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Turbine blades are often individual, complex shaped components made of demanding materials. In this study it is investigated, if such components can be made of special steels like Duplex or Superduplex steels by a precise build-up of single weld seams produced with a new innovative welding process called "CMT". Although shape giving welding is well...
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... built up between the tip of the filler wire electrode and the groove, has to melt down the wire electrode, to fuse the components and to establish a common weld pool. For protecting the arc against the atmosphere a gas shielding is necessary -this could be done mainly by an external gas supply or more seldom by a special type of filler wire. In Fig. 1 the scheme of a modern, inverter-based GMAW power source is shown. Depending on the applied amperage and voltage, provided by the welding machine, different arc modes, e. g. short arc, spray arc or pulsed arc, can be set up. But this process cannot be used only for joining -also overlaying can be done in a very easy manner, if the ...
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... filler metal for this trials a typical filler metal for joining Duplex Stainless Steels, Böhler CN 22/9 N-IG was used. The mechanical properties of the all weld metal are shown in table 1; the delta ferrite content of the all weld metal is between 30 -60 FN. The microstructure of a Duplex Stainless Steel blade made by CMT/MAM is shown in Fig. 11; Fig. 10 shows the position of the samples and the examined area. As it can be seen, it is a typical Duplex Stainless Steel weld microstructure. The measured delta ferrite content of 34-36 FN is within the proposed values of the filler metal supplier. Till now, the microstructural investigation gave no evidence for pores and slag inclusions and ...
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Investigations of modal parameters for a mistuned packet of turbine blades due to lacing wire damage are reported using analytical and numerical studies with a simplified model. The turbine blade is assumed to be an Euler-Bernoulli beam connected with a lacing wire which is modeled as a mass less linear elastic spring. Thus, the blade is considered...
Citations
... From the available welding processes currently used in WAAM, CMT is gaining interest among researchers. Being a variant of GMAW this process not only produces weld beads with good quality, stable arc, a lower heat input than other DED processes and nearly spatter-free depositions [8] but it is also easy to operate and combine with a robotic system [9]. P.M Cerqueira et [10]. ...
Wire + Arc Additive Manufacturing (WAAM®) is an additive manufacturing (AM) process capable of producing near net shape parts while reducing costs and thus gathering increased attention from researchers and manufacturers. Although a significant amount of work has already been published relating to the WAAM processing of stainless steels, it was mainly focused on austenitic stainless steels, with martensitic grades still lacking investigation. AISI 410 is a martensitic stainless steel that, due to its high hardness, demonstrates high wear resistance, being used in parts requiring high resistance to abrasion. Processing this material by WAAM allows for the creation of near net shape parts, leading to a reduction in machining, while at the same time allowing the creation of complex geometries which would be difficult, or outright impossible to obtain otherwise. In this work the effects of different processing parameters on WAAM processed AISI 410 steel, using Cold Metal Transfer (CMT) welding equipment, were investigated, as well as different deposition strategies for the fabrication of a test artifact using an AM software. It was demonstrated that it is possible to process AISI 410 steel by WAAM using an AM software to define deposition strategies and parameters based on the part design and previous experimental trials. The goal to deposit a complex part with high hardness and tensile strength, especially attractive properties to parts requiring high resistance to wear was achieved.
... Exceptional arc stability, drop-by-drop controlled material deposition, low heat input, nearly spatter-free application, and high process tolerance are typical CMT process characteristics. Therefore, CMT has been selected as a promising arc-based AM method [27,47,48]. The successful application of CMT for the WAAM of various materials such as steels [41,46,49], titanium- [50,51], nickel-based [52][53][54], magnesium- [55][56][57], and aluminium alloys [58,59] has already been demonstrated. ...
... This corresponds to a reduction in the number of layers by about 10% in the CMT process as compared to the MAG process. The material transfer that takes place in the CMT process at a lower energy level is responsible for the lower welding temperature, i.e. waiting time, and less dilution with the substrate/preceding layers [47,73]. Due to its low heat input and dilution, CMT seems more suitable for AM than standard GMAW processes [47]. ...
