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Tailored forming is used to produce hybrid components in which the materials used are locally adapted to the different types of physical, chemical and tribological requirements. In this paper, a Tailored Forming process chain for the production of a hybrid shaft with a bearing seat is investigated. The process chain consists of the manufacturing steps laser hot-wire cladding, cross-wedge rolling, turning and deep rolling. A cylindrical bar made of mild steel C22.8 is used as the base material, and a cladding of the martensitic valve steel X45CrSi9-3 is applied in the area of the bearing seat to achieve the strength and hardness required. It is investigated how the surface and subsurface properties of the hybrid component, such as hardness, microstructure and residual stress state, change within the process chain. The results are compared with a previous study in which the austenitic stainless steel X2CrNiMo19-12 was investigated as a cladding material. It is shown that the residual stress state after hot forming depends on the thermal expansion coefficients of the cladding material.

Deposition welding of components using the laser metal deposition (LMD) process is a proven method of creating 3D structures. It is used for the manufacturing of components, the repair of machine parts and for cladding. Up to now, claddings have mainly been investigated in the flat welding position. Some investigations on deposition welding in vertical orientation are available with different processes. For the cladding of large components, welding in the vertical direction offers advantages. So far, there are no investigations on the LMD process with coaxial wire feeding when welding in vertical direction. Therefore, in this study, the influence of the welding direction, i.e., vertical down and vertical up weld seams, and the influence of the welding speed are investigated. Single weld seams, claddings and a wall are welded. A stable welding process could be achieved for a welding speed parameter window of 100 to 1000 mm/min. The results show that there is a statistical correlation between the welding direction and the waviness of the weld seams. Vertical up weld seams have a lower waviness. Another influence on the waviness is the welding speed. As the welding speed decreases, the waviness increases. The weld seam geometry is strongly dependent on the welding direction. With vertical down weld seams, the width and height of the weld seam vary depending on the distance welded. This can be attributed to the influence of the gravitational force. Vertical up weld seams, on the other hand, have a more uniform shape.

Claddings are used to protect areas of components that are exposed to particular chemical, physical or tribological stresses. The aim when developing a cladding process is to achieve a cladding with low waviness in order to reduce the amount of machining required. Computational models and FEA simulations can be used to determine process parameters for claddings with low rework including a prediction of the height and width of a single weld seam aswell as the development of welding strategies. In this paper empirical models describing the geometry of single weld seams on a substrate manufactured with a coaxial laser hot-wire cladding process are investigated for three steel wire materials and different welding parameters. The coordinates of surface points of the weld seams were detected using a laser scanning microscope and post-processed by a self-created script. In order to describe the cross sectional shape of the weld seams, the parameters of parabolic, cosinusiodal or circular arc model functions are derived from the surface data using a fitting algorithm. For the tested wire materials, an effect of the wire material on the shape of the weld seam was not observed. The investigations also show that regardless of the varied welding parameter set or wire material, a circular model function appears to be the most suitable model shape for describing the cross sectional weld seam geometry in coaxial laser metal deposition with hot-wire. The regression residua using a circular arc model function ranged from 18.9 $$\upmu$$ μ m to 34.6 $$\upmu$$ μ m, which indicates a good approximation.

The Tailored Forming process chain is used to manufacture hybrid components and consists of a joining process or Additive Manufacturing for various materials (e.g. deposition welding), subsequent hot forming, machining and heat treatment. In this way, components can be produced with materials adapted to the load case. For this paper, hybrid shafts are produced by deposition welding of a cladding made of X45CrSi9-3 onto a workpiece made from 20MnCr5. The hybrid shafts are then formed by means of cross-wedge rolling. It is investigated, how the thickness of the cladding and the type of cooling after hot forming (in air or in water) affect the properties of the cladding. The hybrid shafts are formed without layer separation. However, slight core loosening occurres in the area of the bearing seat due to the Mannesmann effect. The microhardness of the cladding is only slightly effected by the cooling strategy, while the microhardness of the base material is significantly higher in water cooled shafts. The microstructure of the cladding after both cooling strategies consists mainly of martensite. In the base material, air cooling results in a mainly ferritic microstructure with grains of ferrite-pearlite. Quenching in water results in a microstructure containing mainly martensite.

