Ingomar Kelbassa

Photodegradation of methyl orange under visible light by micro-nano hierarchical Cu2O structure fabricated by hybrid laser processing and chemical dealloying.

Micro-nano hierarchical structure on the substrate was fabricated by a hybrid approach including laser deposition, laser ablation and chemical dealloying. The structure consists of micro bumps with a width of 50 μm and a height of 100 μm, and nanoporous structures with a size of 70-150 nm on the micro bumps. XRD and XPS results confirm that these hierarchical structures were made of Cu(2)O. For use in comparison, three additional structures with feature size in milliscale, microscale, and nanoscale were also prepared respectively by the proposed methods. Under visible light, the micro-nano structure exhibited the best performance of photodegradation. It is the result of the large specific surface and the catalytic reaction driven by the cuprous oxides.

Densification behavior, microstructure evolution, and wear property of TiC nanoparticle reinforced AlSi10Mg bulk-form nanocomposites prepared by selective laser melting

Selective laser melting (SLM), due to its unique additive manufacturing processing philosophy, demonstrates a high potential in producing bulk-form nanocomposites with novel nanostructures and enhanced properties. In this study, the nanoscale TiC particle reinforced AlSi10Mg nanocomposite parts were produced by SLM process. The influence of “laser energy per unit length” (LEPUL) on densification behavior, microstructural evolution, and wear property of SLM-processed nanocomposites was studied. It showed that using an insufficient LEPUL of 250 J/m lowered the SLM densification due to the balling effect and the formation of residual pores. The highest densification level (>98% theoretical density) was achieved for SLM-processed parts processed at the LEPUL of 700 J/m. The TiC reinforcement in SLM-processed parts experienced a structural change from the standard nanoscale particle morphology (the average size 75–92 nm) to the relatively coarsened submicron structure (the mean particle size 161 nm) as the app...

In situ measurement of plasma and shock wave properties inside laser-drilled metal holes

High-speed imaging of shock wave and plasma dynamics is a commonly used diagnostic method for monitoring processes during laser material treatment. It is used for processes such as laser ablation, cutting, keyhole welding and drilling. Diagnosis of laser drilling is typically adopted above the material surface because lateral process monitoring with optical diagnostic methods inside the laser-drilled hole is not possible due to the hole walls. A novel method is presented to investigate plasma and shock wave properties during the laser drilling inside a confined environment such as a laser-drilled hole. With a novel sample preparation and the use of high-speed imaging combined with spectroscopy, a time and spatial resolved monitoring of plasma and shock wave dynamics is realized. Optical emission of plasma and shock waves during drilling of stainless steel with ns-pulsed laser radiation is monitored and analysed. Spatial distributions and velocities of shock waves and of plasma are determined inside the holes. Spectroscopy is accomplished during the expansion of the plasma inside the drilled hole allowing for the determination of electron densities.

High-temperature oxidation performance and its mechanism of TiC/Inconel 625 composites prepared by laser metal deposition additive manufacturing

The laser metal deposition (LMD) additive manufacturing process was applied to produce TiC/Inconel 625 composite parts. The high-temperature oxidation performance of the LMD-processed parts and the underlying physical/chemical mechanisms were systematically studied. The incorporation of the TiC reinforcement in the Inconel 625 improved the oxidation resistance of the LMD-processed parts, and the improvement function became more significant with increasing the TiC addition from 2.5 wt. % to 5.0 wt. %. The mass gain after 100 h oxidation at 800 °C decreased from 1.4130 mg/cm2 for the LMD-processed Inconel 625 to 0.3233 mg/cm2 for the LMD-processed Inconel 625/5.0 wt. % TiC composites. The oxidized surface of the LMD-processed Inconel 625 parts was mainly consisted of Cr2O3. For the LMD-processed TiC/Inconel 625 composites, the oxidized surface was composed of Cr2O3 and TiO2. The incorporation of the TiC reinforcing particles favored the inherent grain refinement in the LMD-processed composites and, therefor...

Beam shaping of laser diode radiation by waveguides with arbitrary cladding geometry written with fs-laser radiation

Waveguides with arbitrary cross sections are written in the volume of Al(2)O(3)-crystals using tightly focused femtosecond laser radiation. Utilizing a scanning system with large numerical aperture, complex cladding geometries are realized with a precision around 0.5 µm and a scanning speed up to 100 mm/s. Individual beam and mode shaping of laser diode radiation is demonstrated by varying the design of the waveguide cladding. The influence of the writing parameters on the waveguide properties are investigated resulting in a numerical aperture of the waveguides in the range of 0.1. This direct laser writing technique enables optical devices which could possibly replace bulky beam shaping setups with an integrated solution.

Increased Wear and Oxidation Resistance of Titanium Aluminide Alloys by Laser Cladding

A process layout for laser cladding of layers on substrates of titanium aluminides using state-of-the-art and modified (additions of Si and TiB2) TiAl alloys is presented. The process involves a preheating of the samples to reduce thermal stresses and cladding in an inert gas atmosphere with an oxygen content lower than 30 ppm. These conditions lead to crack free layers and low surface oxidation. Microstructure and hardness of the layers are investigated. The abrasive wear resistance of the cladded layers in comparison to the base material is tested with promising results. Finally results of the oxidation behavior are shown and prove the increased performance of modified TiAl layers in comparison to the base material.

