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Item type:Publication, Access status: without files , Functionalization of sapphire surfaces using fs-laser radiation and selective etching(Laser Inst. of America, 2011-10); ; ; The change of surface properties, e.g. wettability and optical properties of sapphire surfaces, by direct writing of large ripple areas using a technique called "In-volume Selective Laser Etching" (ISLE) is demonstrated. In the process the sample is irradiated and by that modified/nano structured in the focal volume of the laser beam. The laser radiation is focused and scanned on the surface of the sample. Afterwards the sample is chemically wet etched using 48 % hydrofluoric acid (HF) to remove the modified material. In this paper the direct structuring of large ripple areas on transparent dielectrics up to 11 mm in diameter is shown for the first time. First achieved results will be discussed and an outlook to future applications will be given. The surface patterning is carried out with a 1.5 W FCPA laser system from IMRA.Publicationtype: Conference Paper15 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Development of a model for prediction of material properties of laser cladded inconel 718 as related to porosity in the bulk material(Laser Inst. of America, 2011-10); ; ; High value jet engine components such as compressor blades or BLade Integrated DiSKS (BLISKS) are manufactured by time and cost-prohibitive conventional techniques, such as five-axis milling, linear friction welding and electro chemical machining. This project within the Fraunhofer Cluster of Innovation "TurPro" qualifies the Laser metal deposition process (LMD) as a new "green manufacturing" method for nickel and titanium alloy-based BLISKs. Thus, a significant increase of the deposition rate (factor 10 or higher) is of interest. Aiming for a process certification of additive manufacturing of BLISK blades, using conventionally manufactured disks as a substrate, quality assurance and predictable material properties remain a major concern. In this paper, the distribution of pore sizes of laser deposited Inconel 718 (IN 718) is investigated, using laser powers of up to 5.5 kW and deposition rates of up to 7000 mm3/min. Using quantitative image analysis, defining sub-sets and applying extreme value and logarithmic Gaussian distribution, the pore-size-distribution in the bulk material can be described with merely 4 statistical parameters. Based on these parameters, the ultimate tensile strength (UTS) of a cladded sample can be estimated with an accuracy of approx. 250 - 300 MPa.Publicationtype: Conference Paper14 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Waveguides and markings inside transparent materials by fs-laser radiation(Laser Inst. of America, 2011-10); ; ; Localized, three-dimensional refractive index changes are generated by focused femtosecond laser radiation (λ= 1045 nm, ≈ 500 fs) in the volume of transparent materials. Depending on the scanning direction and laser parameters both waveguides and colorful markings are produced in a depth of d = 150-200 μm below the surface of glass materials. The micro morphology of the irradiated structures is studied with light microscopy revealing a homogenous and crack-free modification. Depending on the angle of light incidence wavelengths of the visible light are diffracted at structured grids leading to bright colors in the observer's eyes. The optical guiding properties of the waveguides are investigated by far field measurements obtaining their numerical aperture. By using femtosecond double pulses instead of single pulses an increase in the numerical aperture of the fabricated waveguides is achieved. Results regarding the characteristics of double pulse waveguides in fused silica as well as examples for colorful marking in glass and crystals are presented.Publicationtype: Conference Paper11 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Additive manufacturing of a blade-integrated disk by laser metal deposition(Laser Inst. of America, 2011-10); ; ; 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.Publicationtype: Conference Paper14 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Characterization of micro/macrostructure of laser cladded inconel 718 with increased deposition rates as related to the mechanical properties(Laser Inst. of America, 2011-10); ; ; 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. This project within the Fraunhofer Cluster of Innovation "TurPro" qualifies the LMD process as a new "green manufacturing" method for nickel and titanium alloy-based BLISKs. Quality assurance and predictable material properties remain a major concern when aiming for a process certification of additive manufacturing of BLISK blades. This paper presents the results of a microstructure investigation of laser cladded IN 718 using increased deposition rates of up to 7000 mm3/min. Presented are the ternary relations between process parameters, dendrite arm spacing and resulting mechanical properties with respect to niobium segregation.Publicationtype: Conference Paper12 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Advantages of laser metal deposition by using zoom optics and MWO (Modular Welding Optics)Laser Metal Deposition (LMD) using powder additive materials has been successfully introduced into industry for the use in wear and corrosion applications and as repairs of e.g. turbine components, moulds, and dies and is increasingly being employed for varied 3-D applications as well. For a variation of the track width an adaptation of the laser beam diameter in the interaction zone is mandatory. The zoom optics presented in this paper enables a variation of the laser beam diameter for producing different track widths during the process of machining. Compared to the conventional optics, the extensive adjustment of a powder nozzle to the working point is unnecessary. The variation of the laser beam diameters is generated by adjusting the lens positions. In the interaction zone the laser beam diameter can be varied from d = 0.6 mm to d = 2.4 mm. The power density distribution produced corresponds as closely as possible to a top-hat distribution, which is best for Laser Metal Deposition. With this new concept designed zoom optics can be applied with different laser sources.Publicationtype: Conference Paper9 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Drilling with fiber lasers(Laser Inst. of America, 2011-10); ; ; For drilling holes such as cooling holes in tool forms or turbine blades with diameters from 100 ?m 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.Publicationtype: Conference Paper19