Local and systemic inflammation after implantation of a novel iron based porous degradable bone replacement material in sheep model

Despite the high potential of healthy bone to regenerate, the reconstruction of large bone defects remains a challenge. Due to the lack of mechanical stability of existing bone substitutes, recently developed degradable metallic alloys are an interesting alternative providing higher load-bearing capabilities. Degradable iron-based alloys therefore might be an attractive innovation. To test the suitability of a newly-designed iron-based alloy for such applications, an animal experiment was performed. Porous iron-based degradable implants with two different densities and a control group were tested. The implants were positioned in the proximal tibia of Merino sheep. Over a period of 6 and 12~months, blood and histological parameters were monitored for signs of inflammation and degradation. In the histological evaluation of the implants` environment we found degraded alloy particles, but no inflammatory reaction. Iron particles were also found within the popliteal lymph nodes on both sides. The serum blood levels of phosphorus, iron and ferritin in the long term groups were elevated. Other parameters did not show any changes. Iron-based degradable porous bone replacement implants showed a good biocompatibility in this experiment. For a clinical application, however, the rate of degradation would have to be significantly increased. Biocompatibility would then have to be re-evaluated

Verfahren zur Herstellung eines Werkstoffverbundes, einen Werkstoffverbund sowie eine Verwendung des Werkstoffverbundes als Wärmeleiter sowie -überträger

The invention relates to a process for producing a material composite (200) comprising the steps: producing (S100) a composite material (20) that extends along an axis of elongation (z), composed of carbon nanostructures anchored in a matrix of a first metal (24), preferably carbon nanostructures (22) wherein the carbon nanostructures (22) extend along the axis of elongation (z) of the composite material (20); subdividing (S200) the composite material (20) into segments (30) of the composite material (20); arranging (S400) the segments (30) in a plane of a die (100); filling (S500) cavities in the die (120) with a filler material (130); sintering (S600) in the die (100) to form a material composite (200), and exposing the carbon nanostructures (22) of the composite material (20) on at least one surface of the composite material (200), so that the carbon nanostructures (22) project from this surface. Also proposed are a material composite and the use thereof as a heat conductor and/or heat exchanger

Verfahren zum Herstellen dreidimensionaler Bauteile (DE102021211370A1)

Die vorliegende Erfindung betrifft ein Verfahren zum Herstellen dreidimensionaler Bauteile, bei dem aus einem pulverförmigen Ausgangswerkstoff (1), der mit mindestens zwei Komponenten gebildet ist, wobei die Komponenten einen unterschiedlichen Dampfdruck bei gleicher Temperatur aufweisen, durch ein additives Strahlfertigungsverfahren ein Bauteil hergestellt wird. Mindestens ein Prozessparameter zum Betrieb mindestens eines zweidimensional auslenkbaren Energiestrahls wird derart eingestellt, dass sich der Dampfdruck mindestens einer der Komponenten ändert, so dass der Anteil dieses chemischen Elements oder dieser Legierung im Bauteilvolumen lokal definiert im Bauteil variiert wird

Oxidation and Hot Gas Corrosion of Al–Cr–Fe–Ni-Based High-Entropy Alloys with Addition of Co and Mo

Multicomponent, high-entropy alloys (HEAs) are promising candidates for replacing conventional alloys in high-temperature applications. Herein, the high-temperature corrosion of AlCrFeNiX0.5 (X = Co, Mo) is investigated. The samples are tested for their oxidation resistance at temperatures up to 1200 °C for 120 h and their behavior in NaCl/Na2SO4 at 900 °C for 96 h. They are benchmarked against commercial alloys such as FeCrAl. Despite the same contents of Al and Cr, the HEAs form different oxide layers showing very different oxidation resistance. The type of oxide is related to the multiphase microstructure. The samples exhibit different amounts of ordered and unordered body-centered cubic (bcc) phase. The Co-containing specimen shows an oxidation resistance that performs similarly well as FeCrAl. Its behavior is ascribed to the formation of an Al2O3 layer, which is very stable at high temperatures. The sample with X = Mo exhibits an additional Mo-rich sigma phase, thus posing the risk of catastrophic oxidation. However, the Mo-containing HEA is more resistant in the environment of molten salt. Preoxidation treatment at a lower oxygen partial pressure proves to prolong life span of the Mo-containing HEA in hot air. Furthermore, a positive impact on oxidation resistance by addition of Y is affirmed. © 2021 The Authors. Advanced Engineering Materials published by Wiley-VCH GmbH

Gas Analysis and Optimization of Debinding and Sintering Processes for Metallic Binder-Based AM*

