraunhofer-Institut für Lasertechnik ILT

   RWTH Aachen University · Fraunhofer Institute for Laser Technology

   Affiliation as printed

   Fraunhofer-Institut für Lasertechnik ILT (Germany)

   RWTH Aachen Univ. (Germany)

6. Felix Beckmann
   Affiliation as printed

   Institute of Materials Physics (Germany)

7. Julian P. Moosmann
   Affiliation as printed

   Institute of Materials Physics (Germany)

8. Christian Hagenlocher

   University of Stuttgart

   Affiliation as printed

   Univ. Stuttgart (Germany)

9. Thomas G. Graf

   University of Stuttgart

   Affiliation as printed

   Univ. Stuttgart (Germany)