Due to the increased integration of functions, many components have to meet high and sometimes contradictory requirements. One way to solve this problem is Tailored Forming. Here, hybrid semi-finished products are manufactured by a joining or cladding process, which are then hot-formed and finished. For the design of hybrid components for a possible later industrial application, knowledge about properties of hybrid components is required. In this paper it is investigated how the respective process steps of the Tailored Forming process chain change the surface and subsurface properties of the applied cladding layer. For this purpose, shafts made of unalloyed steel are provided with a high-alloy austenitic steel X2CrNiMo19-12 cladding by laser hot-wire cladding. Subsequently, hot forming is carried out by cross-wedge rolling and the finishing by turning and deep rolling. After each process step, the subsurface properties of the cladding such as microstructure, hardness and residual stress state are examined. Thus, the influence of different process steps on the subsurface properties in the process chain of manufacturing hybrid shafts can be analyzed. This knowledge is necessary for the specific adjustment of defined properties for a required application behavior.

Locally adapted properties within a machine component offer opportunities to increase the performance of a component by using high strenght materials where they are needed. The economic production of such hybrid components on the other hand represents a major challenge. The new tailored forming process chain, which is developed within the collaborative research center (CRC 1153) represents a possible solution to produce hybrid components. This is made possible by the use of pre-joined hybrid semi-finished products made from two different steel alloys, which are subsequently formed. The semi-finished products can be manufactured for example by means of deposition welding. Due to a thermal mechanical treatment, an overall higher component strength of the joining zone can be achieved. The deposition welding processes can be used to generate a cladding on a base material. During the welding, one of the most difficult tasks is to reduce the amount and size of pores in the joining zone. These pores can reduce the strength in the joining zone of the welded parts. However, additional pores can occur in the intermediate zone between the substrate and the cladding. In the presented study, the influence of the forming process on the closing of pores in the cladding and in the intermediate zone was investigated. Therefore, cylindrical specimen were extracted in longitudinal direction of the welding track by wire-cut eroding. These welding tracks are manufactured by plasma-transferred arc welding of AISI 52100 on a base plate made of AISI 1015. Further, specimens were prepared transversely, so that the base material, the intermediate layer, and the welded material are axially arranged in the specimen. The prepared specimen were checked for pores by means of scanning acoustic microscopy. Subsequently, an uniaxial compression test was carried out with various degrees of deformation and the two specimen designs were examined again for pores. A microstructure analysis was carried out after each step. The investigations show that there is a need for a minimum degree of deformation to reduce pores in the welded material. However, this required plastic strain cannot be achieved in the welded material of the hybrid specimen, which is a result of the homogeneous temperature distribution in the specimen. The homogeneous temperature distribution leads to different flow properties in the specimen, which means that the main plastic deformation is taking place in the base material.

Coaxial laser wire directed energy deposition promises a direction-independent buildup of near net shape geometries and surface coatings. Simultaneously introducing two different wire materials into the processing zone enables the production of in situ alloyed or even functionally graded structures. Functionally graded materials and in situ alloyed parts aim to extend the range of materials for development purposes. This work covers the intermixing behavior of two wire materials with greatly differing element contents. Therefore, a multiple diode coaxial laser (DiCoLas) processing head is used consisting of three individually controllable fiber coupled laser diodes with a combined maximum output power of 660 W and a wavelength of 970 nm. Two metal wires, 1.4430 and 1.4718, with a diameter of 0.8 mm are provided simultaneously to the processing zone under an incidence angle of 3.5° to the processing head's middle axis. The DiCoLas processing head enables a stable welding process with good dimensional accuracy of the single welding geometries. Single weld seams and multiple-layer structures are investigated to cover the intermixing behavior for different applications of additive manufacturing. Thermal images of the melting process provide an insight into the melting behavior of the two wire materials and the formation of the weld seam. energy-dispersive x-ray-mappings and line scans display the element distribution of the main alloying elements along the seam cross section. Furthermore, hardness measurements examine the hardness progression along the multiple-layer welding structures showing an even progression of the hardness values over the entire cross section.

Laser-assisted double-wire welding with a nontransferred arc is used for cladding workpieces. The wire material is melted by an arc and dropped onto the substrate, where a laser beam is oscillated by a galvanometer scanner to achieve bonding of the melt with good contact angles that do not result in undercuts. In this study, the galvanometer scanner was replaced by a beam shaping optics generating a line with a width of 1.2 mm and a length of 9.1 mm. Based on Design of Experiments, the laser power was varied in a range from 1500 to 2000 W and the welding speed in a range from 600 to 800 mm/min. Single weld beads of AISI 316L were welded onto a mild steel of AISI 1024 according to a full factorial design at three repetitions per parameter set. The paper examines whether the contact angles of the weld beads produced with the line optics are comparable to those obtained by oscillating the laser beam. In addition, the dilution of the material with the substrate was determined in micrographs. The results show that the bonding to the substrate can be achieved. The parameter window for the laser power with beam shaping line optics is different from that with the oscillated laser beam. The required laser power is 1.5–2 times greater.

