Deposition Strategies for New Applications of Cold Spray Additive Manufacturing
[eng] The potential of CSAM has attracted the attention from the scientific community due to its advantages over other heat-focused AM methods, such as solid-state deposition, high deposition rates, ability to deposit temperature-sensitive materials, and reduction of tensile residual stresses, among...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2025 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/217918 |
| Acceso en línea: | https://hdl.handle.net/2445/217918 http://hdl.handle.net/10803/693426 |
| Access Level: | acceso abierto |
| Palabra clave: | Resistència de materials Metalls Strength of materials Metals |
| Sumario: | [eng] The potential of CSAM has attracted the attention from the scientific community due to its advantages over other heat-focused AM methods, such as solid-state deposition, high deposition rates, ability to deposit temperature-sensitive materials, and reduction of tensile residual stresses, among others. Therefore, the efforts of the researchers in the CSAM field are focused on developing this technology beyond its inherent challenges. To do so, state-of-the-art deposition strategies are currently being investigated. These new deposition strategies include optimizing the robotic path trajectories or employing masks to overcome constraints to manufacture objects with a more complex shape; introducing advanced strategies during spraying or process modifications, such as substrate preheating; and implementing post-process methods such as heat treatments or machining that help to enhance microstructure densification and surface finish, respectively. This thesis focuses on the development of CSAM as a metal AM technology by understanding the CSAM process variables and deposition strategies for its further development and application as an additive manufacturing technology. Two robot path trajectories, a traditional (T) toolpath, and a novel strategy called Metal Knitting (MK), were used for the reconstruction of CSAM parts from various metallic materials: Cu, Al, Ti, and Ti6Al4V. The final geometry, microstructure, and mechanical properties of the obtained parts were assessed and compared. It was found that the novel MK robot path trajectory enabled a precise control over the geometry of the reconstructed parts. However, the deposition angle reduced the plastic deformation of the particles, increasing porosity within the microstructure and hindering adhesion with the substrate. To address this, the effects of annealing on the components’ microstructure and its influence on adhesion, resistance to erosion, and abrasive wear were also evaluated. In this sense annealing was found to be an effective deposition strategy for reducing porosity, and improving cohesion between particles and adhesion with the substrate. It was concluded that spraying with the MK toolpath, followed by annealing, enabled the reconstruction of Cu and Al parts with iv mechanical properties comparable to other bulk production methods. Nevertheless, alternative deposition strategies are needed for the CSAM reconstruction of dense parts from less ductile materials such as Ti and Ti6Al4V. Moreover, the effects of substrate preheating on high-strength materials with low particle plasticity was investigated. Since the interest in repairing IN718 damaged parts with CSAM has increased in the last years, the effect of IN718 substrate preheating on the CSAM IN718 deposit microstructure and thickness, as well as the adhesion mechanisms and strength at room and preheating temperatures of 250 C and 400 ºC was evaluated. The results showed that the substrate preheating improved the bonding strength, adhesion, and cohesion of CS IN718 deposits by softening the substrate, which improved the materials’ plasticity during deposition. It was concluded that increasing the preheating temperature and the deposit thickness improved the deposit density, reaching values comparable to an IN718 bulk reference, > 99.9%. Finally, the fabrication of 3D patterned parts with a desired pattern based on a bottom-up approach using a masked CSAM deposition strategy was investigated for fabricating new Ti bipolar plates (BPPs) for Proton Exchange Membrane (PEM) electrolyzers. The dimensional and microstructural characteristics of pin fins fabricated with spherical and irregular Ti powders were assessed. The results demonstrated that the masked CSAM technology allowed precise control and customization of the dimensions of the 3D-printed pin fins. Additionally, the performance of both Ti parts for its application in PEM electrolyzers was evaluated in terms of corrosion resistance and interfacial contact resistance (ICR). The results suggest than the masked CSAM technology shows great potential for the fabrication of Ti BPPs |
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