Sebastian Thieme

High performance corrosion resistant coatings by novel coaxial cold- and hot-wire laser cladding methods

In the last few years, coaxial laser heads have been developed with centric wire feeding equipment, which enables the laser processing of complex-shaped objects in various applications. These newly developed laser heads are being used particularly in laser brazing experiments in the automotive industry. This study presents experimental results of using a coaxial laser head for cold- and hot-wire cladding application. The coaxial wire cladding method has significant improvements compared with the off-axis wire cladding method such as independence of the travel direction, alignment of the wire to the laser beam, and a reduced number of controlling parameters. These features are important to achieve high quality coatings. Cladding tests were conducted on mild steel with a coaxial laser wire welding head using Ni-based Inconel 625 and Thermanit 2509 super duplex stainless steel solid wires in order to determine the properties of the cladding process and the coatings deposited. The corrosion resistance of the ...

High-performance laser cladding with combined energy sources

In the field of laser additive manufacturing, modern hybrid technologies offer advantageous solutions for combining the high quality level of laser surface claddings with the industrys economical requirements regarding productivity and energy efficiency. The technical approach is to supply energy sources in two fundamentally different ways. First, welding material in the form of wire is directly heated, i.e., by electrical resistance, almost to its melting point and is fed to the process region simultaneously with the laser beam. A newly developed coaxial wire head allows for omni-directional welding operation and, thus, the use of wire even for complex surface claddings as well as layer-by-layer fabrication of metallic parts. Second, an additional energy source is used to heat the substrate in order to compensate for the heat conduction losses. This technical variant is suitable for use with both wire and powder as deposition materials. Additionally, heating and cooling gradients can be precisely adjust...

Process characteristics in high-precision laser metal deposition using wire and powder

Laser-based additive manufacturing (AM) technologies such as laser metal deposition have been introduced in various fields of applications. Laser metal deposition is not only used for the fabrication of complete new parts but also for the purpose of repair and redesign. Therefore, weld beads with dimensions above 1 mm were mostly used in the past. In some cases, bead widths can even exceed 10 mm or more. However, the build-up of filigree parts by means of submillimeter structures has gained interest during the last several years. Fabrication of structures with small dimensions requires different process modifications along the process chain. This includes not only general process strategies but also adjusted system components. The changed process yields material deposition of varying geometries possibly used in aerospace, space, medical technology, and microtooling. Additionally, it can also be used in the repair of worn or damaged microparts. In this paper, the aforementioned process modifications are sh...

Generative Manufacturing and Repair of Metal Parts through Direct Laser Deposition Using Wire Material

In the field of Laser Additive Manufacturing, modern wire-based laser deposition techniques offer advantageous solutions for combining the high quality level of layer-by-layer fabrication of high value parts with the industry’s economical requirements regarding productivity and energy efficiency. A newly developed coaxial wire head allows for omni-directional welding operation and, thus, the use of wire even for complex surface claddings as well as the generation of three-dimensional structures. Currently, several metallic alloys as steel, titanium, aluminium, and nickel are available for the generation of defect-free structures. Even cored wires containing carbide hardmetals can be used for the production of extra wear-resistant parts. Simultaneous heating of the wire using efficient electric energy increases significantly the deposition rate and energy efficiency. Examples of application are light-weight automotive parts, turbine blades of Nickel super alloys, and complex inserts of injection moulds.

Laser-based fabrication with Ti- and Ni-base superalloys

Laser-based technology of direct metal deposition has matured into an industrially well established technique for precise coating deposition and additive manufacturing. By means of dedicated nozzle systems, suitable process equipment as well as well customized manufacturing strategies, the fabrication of miniaturized, but even very large components becomes feasible. This includes the use of powder as well as wire for the added material.Fostered by high demands, e. g. in the field of stationary gas turbines or jet engines, the state of the art has to be extended especially in the direction of lightweight fabrication as well as increased temperature performance of processed materials. However, from a materials perspective, these materials are often difficult to handle by liquid phase processing.Due to their beneficial material properties needed to fulfill the high performance requirements from the industry, titanium and nickel based superalloys have recently attracted considerable attention. Processing these materials, which are often characterized by a high brittleness and small process windows, is rather challenging and thus requires a customized laser-based fabrication process. The present paper shows recent advances to bring these materials into real applications through laser-based processing. This not only includes modifications of the laser process and the equipment itself, but also the support by hybrid processing, e. g. induction as well as closed loop process control.The paper will also highlight the importance of indepth materials knowledge and process understanding for highest quality 3D direct laser deposition.Laser-based technology of direct metal deposition has matured into an industrially well established technique for precise coating deposition and additive manufacturing. By means of dedicated nozzle systems, suitable process equipment as well as well customized manufacturing strategies, the fabrication of miniaturized, but even very large components becomes feasible. This includes the use of powder as well as wire for the added material.Fostered by high demands, e. g. in the field of stationary gas turbines or jet engines, the state of the art has to be extended especially in the direction of lightweight fabrication as well as increased temperature performance of processed materials. However, from a materials perspective, these materials are often difficult to handle by liquid phase processing.Due to their beneficial material properties needed to fulfill the high performance requirements from the industry, titanium and nickel based superalloys have recently attracted considerable attention. Processing thes...

Processing and properties of duplex stainless steel coatings manufactured by coaxial hot-wire laser cladding

Duplex stainless steels are used for example in pulp and paper industry, chemical plants and offshore platforms. The advantages of duplex stainless steels are high resistances to pitting corrosion, stress corrosion cracking and corrosion fatigue. The experimental tests using Thermanit 2509 super duplex wire were performed with coaxial laser wire cladding head. Thermanit 2509 is austenite-ferrite stainless steel Fe-25Cr-10Ni-4Mo with high amount of alloying contents with excellent corrosion resistance. Corrosion properties of duplex hot-wire laser coatings were investigated by the critical pitting temperature (CPT) test. CPT values of duplex laser coating specimens were measured nearly consistent with 2507 wrought duplex steel. Microstructure phases of laser duplex coatings were investigated and compared to the objective 50-50% austenite-ferrite ratio.