Additive Manufacturing of glass opens up new possibilities for the design and integration of optical components. By varying the shape and size of optical elements, optical systems specifically adapted to various applications can be fabricated cost-effectively. The Laser Glass Deposition (LGD) process uses a CO2 laser with a wavelength of 10.6 μm to locally generate temperatures above 2000 °C in fused silica fibers. This enables the Additive Manufacturing and Rapid Prototyping of glass by melting and then layer-by-layer deposition of fibers. However, these high temperatures can result in very high residual stress in the material. The development of a coaxial LGD process aims for a more uniform heating of the glass fiber during the printing process in order to enable a direction-independent process and to reduce the residual stresses within the printed components. In this work, a novel concept for the coaxial LGD process and its successful experimental application is presented. Further, a numerical simulation model is developed to describe the temperature distribution in the glass fiber during the coaxial LGD process. Based on experimental results and on the numerical simulation, the potentials and challenges of the coaxial LGD process are discussed.

Die Anwesenheit von Sauerstoff bewirkt beim Laser Powder Bed Fusion (LPBF) eine Bauteilversprodung und fuhrt zu Oxidschichten mit verschlechterten Benetzungseigenschaften des Grundwerkstoffes. Zur Inertisierung der Prozessatmosphare wird deshalb beim LPBF herkommlicherweise Argon eingesetzt, wobei der Restsauerstoffgehalt bei Normaldruck weiterhin kritische Oxidationen bewirkt.

Aufgrund der hohen Kosten von speziellen Pulverwerkstoffen beim Laser-Auftragschweisen zeigt sich konventionelle Systemtechnik hinsichtlich der Pulverausnutzung nachteilig: Bei zentraler Laserstrahlfuhrung und einer Pulverzufuhr uber eine Ringspaltduse tritt erhohter Pulververlust auf, da der Pulverstrahldurchmesser den des Schmelzbades auf dem Werkstuck deutlich ubersteigt. Besonders bei filigranen Strukturen im Mikrometer-Bereich tritt ein Pulververlust von bis zu 90 % ohne mogliche Pulverruckgewinnung auf.

The use of additive manufacturing methods in research and industry has led to the possibility of designing more compact, light and low-cost assemblies. In the field of laser development, new opportunities resulting from additive manufacturing have rarely been considered so far. We present a compact, lightweight solid-state amplifier system for low-power applications where the optomechanical components are manufactured completely additive via Fused Filament Fabrication (FFF). The amplifier system is based on a Nd:YVO4-crystal pumped with an external, fiber-coupled diode at a wavelength of 808nm and a maximum output power of 3 W. The seed source is a Nd:YVO4-crystal based solid-state laser with an emission wavelength of 1064 nm. The commercial optical components, such as lenses and crystal, are firmly imprinted via FFF in the optomechanics and thus secured against misalignment. Additionally, sensor technology for temperature measurement is implemented into the devices. The use of FFF, in which the components are printed from polymers, results in a lightweight yet stable construction. We have shown, that optical components can be imprinted without adding mechanical stress. To increase the mechanical and thermal robustness of the system different types of polymers as well as post process treatments are tested and the use of Laser Metal Deposition for this application is investigated. The thermal stability of the printed structures is evaluated to determine the maximum power level of the system without damaging the polymer-optomechanics. Furthermore, output power, optical-to-optical efficiency, beam pointing, and beam shape are measured for several on- and off-switching processes as well as long-term operation.

The service life of rolling contacts is dependent on many factors. The choice of materials in particular has a major influence on when, for example, a ball bearing may fail. Within an exemplary process chain for the production of hybrid high-performance components through tailored forming, hybrid solid components made of at least two different steel alloys are investigated. The aim is to create parts that have improved properties compared to monolithic parts of the same geometry. In order to achieve this, several materials are joined prior to a forming operation. In this work, hybrid shafts created by either plasma (PTA) or laser metal deposition (LMD-W) welding are formed via cross-wedge rolling (CWR) to investigate the resulting thickness of the material deposited in the area of the bearing seat. Additionally, finite element analysis (FEA) simulations of the CWR process are compared with experimental CWR results to validate the coating thickness estimation done via simulation. This allows for more accurate predictions of the cladding material geometry after CWR, and the desired welding seam geometry can be selected by calculating the cladding thickness via CWR simulation. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

Das koaxiale Laser-Draht-Auftragschweisen ist ein Fertigungsverfahren fur das Drucken generativer Strukturen und Beschichten bzw. Reparieren von Oberflachen. Anforderungen an die Systemtechnik liegen neben guten Schweisergebnissen besonders in der Robustheit gegenuber mechanischen, thermischen und chemischen Einflussen sowie einer guten Handhabbarkeit.

