List of Abstracts 2024: SESSION C - ADDITIVE MANUFACTURING II

Additive manufacturing (AM) represents a promising technology in the nuclear power industry, offering unique capabilities for the fabrication of components for nuclear fuel elements. This study deals with the application and utilization of AM, particularly Laser Powder Bed Fusion (L-PBF) and Laser Directed Energy Deposition (L-DED), for production of nuclear reactor fuel components, with a specific emphasis on stainless steel 316L.
This study is mainly focused on the L-PBF method due to its precise control over material deposition and superior surface finish, which are imperative for fabricating components with strict nuclear safety standards. The use of L-PBF technology enables the production of complex structures such as debris filters, top and bottom nozzles, spacer grids and other FA elements, etc., with enhanced efficiency and reliability. The advantages of L-PBF over traditional manufacturing methods include reduced material waste, shorter lead times, and the ability to create complex geometries that are otherwise unattainable. Moreover, L-PBF allows direct production of components from digital designs, facilitating rapid prototyping and customization to specific reactor requirements.
In cooperation between ALVEL, a.s. and COMTES FHT a.s., the primary objective of the project is to utilize L-PBF technology and stainless steel 316L as a material of interest, to fabricate essential parts of reactor core components for VVER reactors. Extensive tests are being conducted to ensure the reliability of the manufacturing process. This includes optimizing printing parameters and post-processing procedures to achieve geometry compliance, as well as ensuring optimal material properties. Through rigorous testing and refinement, we aim to establish a robust and reliable manufacturing process that meets the safety and performance requirements of nuclear reactor core components.

Ti-Mo alloys are established materials for use in medical devices as they are among few Ti alloys having a biomedical certification. Additive manufacturing presents a ground-breaking technology which allows manufacturing parts with net-shape which saves costs with machining and can reduce material wastes. Additionally, when using a multi-hopper laser directed energy deposition, gradients in composition and thus also in microstructure / mechanical properties can be created by altering the feed rates of input powders. Pure Ti and Ti-15Mo alloy powders were used for deposition of samples with constant as well as graded Mo content. The variation of laser power, platform preheating and sample size were studied with the help of 1D FEM modelling and the knowledge of the occurring phase transformations helped with validation of thermal history predicted by the model. Microhardness, microstructure and phase composition of as-deposited gradient samples were subsequently studied while considering the modeled trends of thermal history. The most important parameter affecting the local phase composition in as-deposited condition is the layer position in the vertical direction with respect to the beta transus temperature and its last crossing during reheating when depositing subsequent layers. The rate of cooling after finishing the deposition influences mainly the last few deposited layers.

The development of advanced materials with gradual compositional changes is essential for applications requiring tailored properties. This study explores the fabrication of Functionally Graded Materials (FGMs) and Bimetallics using Directed Energy Deposition (DED) technology with two types of metal powders, C103(Nb based Alloy) and Ti-6Al-4V(Ti based Alloy). By systematically varying the composition across layers, FGM samples were produced, with material ratios changing by 10% per layer. Microstructural analysis using a Scanning Electron Microscope (SEM) confirmed successful FGM production without delamination or cracks. Energy Dispersive X-ray Spectroscopy (EDS) analysis revealed continuous compositional changes across 11 steps. And the rocket nozzle extension was manufactured using combination of two materials. This research demonstrates that DED-based FGM production using the C103 alloy has potential utility in aerospace product design and manufacturing. Future research will focus on a detailed analysis of the properties and optimization of the FGM production process.

Additive manufacturing (AM) methods are well suited to produce complex geometries, thus enabling design innovation in medical implants, novel internal cooling channels for high-efficiency engines, and lattice structures to reduce weight in aerospace industries. However, the inspection of these complex geometries, especially the internal structure, is challenging with traditional measurement systems. The inspection challenge extends beyond the simple dimensional measurement of hidden features to flaws and porosity that can arise during the printing process, microstructure change related to the choice of printing parameters, the roughness of surfaces, and even loose powder that could not be removed during AM post-processing cleanup. With recent advances in computed tomography (CT) detection hardware and the use of sources that operate at high X-ray energies, large and dense AM parts can be scanned non-destructively. This makes CT the method of choice for the inspection and measurement of AM products. This paper discusses modern X-ray CT and 3D X-ray microscopy (XRM) assisted with deep learning (DL) approaches that can be used for characterization of AM parts, not only to inspect the final product but also to evaluate the AM process during its different stages. Additionally, the use of DL techniques to increase measurement throughput and image quality improvement is demonstrated on some representative AM parts.

Additive manufacturing expands the creative scope for designers. However, in order to utilise the advantages of this technology for dynamically loaded components, experimental component strength tests are required. This is a major hurdle for small and medium-sized companies in particular. They would benefit significantly from methods for adequate service life estimation. In the study, both the static properties and the fatigue behaviour of samples additively manufactured from AlSi10Mg are determined, including a detailed investigation of the microstructures. In parallel, a novel proposal for estimating the fatigue behaviour is presented, which is based on the approaches of Luong and Risitano and is based on the phenomenon of self-heating. The simplicity and efficiency of this method provides a cost-efficient and time-saving way of determining the dynamic behaviour with fewer samples than is the case with conventional approaches.

