TY - CONF A1 - Bhadeliya, Ashok T1 - High temperature fatigue crack growth in nickel-based alloys joined by brazing and additive manufacturing N2 - Gas turbine components, made of nickel-based alloys, undergo material damage due to high temperatures and mechanical stresses. These components need periodic replacement to avoid efficiency loss and failure. Repair of these parts is more cost-effective than replacement. State-of-the-art repair technologies, including different additive manufacturing (AM) and brazing processes, are considered for efficient restoration. Materials properties mismatches and/or internal defects in repaired parts may expedite crack initiation and propagation, reducing fatigue life. To understand the crack growth behavior in joining zones and predict the remaining life of repaired components, fatigue crack growth (FCG) tests were conducted on specimens of nickel-based alloys joined via brazing, pre-sintered preforms and AM. The FCG experimental technique was successfully adapted for joined specimens and results indicate that the investigated braze material provides a lower resistance to crack growth. In AM-sandwich specimens, the crack growth rates are significantly reduced at the interface of AM and cast material. T2 - TMS 2024 Annual Meeting & Exhibition CY - Orlando, Florida, USA DA - 03.03.2024 KW - Fatigue crack growth KW - Joined nickel-based alloys PY - 2024 AN - OPUS4-59854 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bhadeliya, Ashok T1 - High temperature fatigue crack growth in nickel-based alloys joined by brazing and additive manufacturing N2 - Nickel-based alloys have been widely used for gas turbine blades owing to their excellent mechanical properties and corrosion resistance at high temperatures. The operating temperatures of modern gas turbines have been increased in pursuit of increased thermal efficiency. Turbine blades are exposed to these high temperatures combined with mechanical stresses, resulting in material damage through creep, fatigue, and other mechanisms. These turbine blades must be regularly inspected and replaced as needed, to prevent the loss of efficiency, breakdown, and catastrophic failure. Repair of the damaged turbine blades is often a more practical and cost-effective option than replacement, as replacement is associated with high costs and loss of material resources. To this end, state-of-the-art repair technologies including different additive manufacturing and brazing processes are considered to ensure efficient repair and optimum properties of repaired components. In any repaired part, materials property-mismatches and/or inner defects may facilitate the crack initiation and propagation and thus reduce the number of load cycles to failure. Therefore, a fundamental understanding of the fatigue crack growth and fracture mechanisms in joining zones is required to enable the prediction of the remaining life of repaired components and to further improve and adapt the repair technologies. Fatigue crack growth experiments have been conducted on SEN (Single Edge Notch) specimens joined via brazing, and pre-sintered Preform (PSP) and multi-materials (casted/printed) specimens layered via additive manufacturing (AM). The experiments were performed at 950 °C and various stress ratios. The crack growth was measured using DCPD (Direct Current Potential Drop) method. The stress intensity factors for joined SEN specimens were calculated using the finite element method and then used to derive the fatigue crack growth curves. Metallographic and fractographic analyses were conducted to get insight into the fracture mechanism. Results show that the experimental technique for fatigue crack growth was successfully adapted and applied for testing joined specimens. Furthermore, the initial tests indicate that the investigated braze filler material provides a lower resistance to crack growth, and bonding defects cause a crack to deviate to the interface of the base material and joining zone. In AM-sandwich specimens, the crack growth rates are significantly reduced when the crack reaches the interface of printed material and casted material. The obtained crack growth data can be used to calibrate