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High precision and high aspect ratio laser drilling: Challenges and solutions

: Uchtmann, H.; He, C.; Gillner, A.

Postprint urn:nbn:de:0011-n-3855524 (1.8 MByte PDF)
MD5 Fingerprint: 54a233c9fd7e86e4306cd7714179d0e6
Erstellt am: 19.4.2016

Dorsch, F. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
High-Power Laser Materials Processing: Lasers, Beam Delivery, Diagnostics, and Applications V : San Francisco, California, 16-18 February 2016
Bellingham, WA: SPIE, 2016 (Proceedings of SPIE 9741)
ISBN: 978-1-628-41976-4
Paper 974106, 12 S.
Conference "High-Power Laser Materials Processing - Lasers, Beam Delivery, Diagnostics, and Applications" <5, 2016, San Francisco/Calif.>
Konferenzbeitrag, Elektronische Publikation
Fraunhofer ILT ()

Laser drilling is a very versatile tool to produce high accuracy bores in small and large geometries using different technologies. In large and deep hole drilling laser drilling can be found in drilling cooling holes into turbomachinery components such as turbine blades. In micro drilling, the technology is used for the generation of nozzles and filters. However, especially in macro drilling, the process often causes microstructure changes and induces defects such as recast layers and cracks. The defects are caused by the melt dominated drilling process by using pulse durations in the range of some 100 μm up to a few ms. A solution of this problem is the use of ultrashort pulsed laser radiation with pulse durations in the range of some 100 fs up to a few ps, however with the disadvantage of long drilling times. Thus, the aim of this work is to combine the productive process by using ms pulsed fiber laser radiation with subsequent ablation of existing recast layers at the hole wall by using ultrashort pulsed laser radiation. By using fast scanning techniques the recast layer can be avoided almost completely. With a similar technology also very small hole can be produced. Using a rotating dove prism a circular oscillation of the laser spots is performed and holes are drilled at intervals in 1 mm thick stainless steel (1.4301) by ultra-short laser pulses of 7 ps at 515 nm. The formation of hole and the behavior of energy deposition differ from other drilling strategies due to the helical revolution. The temporal evolution of the hole shape is analyzed by means of SEM techniques from which three drilling phases can be distinguished.