Applying Functionally Graded Materials by Laser Cladding: a cost-effective way to improve the Lifetime of Die-Casting Dies

The lifetime and economic methods of improving the lifetime of a die-casting die are key factors for the die-casting industry since the global competition and the competition with other production techniques have increased significantly. The article depicts the approach, technical realization, latest results and process limitations of the INNOGRAD research project. Here, powder-based laser-cladding is applied to combine two materials as a functionally graded material. By applying gradient structures it is possible to fit the material to the predominant type of exposure, resulting in an increase in the lifetime of die-casting dies.

Drilling with fiber lasers

For drilling holes such as cooling holes in tool forms or turbine blades with diameters from 100 µm up to 1.5 mm flash lamp pumped laser sources e.g. slab lasers are commonly used. These laser sources have peak powers of several kW at pulse durations from microseconds up to milliseconds with a high beam quality. Due to the beam quality, small spot sizes and intensities greater than 106 W/cm2 are achieved. The mean power of these laser sources is in the range of some mW up to several hundred W rather small.So far fiber lasers are not used for laser drilling due to small peak powers and intensities. Meanwhile, fiber lasers with a scalable output power of 1 W up to 50 kW in multimode or up to 10 kW in single-mode with a beam quality of M² < 6 in the multimode and M² < 1.1 in single-mode are offered in cw. Furthermore fiber lasers with a beam quality of M² < 6 are offered with a maximum peak power of 6 kW in a pulsed operation mode. With these fiber lasers drilling seems to be possible. Thus laser drilling with fiber lasers is investigated and compared to flash lamp pumped Nd:YAG lasers.For drilling holes such as cooling holes in tool forms or turbine blades with diameters from 100 µm up to 1.5 mm flash lamp pumped laser sources e.g. slab lasers are commonly used. These laser sources have peak powers of several kW at pulse durations from microseconds up to milliseconds with a high beam quality. Due to the beam quality, small spot sizes and intensities greater than 106 W/cm2 are achieved. The mean power of these laser sources is in the range of some mW up to several hundred W rather small.So far fiber lasers are not used for laser drilling due to small peak powers and intensities. Meanwhile, fiber lasers with a scalable output power of 1 W up to 50 kW in multimode or up to 10 kW in single-mode with a beam quality of M² < 6 in the multimode and M² < 1.1 in single-mode are offered in cw. Furthermore fiber lasers with a beam quality of M² < 6 are offered with a maximum peak power of 6 kW in a pulsed operation mode. With these fiber lasers drilling seems to be possible. Thus laser drilling wi...

Fabrication of nanoparticulate reinforced metal matrix composites by laser cladding

The nanoparticulate reinforced metal matrix composites (nPRMMCs) can further improve the ductility and fracture toughness of conventional microscale PRMMCs. The uniform dispersion of nanosized hard particles in the matrix is vital due to their strong tendency to agglomerate. This paper summarizes the state-of-the-art fabrication process of nPRMMCs by laser cladding via both ex-situ route and in-situ route. Concerns have been focused on the uniform dispersion of nanoparticles and their interface bonding with the matrix. The current challenges and future developments are discussed. This summarization will be helpful for the further research on the fabrication and applications of nPRMMCs.

Additive manufacturing of a blade-integrated disk by laser metal deposition

Currently, high value Class 1 jet engine components such as BLISKs (Blade-Integrated diSKs) are manufactured by time and cost-prohibitive conventional techniques, such as five-axis milling, linear friction welding and electro chemical machining. The investigation within the Fraunhofer Cluster of Innovation “TurPro” qualifies Laser Metal Deposition (LMD) as a new “green manufacturing” method for nickel and titanium alloy-based BLISKs. Feasibility studies and subsequent process development towards a first additive IN 718 BLISK mock-up are presented. Parameter windows for laser powers up to 10 kW have been investigated to attain high deposition rates of up to 9,000 mm3/min for track widths between 2 mm and 4 mm. Using a zoom optics, track width of the tool path can be adjusted during the process to the airfoil geometry and a near-net shape built up can be achieved. Process time of two minutes for the additive manufacture of a near-net shape single blade was achieved. When the blade receives the appropriate heat treatment, its static and dynamic material properties were found to be approximate to forged components.Currently, high value Class 1 jet engine components such as BLISKs (Blade-Integrated diSKs) are manufactured by time and cost-prohibitive conventional techniques, such as five-axis milling, linear friction welding and electro chemical machining. The investigation within the Fraunhofer Cluster of Innovation “TurPro” qualifies Laser Metal Deposition (LMD) as a new “green manufacturing” method for nickel and titanium alloy-based BLISKs. Feasibility studies and subsequent process development towards a first additive IN 718 BLISK mock-up are presented. Parameter windows for laser powers up to 10 kW have been investigated to attain high deposition rates of up to 9,000 mm3/min for track widths between 2 mm and 4 mm. Using a zoom optics, track width of the tool path can be adjusted during the process to the airfoil geometry and a near-net shape built up can be achieved. Process time of two minutes for the additive manufacture of a near-net shape single blade was achieved. When the blade receives the appropriate h...