... The material transfer that takes place in the CMT process at a lower energy level is responsible for the lower welding temperature, i.e. waiting time, and less dilution with the substrate/preceding layers [47,73]. Due to its low heat input and dilution, CMT seems more suitable for AM than standard GMAW processes [47]. The lower heat input and dilution ensure continuous deposition and prevent the overheating or excessive remelting of previously deposited material [47]. ...
... CMT provides a lowenergy MIG welding process with an oscillating wire electrode at high frequencies. By synchronising the power signal and wire oscillation, deposition of exactly one droplet of metal with each oscillation is possible (Gerhard et al. 2014;Rodriguez et al. 2018). CMT is capable of high deposition rates with low heat input Wang, Xue, and Wang 2019), lower spatter (Kazanas et al. 2011;Radel et al. 2019), reduced porosity (Cong, Ding, and Williams 2015) and reduced distortion (Elitzer et al. 2022). ...
Wire Arc Directed Energy Deposition (WA-DED) also known as Wire Arc Additive Manufacture (WAAM) is a niche additive manufacturing technique for metals that is increasingly offering a competitive advantage to traditional forging and casting methods. Characteristics of WA-DED are high deposition rates and feedstock that is inexpensive compared to powder processes, making it highly efficient for manufacture of large components. This paper reviews WA-DED as a technique for large component manufacture by assessing aspects of the process scalability. Arc processes are compared in terms of their production characteristics showing the relative suitability of each power source. Additional in-situ processes have been identified that can alleviate defects and improve mechanical performance. Investigation of process planning for WA-DED has revealed the potential for material savings that can be achieved by preventing accumulation of errors throughout manufacture. The major finding is that additional in-situ processes and process planning combined with a closed loop feed forward control system can significantly improve the process in terms of mechanical performance, geometric repeatability and resolution. Additionally, it was found that although the degree of isotropy of mechanical performance is commonly investigated, research into the heterogeneity of mechanical performance is limited, and does not assess tensile properties at different locations within deposited material.
... This, in turn, can result in significant cost savings and shorter lead times. Cold metal transfer (CMT) has proven to be a promising WAAM method due to the low heat input and dilution characteristics of the process [26][27][28][29][30][31][32]. This lower heat input and dilution enables continuous deposition and prevents ''burnthrough" on already deposited material [26]. ...
... Cold metal transfer (CMT) has proven to be a promising WAAM method due to the low heat input and dilution characteristics of the process [26][27][28][29][30][31][32]. This lower heat input and dilution enables continuous deposition and prevents ''burnthrough" on already deposited material [26]. Using the high-end CMT process, it is possible to control the arc and droplet transfer accurately to create more sophisticated structures [26,29]. ...
... This lower heat input and dilution enables continuous deposition and prevents ''burnthrough" on already deposited material [26]. Using the high-end CMT process, it is possible to control the arc and droplet transfer accurately to create more sophisticated structures [26,29]. ...
In the present study, the application and tailoring of the alloy composition of chromium martensitic hot-work steels using metal cored wires (MCW) for wire arc additive manufacturing (WAAM) in a modified short-circuit metal transfer process is demonstrated. The nickel content was varied and the alloys were fabricated as tubular-cored wires with various powder fillings. By recording the material transfer at high speed during processing, evidence was gathered indicating the suitability of the fabricated cored wires for WAAM. Optimized process parameters were identified by taking a Design of Experiment (DoE) approach and additive manufacturing (AM) structures were fabricated from the chromium martensitic hot-work tool steel alloys. The microstructure and mechanical properties of the parts were subsequently characterized. The phase fraction of the polygonally shaped delta ferrite could be reduced and microstructural refinement could be achieved by adding nickel to the investigated hot-work tool steel. In addition to molybdenum-enriched precipitates that covered the grain boundaries, randomly scattered non-metallic inclusions and oxides were observed. Modifying the microstructure by adding nickel also affects the mechanical properties of the product: an increase in hardness, impact toughness and yield strength as the nickel content increased in the AM structures fabricated by WAAM was observed.