a crack growth model, which will further be utilized to predict the remaining life of repaired components. T2 - Fatigue 2024 Conference CY - Cambridge, UK DA - 19.06.2024 KW - Fatigue crack growth KW - Joined nickel-based alloys PY - 2024 AN - OPUS4-60893 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ávila Calderón, Luis T1 - Creep Behavior of Stainless Steel 316L Manufactured by Laser Powder Bed Fusion N2 - Metal additive manufacturing (Metal AM) continues to gain momentum. Many companies explore the manufacturing of innovative products, including components for safety critical applications. Despite the intensive research of recent years, a fundamental understanding of the process‑structure‑property relationships remains challenging due to, i.a., the inherently complex and highly hierarchical microstructures arising from the wide range of build process parameter variability. This contribution presents the resu lts of an experimental study on the creep behavior of an austenitic 316L stainless steel produced by laser powder bed fusion (PBF LB/M/316L) with an emphasis on understanding the effects of microstructure on creep mechanisms. Hot tensile tests and constant force creep tests at 600 °C and 650 °C, X ray computed tomography, as well as optical and electron microscopy were performed. The produced PBF LB/M/316L exhibits a low void population 0.01 %) resulting from the manufacturing parameters used and which a llowed us to understand the effects of other microstructural aspects on creep behavior, e.g., grain morphology and dislocation substructure. A hot‑rolled variant of 316L hwas also tested as a reference. The produced PBF LB/M/316L possesses shorter primary and secondary creep stages and times to rupture and smaller creep stress exponents than the hot‑rolled variant. Overall, the creep damage is more extensive in the PBF LB/M/316L and is characterized as predominantly intergranular. It is considered that the damage behavior is mainly impacted by the formation of precipitates at the grain boundaries combined with their unfavorable orientation. The dislocation substructure and local elemental segregation appear to have a decisive impact on the overall creep behavior. T2 - 16th International Conference on Creep and Fracture of Engineering Materials and Structures CY - Bangalore, India DA - 28.07.2024 KW - AGIL KW - 316L KW - Additive Manufacturing KW - Creep KW - Microstructure evolution PY - 2024 AN - OPUS4-60839 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Camin, B. T1 - Grenzflächenanalyse diffusionsgeschweißter Werkstoffpaarungen Nickel/ Nickelbasis-Superlegierung CMSX-4 N2 - Der Kirkendall-Effekt tritt bei aneinandergrenzenden Metallpaarungen auf, die höheren Temperaturen ausgesetzt sind. Es findet als Funktion von der Temperatur, der Zeit und der Konzentration die Diffusion von Atomen und Leerstellen über die Phasengrenze hinweg statt. Für die Untersuchung des Kirkendall-Effekts wurde mittels Diffusionsschweißens eine Werkstoffpaarung bestehend aus reinem Nickel (Ni) und der Nickelbasis-Superlegierung CMSX-4 hergestellt. Das Gefüge des reinen Nickels ist polykristallin und von CMSX-4 einkristallin. Da der Kirkendall-Effekt neben den oben genannten Parametern zudem von der Kristallorientierung abhängig ist, wurden zwei verschiedene Kristallorientierungen, die [111]- und [001]-Richtungen, gewählt. Aus 3D µ-tomografischen Untersuchungen ist bekannt, dass heiß-isostatisches Pressen (HIP) eine Verringerung der Porosität in CMSX-4 bewirkt, die durch die Erstarrung des Einkristalls bei der Herstellung entsteht [1]. Daher wurden bei den Diffusionsschweißungen Werkstoffpaarungen von reinem Nickel mit drei CMSX-4-Varianten -mit einer γ/γ‘-Mikrostrukturkombiniert: Ni/ CMSX-4 [111], Ni/ CMSX-4 [001] und Ni/ CMSX-4 [001]-HIPed. Die bei der Diffusionsschweißung entstehenden Grenzschichten wurden mittels Stereo-, Licht- und Rasterelektronenmikroskopie sowie EDX-Analysen untersucht. Bei allen Diffusionsschweißungen entstand eine feste Verbindung zwischen den Werkstoffpaarungen. Wie bereits aus [2] bekannt, bildet sich bei allen Proben auf der Rein-Nickelseite der Grenzfläche ein Porensaum aus, während sich auf der CMSX-4-Seite ein