Binder-based additive manufacturing processes for metallic AM components in a wide range of applications usually use organic binders and process-related additives that must be thermally removed before sintering. Debinding processes are typically parameterized empirically and thus far from the optimum. Since debinding based on thermal decomposition processes of organic components and the subsequent thermochemical reactions between process atmosphere and metal powder materials make uncomplicated parameterization difficult, in-situ instrumentation was introduced at Fraunhofer IFAM. This measurement method relies on infrared spectroscopy and mass spectrometry in various furnace concepts to understand the gas processes of decomposition of organic components and the subsequent thermochemical reactions between the carrier gas atmosphere and the metal part, as well as their kinetics. This method enables an efficient optimization of the temperature-time profiles and the required atmosphere composition to realize dense AM components with low contamination. In the paper, the optimization strategy is presented, and the achievable properties are illustrated using a fused filament fabrication (FFF) component example made of 316L stainless steel.Bindemittelbasierte additive Fertigungsverfahren für metallische AM-Bauteile in einer Vielzahl von Anwendungen verwenden in der Regel organische Bindemittel und prozessbedingte Additive, die vor dem Sintern thermisch entfernt werden müssen. Die Entbinderungsprozesse sind typischerweise empirisch parametrisiert und damit weit vom Optimum entfernt. Da Entbinderungsprozesse, die auf thermischen Zersetzungsprozessen organischer Komponenten und den anschließenden thermochemischen Reaktionen zwischen Prozessatmosphäre und metallischen Pulverwerkstoffen beruhen, eine unkomplizierte Parametrierung erschweren, wurde am Fraunhofer IFAM eine in-situ-Messtechnik eingeführt. Diese Messmethode stützt sich auf Infrarotspektroskopie und Massenspektrometrie in verschiedenen Ofenkonzepten, um die gasförmigen Zersetzungsprozesse der organischen Komponenten und die nachfolgenden thermochemischen Reaktionen zwischen Schutzgasatmosphäre und Metallteil sowie deren Kinetik zu verstehen. Diese Methode ermöglicht eine effiziente Optimierung der Temperatur-Zeit-Profile und der erforderlichen Atmosphärenzusammensetzung, um dichte AM-Bauteile mit geringer Kontamination zu realisieren. In dem Beitrag wird die Optimierungsstrategie vorgestellt und die erreichbaren Eigenschaften werden am Beispiel eines Fused Filament Fabrication (FFF)-Bauteils aus Edelstahl 316L illustriert

PBF-EB of Fe-Cr-V Alloy for Wear Applications

Due to the small variety of materials, the areas of application of additive manufacturing in the toolmaking industry are currently still limited. In order to overcome these material restrictions, AM material development for high carbon-containing iron-based materials, which are characterized by high strength, hardness, and wear resistance, must be intensified. However, these materials are often susceptible to crack formation or lack of fusion defects during processing. Therefore, these materials are preferentially suited for electron beam powder bed fusion (PBF-EB). In this paper, an Fe-Cr-V alloy with 10% vanadium is presented. Investigations were carried out on the PBF-EB system Arcam A2X. Specimens and demonstrators are characterized by a three-phase microstructure with an Fe-rich matrix and VC and M7C3 reinforcements. The resulting microstructures were characterized by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Furthermore, mechanical and physical properties were measured. A final field test was conducted to evaluate durability in use

Electron Beam Powder Bed Fusion of Water Atomized Iron and Powder Blends

In the present state of the art, highly spherical alloy powders are employed as feedstock in powder bed fusion processes. These powders are characterized by high flowability and apparent density. Their elaborate fabrication process is reflected in high powder price, adding a significant fraction to the cost of additively manufactured parts. Thus, the use of non-spherical powders, such as water atomized material, can lower costs significantly. Here, the electron beam powder bed fusion (PBF-EB) of standard water atomized iron powder used for press-and-sinter is studied. Despite raking problems, using the coating mechanism in standard configuration samples with densities exceeding 99% were fabricated. In a further step, the addition of alloying elements by powder blending is explored. Important powder properties of feedstock blended from irregular and spherical powders are characterized. The PBF-EB processing of two alloys is presented. The first represents a low carbon steel. Samples were characterized by metallographic cross-section, energy dispersive X-ray (EDX) mapping, and mechanical testing. The second alloy system is a FeCrAl. After PBF-EB processing of the powder mixture, chemical homogeneity was achieved. Besides the low cost, this approach of using water atomized powder mixed with master alloy offers the advantage of high flexibility for potential application

Verfahren zum Glätten eines Bauteiloberflächenbereichs

The invention relates to a method for smoothing a surface region of a component (11; 21), which at least within the surface region consists of an electrically conductive material, wherein the surface region of the component (11; 21) is coated inside a vacuum chamber, by means of at least one focused electron beam (13; 23) with a first surface energy, which brings about melting of the component material within the surface region, wherein a), before melting, the surface region is passed over at least twice by the electron beam (13; 23), each time with a different focal length (27a; 27b; 27c) of the electron beam (13; 23), wherein b) a second surface energy is set for the electron beam (13, 23), such that no melting of the component material is brought about in the surface region, wherein c) data which characterize the electric current caused by the backscattered electrodes impinging on the sensors (14; 24) are recorded by means of a number of sensors (14; 24) arranged inside the vacuum chamber, wherein d) within an evaluation device (15; 25), an actual value for the roughness within the surface region is derived from the data recorded by the sensors (14; 24), the actual value of the roughness is compared with a setpoint value of the roughness and, if the actual value of the roughness has not reached the setpoint value of the roughness, a value for the first surface energy is determined in dependence on the result of the comparison, after which e) the surface region is passed over by the electron beam (13; 23) with the first surface energy, after which the procedure is continued with method step a)