Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

Filters

8
4
Reset filters

Settings
Now showing 1 - 8 of 8
  • Publication
    3D laser metal deposition: Process steps for additive manufacturing
    ( 2018)
    Graf, Benjamin
    ;
    Marko, Angelina
    ;
    Petrat, Torsten
    ;
    Gumenyuk, Andrey
    ;
    Rethmeier, Michael
    Laser metal deposition (LMD) is an established technology for two-dimensional surface coatings. It offers high deposition rates, high material flexibility, and the possibility to deposit material on existing components. Due to these features, LMD has been increasingly applied for additive manufacturing of 3D structures in recent years. Compared to previous coating applications, additive manufacturing of 3D structures leads to new challenges regarding LMD process knowledge. In this paper, the process steps for LMD as additive manufacturing technology are described. The experiments are conducted using titanium alloy Ti-6Al-4V and Inconel 718. Only the LMD nozzle is used to create a shielding gas atmosphere. This ensures the high geometric flexibility needed for additive manufacturing, although issues with the restricted size and quality of the shielding gas atmosphere arise. In the first step, the influence of process parameters on the geometric dimensions of single weld beads is analyzed based on design of experiments. In the second step, a 3D build-up strategy for cylindrical specimen with high dimensional accuracy is described. Process parameters, travel paths, and cooling periods between layers are adjusted. Tensile tests show that mechanical properties in the as-deposited condition are close to wrought material. As practical example, the fir-tree root profile of a turbine blade is manufactured. The feasibility of LMD as additive technology is evaluated based on this component.
  • Publication
    3D laser metal deposition in an additive manufacturing process chain
    ( 2017)
    Graf, Benjamin
    ;
    Gumenyuk, Andrey
    ;
    Rethmeier, Michael
    Laser metal deposition (LMD) is an established technology for two-dimensional surface coatings. It offers high deposition rates, high material flexibility and the possibility to deposit material on existing components. Due to these features, LMD has been increasingly applied for additive manufacturing of 3D structures in recent years. Compared to previous coating applications, additive manufacturing of 3D structures leads to new challenges regarding LMD process knowledge. In this paper, the process chain for LMD as additive manufacturing technology is described. The experiments are conducted using titanium alloy Ti-6Al-4V and Inconel 718. Only the LMD nozzle is used to create a shielding gas atmosphere. This ensures high geometric flexibility, although issues with the restricted size and quality of the shielding gas atmosphere arise. In the first step, the influence of process parameters on the geometric dimensions of single weld beads is analysed based on design of experiments and statistical evaluation. The results allow adjusting the weld bead dimensions for the specific component geometry. In the second step, features of a 3D build-up strategy for high dimensional accuracy are discussed. For this purpose, cylindrical specimens consisting of more than 200 layers are built. Welding of multiple layers on top of each other leads to heat accumulation. Consequently, the molten pool is increased and weld bead height and width are changed. Furthermore, cooling times are prolonged. The build-up strategy has to be adjusted to deal with these issues. Process parameters, travel paths and cooling breaks between layers are varied. Temperatures during the deposition process are measured with pyrometer and thermography. The specimens are analysed with metallurgic cross sections, x-ray and tensile test. Tensile tests show that mechanical properties in the as-deposited condition are close to wrought material. The results are used to design guidelines for a LMD build-up strategy for complex components. As reality test, parts of a gas turbine burner and a turbine blade are manufactured according to these build-up strategies. Build-up rate, net-shape and microstructure of these demonstrative components are evaluated. This paper is relevant for industrial or scientific users of LMD, who are interested in the feasibility of this technology for additive manufacturing.
  • Publication
    Temperature generation of different travel path strategies to build layers using Laser Metal Deposition
    ( 2017)
    Petrat, Torsten
    ;
    Graf, Benjamin
    ;
    Winterkorn, René
    ;
    Gumenyuk, Andrey
    ;
    Rethmeier, Michael
    Laser Metal Deposition offers the chance to build near net shape parts. The temperature evolution within the process has an influence on track and layer geometries. There are special travel path strategies required to produce near net shape components and reduce shape deviation resulting of error propagation. This paper deals with the temperature progression of individual layers and the maximum heating of deeper substrate regions. Spiral and zig-zag strategies are examined. The investigations are carried out using S235JR as substrate and 316L as powder material. The influence of different strategies on temperature evolution is discussed. The results from the experiments show that various production strategies are associated with different temperature fields. Furthermore, the extent of the temperature variations of layer strategies and layer position are strongly dependent on the production direction. These results demonstrate the importance of developing suitable build-up strategies for parts of complex shape to ensure a stable process with constant temperature as well as even layers.