Inhalt: Moderne Massivbauteile werden herkömmlich aus Monomaterialien gefertigt. Viele Bauteile besitzen dabei Funktions- und Strukturbereiche, welche durch unterschiedliche Beanspruchungsprofile sehr unterschiedliche Anforderungen an den Konstruktionswerkstoff stellen. Somit ermöglicht das eingesetzte Material oft nur einen Kompromiss hinsichtlich der geforderten Materialeigenschaften und der Leistungsfähigkeit des Bauteils. Im Sonderforschungsbereich 1153 „Tailored Forming“ an der Leibniz Universität Hannover (LUH) werden neue Prozessketten zur Realisierung hoch belastbarer hybrider Massivbauteile entwickelt. In Zusammenarbeit des Instituts für Werkstoffkunde (IW) und des Instituts für Maschinenkonstruktion und Tribologie (IMKT) wurden hybride Lagerscheiben zum Einsatz als Axial-Zylinderrollenlagern entwickelt. Diese wurden mittels Plasma-Pulver-Auftragschweißen (PPA) aus Vergütungsstahl hergestellt (Bild 1) und anschließend bezüglich Ihrer Wälzfestigkeit untersucht. Diese Untersuchungen dienen als Grundlage zur Evaluierung von Leistungsfähigkeit und Qualität des Beschichtungsprozesses sowie der Materialeigenschaften. Mit ersten hybrid hergestellten Rohlingen werden Maschinenelemente gefertigt, um die Eignung des Prozesses für industrielle Anwendungen zu bewerten. Abstract: Modern solid components are conventionally manufactured from monomaterials. Many components are equipped with functional and structural areas, which have to fulfil various demands regarding the construction material due to different stress profiles. Thus, the applied material offers a trade-off concerning the required material properties and the performance of the component. The Collaborative Research Center 1153 „Tailored Forming“ at Leibniz Universität Hannover (LUH) is developing new process chains for the realization of highly resilient hybrid solid components. In cooperation with the Institute of Materials Science (IW) and the Institute of Machine Design and Tribology (IMKT), multi-material bearing discs were developed for use as cylindrical roller thrust bearings. These were produced by plasma powder deposition welding (PPA) from heat treatable steel (Figure 1) on a steel substrate and then tested under rolling contact loads. These investigations serve as a basis for evaluating the performance and quality of the coating process as well as the material properties. In this publication, the above concept was proven for first hybrid produced workpieces in order to assess the suitability of the process for industrial applications.

The “laser assisted double wire welding with nontransferred arc” utilizes an arc burning between two laterally fed wires combined with a laser beam source and beam guidance. By oscillating in the transverse direction, the necessary thermal energy is put locally in a targeted manner and results in a homogeneous temperature profile overall. This leads to the uniform melting of the substrate surface so that complete fusion is achieved over the cross section. The linear oscillation of the laser beam is characterized by a sinusoidal function whose extrema are located in the edge regions of the melt pool and, due to the low velocity, pulls the melt pool apart. In this work, the influence of laser parameters on the seam geometry of generatively manufactured structures is investigated. These include pendulum amplitude, defocusing, and laser beam position of a disk laser with a wavelength at 1030 nm. This enables the selective adjustment of the seam width and seam height, thus allowing to generate structures of 316L at application rates of up to 21 kg/h using 400 A current for the arc [A. Barroi, J. Hermsdorf, U. Prank, and S. Kaierle, “A novel approach for high deposition rate cladding with minimal dilution with an arc – laser process combination,” Phys. Proc. 41, 249–254 (2013)]. In order to illustrate the effect of the laser beam on the melt pool, the processes are visually and thermally documented with a thermos camera and 300 fps. Furthermore, the influence of preheating by laser radiation on the seam quality and geometry is shown. The topology and geometry of the individual seams are determined using a confocal microscope. Thus, a minimal irregular seam of approximately 10 mm beginning at a defocusing of −1 mm and a laser beam position of −3.5 mm in the melt pool is achieved.

