Laserumschmelzstrukturierung zur Beseitigung von Welligkeit oder Herstellen von Strukturen auf metallischen Oberflächen
Beschichtungs- und Oberflächentechnik
Herstellung und Eigenschaften von Funktionsmaterialien
Zusammenfassung der Projektergebnisse
The main objectives of "DeConStruc" were to create predetermined structures or to eliminate existing undesirable structures by "destructive interference" and to gain the required process understanding. One possible application for structuring non-periodic structures is the elimination of residual waviness on additive manufactured parts after laser polishing. It was found that with laser polishing the surface roughness of LPBF parts up to a spatial wavelength of 0.5 mm can be reduced by ~96%, while waviness can only be reduced by ~55%. To further reduce waviness, different approaches to structure and de-structure non-periodic structures like the residual waviness on LPBF manufactured parts were explored. One approach for the generation of complex structures is superposition of sinusoidal structures of different structure wavelength, laser power amplitude and phase. Overall, it was estimated that the effort for generating and calculating the laser power modulation for structuring a desired non-periodic target structure with the superposition approach is very extensive. Therefore, deviating from the project plan, a new approach was developed, based on the extended understanding of structure formation generated by the conducted simulations. The target structure is integrated and then transformed to a laser power modulation. To test the new integral approach a profile cross-section of the laser polished LPBF surface was structured and de-structured. For the laser power amplitude of PA = 13.5 W and four passes the smallest structural deviation of Pa(∆) = 15.9% was determined. For de-structuring with the laser power amplitude of PA = 13.5 W and four passes a waviness reduction of 62% can be achieved. The resulting waviness is Wa = 0.51 µm. Waviness could therefore be reduced more effective than with laser polishing. The integral approach was also investigated for the structuring und destructuring of areas. The most effective processing strategy is structuring with four passes and changing the scanning direction from x-direction to y-direction for each pass. The waviness of the initial structure and the actual structure are with WaActual = 1.806 µm and WaTarget = 1.817 µm comparable. For de-structuring, the highest smoothing could be achieved with a laser power amplitude corresponding to 70% of the laser power amplitude used for structuring. A possible reason for this is the smoothing effect caused by the surface tension in the liquid phase. The waviness after de-structuring can be determined to Wa = 0.812 µm. Therefore, a waviness reduction of 55% can be achieved with de-structuring. The integration approach for the structuring and de-structuring of complex structures developed is a promising solution for the elimination of residual waviness on LPBF manufactured parts after laser polishing. However, for industrial implementation, the new findings must first be transferred to free-form surfaces and real components. Fist test for structuring of free-form surfaces were carried out. Processing of an inclined surface and of interfacing edges was investigated. Increasing the inclination of the surface leads to an increase of the angle of incidence of the laser radiation. It was found that the amplitude of the structure decreases with increasing angle of incidence. To avoid a decrease in amplitude with an increase of the angle of incidence, the average laser power and the laser power amplitude must be adjusted with 1/cos(ß). Interfacing edges should always be placed at the valleys of the structure and adjacent test fields should always be structured in the same scanning direction and not in opposing scanning directions. In this project, a method for ablation-free structuring of non-periodic structures was developed. With this method, the number of structures that can be created was significantly increased. In addition, the structuring by laser remelting of 3D parts was developed. As a result, it is expected that structuring by laser remelting will be able to replace other industrial structuring processes in the future.
Projektbezogene Publikationen (Auswahl)
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Numerical and experimental investigation on formation of surface structures in laser remelting for additive-manufactured Inconel 718. Surface and Coatings Technology, 403 (2020, 12), 126370.
Temmler, A.; Pirch, N.; Luo, J.; Schleifenbaum, J.H. & Häfner, C.L.
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Shape Deviation of Surface Structures Produced by WaveShape (Structuring by Laser Remelting) on Ti6Al4V and a Method for Deviation Reduction. Micromachines, 12(4), 367.
Oreshkin, Oleg; Panov, Daniil; Kreinest, Laura; Temmler, André & Platonov, Alexander
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Structuring by laser remelting as a method for waviness reduction on additive manufactured parts. Procedia CIRP, 111(2022), 689-692.
Kreinest, Laura; Schober, Benedikt; Willenborg, Edgar & Schleifenbaum, Johannes Henrich