  • Publication
    Laser metal deposition as repair technology for a gas turbine burner made of Inconel 718
    ( 2016)
    Petrat, Torsten
    ;
    Graf, Benjamin
    ;
    Gumenyuk, Andrey
    ;
    Rethmeier, Michael
    Maintenance, repair and overhaul of components are of increasing interest for parts of high complexity and expensive manufacturing costs. In this paper a production process for laser metal deposition is presented, and used to repair a gas turbine burner of Inconel 718. Different parameters for defined track geometries were determined to attain a near net shape deposition with consistent build-up rate for changing wall thicknesses over the manufacturing process. Spot diameter, powder feed rate, welding velocity and laser power were changed as main parameters for a different track size. An optimal overlap rate for a constant layer height was used to calculate the best track size for a fitting layer width similar to the part dimension. Deviations in width and height over the whole build-up process were detected and customized build-up strategies for the 3D sequences were designed. The results show the possibility of a near net shape repair by using different track geometries with laser metal deposition.
  • Publication
    Laser-Pulver-Auftragschweißen zum additiven Aufbau komplexer Formen
    ( 2015)
    Petrat, Torsten
    ;
    Graf, Benjamin
    ;
    Gumenyuk, Andrey
    ;
    Rethmeier, Michael
    Das Laser-Pulver-Auftragschweißen als additives Fertigungsverfahren ermöglicht einen endformnahen Aufbau von Bauteilen. Ein Zielkonflikt besteht zwischen der Forderung nach hoher Aufbaurate und hoher Endformnähe, welcher von der Schweißraupengröße wesentlich beeinflusst wird. In dieser Veröffentlichung wird das Laser-Pulver-Auftragschweißen eingesetzt, um komplexe Formen additiv aufzubauen. Am Beispiel eines Tannenbaumprofiles werden unterschiedliche Einflussfaktoren dargestellt. Dazu gehören die Raupengeometrie, die Überlappung einzelner Raupen, die Verwendung unterschiedlicher Aufbaustrategien und die Teilung des Gesamtkörpers in Teilkörper. Der Zielkonflikt wird durch die Herstellung von Probekörpern mit unterschiedlichen Steigungswinkeln an den Seitenflächen verdeutlicht. Die Ergebnisse zeigen eine verbesserte Endformnähe in Bereichen flacher Steigung beim Einsatz kleiner Schweißraupen. Im Vergleich dazu erlauben die Schweißparameter der großen Raupen eine 5-fach höhere Aufbaurate. Bei einer Raupenüberlappung kleiner und großer Raupengeometrien innerhalb einer Lage treten Anbindungsfehler auf. Strategien zur Behebung dieses Fehlers durch Anpassung der Schweißreihenfolge werden in dieser Veröffentlichung aufgezeigt. Diese Erfahrungen werden genutzt, um einen Gesamtkörper aus Teilkörpern unterschiedlicher Raupengeometrien zu fertigen.
  • Publication
    Design of experiments for laser metal deposition in maintenance, repair and overhaul applications
    ( 2013)
    Graf, Benjamin
    ;
    Ammer, Stefan
    ;
    Gumenyuk, Andrey
    ;
    Rethmeier, Michael
    Modern and expensive parts lead to an increasing demand for maintenance, repair and overhaul (MRO) technologies. Instead of part replacement, MRO technologies are economically advantageous throughout the life cycle. Laser metal deposition as modern MRO technology can be used to repair cracks or protect damaged surfaces with a hard facing layer. It is necessary to adjust weld bead profile to the specific task. For this purpose, Design of Experiment (DoE) has a high potential to decrease experimental effort. In this paper, a full factorial design is used to determine the effect of process parameters on the geometric dimensions of the weld bead. The paper is of interest to engineers working with laser metal deposition as well as DoE methods.
  • Publication
    Laser metal deposition as repair technology for stainless steel and titanium alloys
    ( 2012)
    Graf, Benjamin
    ;
    Gumenyuk, Andrey
    ;
    Rethmeier, Michael
    In a repair process chain, damaged areas or cracks can be removed by milling and subsequently be reconditioned with new material deposition. The use of laser metal deposition has been investigated for this purpose. The material has been deposited into different groove shapes, using both stainless steel and Ti-6Al-4 V. The influence of welding parameters on the microstructure and the heat affected zone has been studied. The parameters have been modified in order to achieve low heat input and consequently low distortion as well as low metallurgical impact. Finally, an evaluation of the opportunities for an automatized repair process is made.
  • Publication
    Laser metal deposition as repair technology for stainless steel and titanium alloys for petrochemicals industry
    ( 2012)
    Graf, Benjamin
    ;
    Gumenyuk, Andrey
    ;
    Rethmeier, Michael
    In a repair process chain for petrochemicals industry, damaged areas or cracks can be removed by milling and subsequently be reconditioned with new material deposition. The use of laser metal deposition has been investigated for this purpose. The material has been deposited into different groove shapes, using both stainless steel and Ti-6Al-4V which are widely used in petrochemicals industry. The influence of welding parameters on the microstructure and the heat affected zone has been studied. The parameters have been modified in order to achieve low heat input and consequently low distortion as well as low metallurgical impact. Finally, an evaluation of the opportunities for an automatized repair process is made with the aim of future application in petrochemicals industry.