Within the framework of the bilateral CORNET projects MeTexCom and MeTexCom2, new approaches were developed and tested to improve the adhesion strength of metal textile composites, with a focus on the targeted roughening of aluminum surfaces and the development of new acoustically insulating nonwovens. The metal textile composites were produced by melting thermoplastic components of the textile composites without a separately applied adhesive.For improved adhesion strength between metal and textile, roughness was generated on the metal surface by means of a novel arc treatment by an anodic polarized TIG process or a cw (continuous wave) fiber laser process. On the one hand, the goal was to produce uniformly rough, untercut surface structures in micro-and nanodimension by means of a highly dynamic arcing process. On the other hand, a similar approach was pursued with the cw laser method by using a single-mode as well as a multi-mode laser.

Es bestand das Ziel, einen Laser-Drahtauftragsschweiskopf zu entwickeln, der sowohl fur die generative Fertigung, als auch zum Auftragen von Verschleisschutzschichten eingesetzt werden kann. Dieser besteht aus einen Grundkorper, an und in welchen die einzelnen Systemkomponenten integriert werden. Zu den Komponenten gehoren grundlegend die optischen Elemente sowie die Schweisduse. Fur die Integration der Einzelteile sind spezielle Halteelemente notwendig. Fur die Duse ist ein spezieller Dusenhalter erforderlich, welcher diese aufnimmt und eine statische Positionierung der Duse relativ zum Gesamtsystem ermoglicht.

The Collaborative Research Centre 1153 (CRC 1153) &ldquo, Process chain for the production of hybrid high-performance components through tailored forming&rdquo, aims to develop new process chains for the production of hybrid bulk components using joined semi-finished workpieces. The subproject B1 investigates the formability of hybrid parts using cross-wedge rolling. This study investigates the reduction of the coating thickness of coaxially arranged semi-finished hybrid parts through cross-wedge rolling. The investigated parts are made of two steels (1.0460 and 1.4718) via laser cladding with hot-wire. The rolling process is designed by finite element (FE)-simulations and later experimentally investigated. Research priorities include investigations of the difference in the coating thickness of the laser cladded 1.4718 before and after cross-wedge rolling depending on the wedge angle &beta, cross-section reduction ∆A, and the forming speed &nu, Also, the simulations and the experimental trials are compared to verify the possibility of predicting the thickness via finite element analysis (FEA). The main finding was the ability to describe the forming behavior of coaxially arranged hybrid parts at a cross-section reduction of 20% using FEA. For a cross-section reduction of 70% the results showed a larger deviation between simulation and experimental trials. The deviations were between 0.8% and 26.2%.

In laser-based powder bed fusion of metals (PBF-LB/M) the presence of oxygen is known to encourage embrittlement and impair the wetting properties of the substrate and solidified material. Conventionally, inert gases like argon are used to reduce the residual oxygen content within the processing atmosphere. However, especially in terms of reactive materials like titanium the remaining oxygen still causes critical oxidations.In this publication, a new approach for obtaining an oxygen-free processing atmosphere is presented. Thereby the argon shielding gas is doped with reactive monosilane to reduce the residual oxygen content to a range comparable to XHV (Extreme High Vacuum, thermodynamic oxygen activity

The present paper describes a new method concerning the production of hybrid bevel gears using the Tailored Forming technology. The main idea of the Tailored Forming involves the creation of bi-metal workpieces using a joining process prior to the forming step and targeted treatment of the resulting joint by thermo-mechanical processing during the subsequent forming at elevated temperatures. This improves the mechanical and geometrical properties of the joining zone. The aim is to produce components with a hybrid material system, where the high-quality and expensive material is located in highly stressed areas only. When used appropriately, it is possible to reduce costs by using fewer high-performance materials than in a component made of a single material. There is also the opportunity to significantly increase performance by combining special load-tailored high-performance materials. The core of the technology consists in the material-locking coating of semi-finished parts by means of plasma-transferred-arc welding (PTA) and subsequent forming. In the presented investigations, steel cylinders made of C22.8 are first coated with the higher-quality heat-treatable steel 41Cr4 using PTA-welding and then hot-formed in a forging process. It could be shown that the applied coating can be formed successfully by hot forging processes without suffering any damage or defects and that the previous weld structure is completely transformed into a homogeneous forming-typical structure. Thus, negative thermal influences of the welding process on the microstructure are completely neutralized.