γ‘-freie Zone bildet (Abbildung 1). Sowohl die jeweilige Porosität als auch Porengröße des Porensaums der drei Werkstoffpaarungen ist verschieden. Dieses gilt ebenso für die durchschnittliche Schichtdicke der γ‘-freie Zone. Die geringste durchschnittliche Schichtdicke mit 1,45 µm weist die Paarung Ni/ CMSX-4 [001]-HIPed (Abbildung 1b) auf, wobei die Dicke über den Probenquerschnitt konstant ist. Dagegen schwanken die Schichtdicken der γ‘-freie Zonen bei Ni/ CMSX� 4 [111] (Abbildung 1c) zwischen 1,82 – 4,1 µm und Ni/ CMSX-4 [001] (Abbildung 1a) zwischen 1,36 - 4,55 µm. EDX-Messungen (Linescans) von der CMSX-4-Seite über die γ‘-freie Zone bis in den Nickelwerkstoff zeigen den qualitativen Verlauf der Elementkonzentrationen von Nickel und Aluminium (Abbildung 2). Bei allen Werkstoffpaarungen nimmt die Konzentration des Elements Nickel kontinuierlich zu. Während in der Werkstoffpaarung Ni/CMSX-4 [111] der Konzentrationszunahme symmetrisch über die Grenzfläche verläuft, weist Nickel bei den Werkstoffpaarungen Ni/CMSX-4 mit [001]-Orientierung keinen symmetrischer Konzentrationsverlauf auf. Daraus lässt sich schließen, dass hier die Diffusion von Nickel über die Grenzfläche in die γ‘-freie Zone in Abhängigkeit von der Kristallorientierung unterschiedlich stattfindet. Entgegengesetzt diffundiert das Element Aluminium von der CMSX-4-Seite zur Nickelseite, wie sich aus dem ebenfalls unsymmetrischen Elementverlauf schließen lässt. Bemerkenswert ist hier ein Knick, der sich nach einem Steilabfall einem Plateau anschließt, wie im vergrößerten Ausschnitt in Abbildung 2 mit einem roten Pfeil markiert ist. Dieser Verlauf ist von der Kristallorientierung unabhängig und ist auf die bessere Diffusivität von Al im Vergleich zu Ni zurückzuführen. T2 - Materialographie 2024 CY - Berlin, Germany DA - 18.09.2024 KW - Diffusionsschweißen KW - Grenzfläche KW - Nickelbasis-Superlegierung KW - Kirkendall-Effekt PY - 2024 AN - OPUS4-61095 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stargardt, Patrick A1 - Bresch, Sophie A1 - Falkenberg, Rainer A1 - Mieller, Björn T1 - Effect of Reaction Layers on Internal Stresses in Co‐Fired Multilayers of Calcium Manganate and Calcium Cobaltite N2 - A widespread recovery of waste heat requires a cost‐effective production of thermoelectric generators. Thermoelectric oxides are predestined for use at high temperatures. For manufacturing reasons, a multilayer generator design will be easily scalable and cost‐effective. To evaluate the potential of ceramic multilayer technology for that purpose, a multilayer of the promising thermoelectric oxides calcium cobaltite (Ca3Co4O9), calcium manganate (CMO, CaMnO3), and glass–ceramic insulation layers is fabricated. Cracks and reaction layers at the interfaces are observed in the microstructure. The compositions of these reaction layers are identified by energy‐dispersive X‐ray spectroscopy and X‐ray diffraction. Mechanical and thermal properties of all layers are compiled from literature or determined by purposeful sample preparation and testing. Based on this data set, the internal stresses in the multilayer after co‐firing are calculated numerically. It is shown that tensile stresses in the range of 50 MPa occur in the CMO layers. The reaction layers have only a minor influence on the level of these residual stresses. Herein, it is proven that the material system is basically suitable for multilayer generator production, but that the co‐firing process and the layer structure must be adapted to improve densification and reduce the tensile stresses in the CMO. KW - Ceramic multilayers KW - Co-firings KW - Internal stresses PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-601626 DO - https://doi.org/10.1002/pssa.202300956 SP - 1 EP - 9 PB - Wiley VHC-Verlag AN - OPUS4-60162 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zocca, Andrea A1 - Günster, Jens T1 - Towards a debinding-free additive manufacturing of ceramics: A development perspective of water-based LSD and LIS technologies N2 - Ceramic additive manufacturing (AM) requires a complex process chain with various post-processing steps that require expensive machines and special expertise. The key to further market penetration