... Many researchers gave their contribution to this topic (such as in [3] and in [4]) and nowadays many CAM software are available in the research field; these are able to calculate deposition toolpaths both for three and five axis machines or 6-dof robots. As said, WAAM is a 3D welding based additive manufacturing technology, that could use different welding technologies: Metal Inert Gas (MIG) [5], Tungsten Inert Gas (TIG) [6] and Plasma Arc Welding (PAW) [7]. This paper concentrates on the MIG version of WAAM that is the most versatile one, especially to implement five axis deposition [8] [9], since in this case, the shape of the deposed bead is not influenced by the deposition direction. ...
... If the resulting image still contains some non-zero pixels, the frame is discarded (4), otherwise it is passed to the next processing step. If the frame has not been discarded, a binary threshold with a lower value is applied (5). The resulting image is further processed to extract all the interesting features. ...
Wire Arc Additive Manufacturing (WAAM) is an emerging technology to produce metallic components thanks to its high deposition rate and low cost compared to other technologies. One step to make the WAAM technology reliable is to achieve a stable process control that can avoid collapse of the part during deposition caused by an excessive thermal input that may bring to a collapse of the part. To avoid that, dwells must be introduced in the production phase that slow down the productivity and introduce start-and-stop operations that often are sources of defects. This paper presents an easy-to-use and cost-effective monitoring system for WAAM as a first step to overcome this issue. The proposed technique uses an optical camera to acquire images of the deposited bead that are analysed to determine the condition of the bead itself to control the process. The general idea is to create the data background to support the implementation of a future closed loop control of WAAM, able to keep constant the deposition conditions and make the process stable. An experimental test case is presented to demonstrate that the proposed system is effectively able to monitor the process, extracting significative data form the acquired pictures that can be used to modify the process parameters to keep the deposition stable.
... One of these additive manufacturing processes, which is expected to produce similarly high component strengths as conventionally manufactured components, is wire arc additive manufacturing (WAAM; see [3]). For special applications, such as turbine blades made of titanium or high-grade steels, production with WAAM is already established and accepted, see e.g., [4]. Applications can also be found in the aerospace industry, [2], in marine and architecture, as well as in nuclear power 1. ...
In this study, the monotonic and cyclic material properties of steel material of medium static strength produced additively in the wire arc additive manufacturing (WAAM) process were investigated. This investigated material is expected to be particularly applicable to the field of mechanical engineering, for which practical applications of the WAAM process are still pending and for which hardly any characteristic values can be found in the literature so far. The focus of the investigation was, on the one hand, to determine how the material characteristics are influenced by the load direction in relation to the layered structure and, on the other hand, how they are affected by different interlayer temperatures. For this purpose, monotonic tensile tests were carried out at room temperature as well as at elevated temperatures, and the cyclic material properties were determined. In addition, the hardness of the material and the residual stresses induced during production were measured and compared. In addition to the provision of characteristic properties for the investigated material, it was aimed to determine the extent to which the interlayer temperature influences the strength characteristics, since this can have a considerable influence on the production times and, thus, the economic efficiency of the process.
... The wire tip in the specially designed torch controlled by a powerful motor can reach a high frequency of forward and backward movement (up to 130 Hz) during welding. This can reduce the energy input to a minimum degree [14]. ...
The effect of arc modes on the microstructure and tensile properties of 5183 aluminium alloy fabricated by cold metal transfer (CMT) processes has been thoroughly investigated. Heat inputs of CMT processes with three arc modes, i.e., CMT, CMT advance (CMT+A), and CMT pulse (CMT+P), were quantified, and their influence on the formation of pores were investigated. The highest tensile strength was found from samples built by the CMT+A process. This agrees well with their smallest average pore sizes. Average tensile strengths of CMT+A arc mode-built samples were 296.9 MPa and 291.8 MPa along the horizontal and vertical directions, respectively. The difference of tensile strength along the horizontal and vertical directions of the CMT+P and CMT samples was mainly caused by the pores at the interfaces between each deposited layer. The successfully built large 5183 aluminium parts by the CMT+A arc mode further proves that this arc mode is a suitable mode for manufacturing of 5183 aluminium alloy.
... What's more, CMT is a spatter-free droplet transfer process conducted via precise control of current parameters and wire movement during the short-circuit transfer. A specially designed welding torch holding a very powerful motor can reach a high frequency forward and backward movement (up to 130 Hz) of the wire during welding, which can reduce the energy input to a minimum degree [13]. ...