Refractory high entropy alloys represent a promising group of materials for applications in fields requiring high-temperature strength and oxidation resistance. The fabrication of such alloys presents both a technological and economical challenge for conventional technologies. The additive manufacturing of high entropy alloys has recently gained broad attention from researchers. Most published articles are concerned with preparing HEAs composed mainly of 3d transition metals. Only a limited amount of work has been done on the additive manufacturing of refractory high entropy alloys. Additionally, the manufactured samples were prepared using complex procedures that do not highlight the main benefits of additive manufacturing and laser-based technologies. A quaternary refractory high entropy alloy based on the Cr-Nb-Ti-Zr system from an elemental powder blend was successfully prepared using commercially available L-DED apparatus. An optimized technological procedure was developed by a critical assessment of deposition parameters. Subsequent analysis of microstructure, phase, and chemical composition was conducted in an as-deposited state using scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. The alloys contain an Nb and Ti-rich bcc phase and a secondary phase with a Laves C15 structure. Furthermore, Vickers hardness testing shows an increasing trend with the rising amount of the strengthening Laves phase. Miniaturized tensile testing presents results of promising high-temperature strength but very limited room-temperature ductility.

Additive manufacturing processes, such as Laser Powder Bed Fusion (LPBF), open up new opportunities and possibilities for the production of complex and bionically optimized components. This manufacturing technology offers enormous potential for lightweight construction. To fully utilize this potential, an in-depth understanding of the material and failure behavior of additively manufactured materials is necessary. The failure and damage behavior of additively manufactured AlSi10Mg is already a central focus of research. However, the influence of stress states and the effects of process defects on failure behavior are not yet fully understood. Therefore, the aim of this study is to identify and describe the micromechanical processes involved in the failure of additively manufactured AlSi10Mg under quasi-static loading. Additionally, the influence of stress triaxiality on the material and failure behavior of this alloy will be addressed.

The general awareness of SIEMENS products includes the idea of a comprehensive platform for development, design, technology and production. We will introduce the software solution for the additive manufacturing sector and the demonstration will cover the pre-production phase, simulation phase and production phase of additive processes across a wide range of additive methods. The openness of the system is also a great advantage for R&D support, and thanks to the NX Open API, it allows to automate various design tasks, and solve technological problems in an interesting way.

The use of additive manufacturing technologies for the production of turbine components in the field of power generation has the potential to maintain the economic efficiency of gas and steam turbines, even under the increased demands on efficiency and flexibility resulting from the energy transition. For complex additively manufactured components and their reliable use, the existence of verified characteristic values and concepts for determining such characteristic values is of essential importance. It must be taken into account that additive manufacturing processes such as the LPBF process can produce a wide range of material properties due to the variety of process parameters, locally varying cooling conditions and geometric component characteristics.
In the research work presented here, a generic component was developed that can represent a real component in terms of the microstructures that occur. Samples were taken from this component at 0°, 45° and 90° to the build-up orientation. The results of the hot tensile tests and the creep tests are compared with the results obtained from printed samples. The test materials are IN718, IN738LC and X12CrMoWVNbN10-1-1. The investigations are accompanied by microstructural analyses. The result of this comparison for the nickel-based alloys is that the microstructural and mechanical properties of samples cannot be directly transferred to components due to different solidification conditions and the resulting differences in grain size, phase formation and different segregation behaviour. A small grain size causes a low creep life. For nickel-based alloys, the orientation to the build-up direction also has a considerable influence on the creep behaviour. The mechanisms of creep deformation depend strongly on the phase formation and the microstructure. The X12 test material shows no dependence of the microstructure on the orientation to the build-up direction due to the heat treatment carried out.

The study investigates the integration of microscopy and imaging techniques to explore the microstructural characteristics of a 316L stainless steel composite reinforced with tungsten carbide (WC), utilizing the Directed Energy Deposition (DED) method of additive manufacturing. In terms of methodology, the composite specimens of 316L + WC were fabricated from powder feedstock, focusing on controlling particle size and optimizing deposition parameters via Direct Metal Tooling (DMT). The research employed an array of sophisticated metallographic techniques, including light microscopy, electron microscopy, and confocal microscopy. These techniques were instrumental in analyzing the microstructure of the materials in their as - built and heat-treated states.
The results from the microscopic examinations proved an austenitic matrix of stainless steel with uniformly distributed WC particles. This specific microstructural formation significantly enhances the material's durability and overall performance, attributed mainly to the optimized additive manufacturing parameters that ensure uniform distribution of WC particles within the stainless steel matrix. The corrosion tests were integral in assessing the material's resistance to environmental degradation, particularly in corrosive environments, which is crucial for applications in industries like marine engineering and chemical processing. Conclusively, the study demonstrates that the strategic incorporation of WC particles into 316L stainless steel through additive manufacturing not only optimizes the material's structural integrity but also significantly boosts its performance in demanding tooling applications. This research highlights the crucial role of advanced microscopy in understanding and optimizing material properties, paving the way for further explorations into high-performance composite materials for various industrial applications.