is AM that makes it possible to integrate into an already established ceramic process chain. Most successful AM technologies for ceramics are, however, based on processes that initially have been developed for polymeric materials. For ceramics AM, polymers or precursors are loaded with ceramic particles. This strategy facilitates the entry into AM, however the introduction of organic additives into the ceramic process chain represents a considerable technological challenge to ultimately obtain a ceramic component after additive shaping. In the present communication, two technologies based on ceramic suspensions will be introduced, the “layerwise slurry deposition” (LSD) and “laser induced slip casting” (LIS) technology. Both technologies take advantage of the high packing densities reached by conventional slip casting and moreover enable the processing of fines, even nanoparticles. KW - Additive Manufacturing KW - Ceramic KW - Water-based KW - Debinding KW - Slurry PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-605531 DO - https://doi.org/10.1016/j.oceram.2024.100632 SN - 2666-5395 VL - 19 SP - 1 EP - 13 PB - Elsevier B.V. AN - OPUS4-60553 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hoffmann, Moritz A1 - Stawarczyk, Bogna A1 - Günster, Jens A1 - Zocca, Andrea T1 - Influence of additives and binder on the physical properties of dental silicate glass-ceramic feedstock for additive manufacturing N2 - Objectives The aim of the study was to investigate the impact of organic additives (binder, plasticizer, and the cross-linking ink) in the formulation of water-based feedstocks on the properties of a dental feldspathic glass-ceramic material developed for the slurry-based additive manufacturing technology “LSD-print.” Material and methods Three water-based feldspathic feedstocks were produced to study the effects of polyvinyl alcohol (AC1) and poly (sodium 4-styrenesulfonate) (AC2) as binder systems. A feedstock without organic additives was tested as the control group (CG). Disc-shaped (n = 15) and bar (n = 7) specimens were slip-cast and characterized in the green and fired states. In the green state, density and flexural strength were measured. In the fired state, density, shrinkage, flexural strength (FS), Weibull modulus, fracture toughness (KIC), Martens parameters, and microstructure were analyzed. Disc-shaped and bar specimens were also cut from commercially available CAD/CAM blocks and used as a target reference (TR) for the fired state. Results In the green state, CG showed the highest bulk density but the lowest FS, while the highest FS in the green state was achieved with the addition of a cross-linking ink. After firing, no significant differences in density and a similar microstructure were observed for all slip-cast groups, indicating that almost complete densification could be achieved. The CAD/CAM specimens showed the highest mean FS, Weibull modulus, and KIC, with significant differences between some of the slip-cast groups. Significance These results suggest that the investigated feedstocks are promising candidates for the slurry-based additive manufacturing of restorations meeting the class 1a requirements according to DIN EN ISO 6871:2019–01. KW - Firing KW - 3D-printing KW - Silicate glass-ceramics KW - Debinding PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-600516 DO - https://doi.org/10.1016/j.jmbbm.2024.106563 SN - 1751-6161 VL - 155 SP - 1 EP - 12 PB - Elsevier B.V. AN - OPUS4-60051 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sänger, Johanna A1 - König, N.F. A1 - De Marzi, A. A1 - Zocca, Andrea A1 - Franchin, G. A1 - Bermejo, R. A1 - Colombo, P. A1 - Günster, Jens T1 - Linear volumetric additive manufacturing of zirconia from a transparent photopolymerizable ceramic slurry via Xolography N2 - Advanced ceramics printed with photon-based additive manufacturing deals with anisotropic mechanical properties from the layer-by-layer manufacturing. Motivated by the success in using highly filled transparent slurries containing nanoparticles for powder-based two-photon-polymerization (2PP) for advanced ceramic printing, this works approach is the transfer to Xolography, a volumetric additive