In this research, four different welding arc modes including conventional cold metal transfer (CMT), CMT-Pulse (CMT-P), CMT-Advanced (CMT-ADV), and CMT pulse advanced (CMT-PADV) were used to deposit 2219-Al wire. The effects of different arc modes on porosity, pore size distribution, microstructure evolution, and mechanical properties were thoroughly investigated. The statistical analysis of the porosity and its size distribution indicated that the CMT-PADV process gave the smallest pore area percentage and pore aspect ratio, and had almost no larger pores. The results from optical microscopy, scanning electron microscopy, and fractographic morphology proved that uniform and fine equiaxed grains, evenly distributed Al2Cu second phase particles were formed during the CMT-PADV process. Furthermore, the X-ray diffraction test ascertained that the CMT-PADV sample had the smallest lattice parameter and the highest solute Cu content. Besides, the tensile strength could reach 283 MPa, the data scattering was the smallest, and the strength scattering of the sample in the horizontal direction was the shortest. In addition, the strength properties were nearly isotropic, with only 5 MPa difference in the vertical and horizontal directions. The above mentioned results indicated that the mechanical properties of 2219 aluminum alloy was improved using the CMT-PADV arc mode.
... Als Beispiel für den erfolgreichen Einsatz des MSG-Schweißens zur additiven Fertigung ist die Turbinenfertigung der Firma Andritz Hydro (MicroGuss™) zu nennen. Hierbei wird ein robotergeführter geregelter Kurzlichtbogenprozess (CMT der Firma Fronius) eingesetzt, um Peltonturbinenschaufeln aus weichmartensitischem Stahl X3CrNiMo13-4 herzustellen [52]. Dabei wird an Stelle des üblicherweise verwendeten Gussbauteils eine Verbundkonstruktion aus Schmiedekern und aufgeschweißten Bechern eingesetzt. ...
Der Trend im modernen B2C Handel geht zu immer kürzeren Lieferzeiten bei gleichzeitig gesteigerter Individualität der Produkte. Auch Nachhaltigkeitsfaktoren und Umweltbilanz spielen eine immer größere Rolle. Eine Möglichkeit diesen Herausforderungen in Städten der Zukunft (smart cities) zu begegnen ist die Organisation von Serienfertigungen in dezentrale angeordneten „Microfactories“. Additive Fertigungsverfahren gewährleisten dabei eine hohe Flexibilität, Individualität der produzierten Produkte und eine „on demand“ Verfügbarkeit. In unserer Arbeit beleuchten wir, welche Probleme für das Produktionskonzept der Microfactory gelöst werden müssen. Welche Prozesse sind nötig, von der Erstellung des Designs zur sicheren Weitergabe an eine Microfactory, der Fertigung und der Qualitätssicherung der Bauteile? Wie können vorhandene Ressourcen durch Dienstleister und Makerspaces in Deutschland, aber auch weltweit sinnvoll genutzt und standardisiert werden? Außerdem geben wir einen Ausblick auf additive Produktionsverfahren, welche in Zukunft die mögliche Produktvielfalt von Microfactories erhöhen könnten.
... CMT was chosen as promising arc based additive manufacturing method [12]- [14], predestined through its low heat input and dilution characteristics [12]. ...
... CMT was chosen as promising arc based additive manufacturing method [12]- [14], predestined through its low heat input and dilution characteristics [12]. ...
... The lower heat input and dilution ensures continuous deposition and to prevent already deposited material from "burn through" [12]. ...
The goal of this study was to find suitable welding parameters for a quick and economic repair of forging tools. Therefore geometries made of hot working tool steel were generated using wire based Cold Metal Transfer (CMT) procedure. Welding and geometric parameters were varied and their influence on the mechanical characteristics of the welded structure was investigated.
The microstructure of the manufactured geometries was examined by light optical microscopy (LOM). The mechanical properties were determined by hardness testing and tensile testing.
The automated process combines low heat input and a precise metal deposition with low dilution. This promises a near net shape manufacturing with reduced subsequent machining time, which reduces total costs of the produced or repaired part.