manufacturing technology based on linear two-photon excitation and without recoating steps. This paper reports the results of a preliminary investigation optimizing the photocurable slurry to the requirements of Xolography in terms of transparency, over a significantly larger mean free path, compared to 2PP. A feedstock filled with 70 % weight fraction of ceramic particles (∼30 vol%) exhibiting an exceptionally high degree of transparency in the relevant wavelength range of 400–800 nm was prepared from 5 nm zirconia nanoparticles. The high transparency of the photocurable slurry is attributed to the near-monomodal particle size distribution of the zirconia nanoparticles used. KW - Additive manufacturing KW - Xolography KW - Ceramic PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-608908 DO - https://doi.org/10.1016/j.oceram.2024.100655 SN - 2666-5395 VL - 19 SP - 1 EP - 9 PB - Elsevier BV AN - OPUS4-60890 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Günster, Jens T1 - Ceramic Processing with Light N2 - In order to be able to manipulate ceramic powder compacts and ceramic suspensions (slurries) in their volume with light, a minimum transparency of the materials is required. Compared to polymers and metals, ceramic materials are characterized by the fact that they have a wide electronic band gap and therefore a wide optical window of transparency. The optical window generally ranges from less than 0.3 µm to 5 µm wavelength. Therefore, to focus light into the volume of a ceramic powder compact, its light scattering properties need to be tailored. In this study, we present the physical background and material development strategies for the application of two-photon polymerization (2PP), Xolography and selective volumetric sintering for the additive manufacturing of structures in the volume of ceramic slips and green compacts. T2 - CMCEE 14 CY - Budapest, Hungary DA - 18.08.2024 KW - Ceramic KW - Additive manufacturing KW - Light PY - 2024 AN - OPUS4-60892 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sänger, Johanna A1 - Riechers, Birte A1 - Pauw, Brian Richard A1 - Günster, Jens T1 - Transparent feedstocks for photon-based additve manufacturing technologies for powder processing of ceramics N2 - Photon-based additive manufacturing technologies such as SLA, DLP, LCM, moreover volumetric two-photon-polymerization, Xolography and holographic technologies promise the highest accuracy and dimensional freedom. But to transfer the light through the feedstock it needs sufficient transparency at the used light wavelength. Ceramic particles used for powder processing routes act as scattering sites and therefore hinder the light transmission, unless… The particle size and particle size distribution are chosen small and narrow enough. Particles which are smaller than roughly 1/10th of the light wavelength, mostly nanoparticles around 5nm size, decrease scattering vastly. This turns resins even with homogeneously distributed ceramic weight fraction of up to 80% transparent again. Feedstocks could be prepared for the highly accurate two-photon-polymerization gaining the smallest yttria stabilized zirconia structures with a resolution of 500nm and unique mechanical properties. The same feedstocks could be applied to DLP and LCM as layer-by-layer AM-technologies for bigger parts. Hybridizing both technologies lead to ceramic parts with microscopic accuracy at macroscopic dimensions. The feedstock was even applied to the volumetric Xolography with the highest transparency requirement so far and to versatile and flexible holographic AM. Highly filled nano-particle containing transparent ceramic feedstocks open the way for technical ceramics in high precision manufacturing where the performance and durability and accessibility are increased and created by the unique ceramic properties such as mechanical strength, chemical and thermal resistance and biocompatibility T2 - 14th International Conference on Ceramic Materials and Components for Energy and Environmental Systems CY - Budapest, Hungary DA - 18.08.2024 KW - Transparent KW - Ceramic KW - Additive manufacturing PY - 2024 AN - OPUS4-60891 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -