In recent years, the increasing demand for advanced accelerator components with complex, compact design and the ability to sustain high-power operation has driven interest in additive manufacturing within the field of particle accelerators. Among the metallic materials typically employed in these applications, pure copper has received considerable attention due to its excellent electrical and thermal properties, crucial for components such as radio-frequency cavities, quadrupoles, waveguides, and klystrons. Copper-steel multimaterials, which combine the superior electrical and thermal conductivity of copper with the mechanical strength of steel, have also been proposed for manufacturing accelerator components exposed to severe thermomechanical conditions during operation. The primary challenges to the integration of additive manufacturing processes into the production workflows of copper and copper-steel accelerator components are related to the lack of standardized qualification protocols and the uncertainties regarding the performance and reliability of additively manufactured parts under the demanding operating conditions typical of accelerator applications. Another obstacle lies in the difficulty of predicting the quality of printed parts, which is influenced by numerous factors, including fabrication parameters and post-processing treatments. The aim of this thesis was to evaluate different additive manufacturing processes for the fabrication of copper and copper-steel accelerator components, with a main focus on material-related aspects, including chemical purity, microstructural integrity, and mechanical and physical properties, which are critical for the initial assessment of these technologies for particle accelerator applications. Among the various additive manufacturing techniques, laser powder bed fusion and binder jetting were investigated for processing pure copper, while laser directed energy deposition was explored for developing a practical workflow aimed at the fabrication of copper-steel multimaterial structures based on the study of the microstructural and thermophysical compatibility of the constituent materials. The experimental activities involved comprehensive testing of samples produced with the different additive manufacturing technologies, with the aim of identifying process limitations, critical challenges, and opportunities for improvement to meet the stringent material requirements of accelerator applications. Laser powder bed fusion demonstrated the capability of fabricating copper parts with density, purity level, electrical conductivity, and thermal diffusivity in line with pure copper standards. On the other hand, binder jetting experiments evidenced significant challenges in achieving high-quality parts due to the extensive presence of residual porosity and carbon impurities. Investigations into laser directed energy deposition confirmed the feasibility of producing copper-steel multimaterial components with a good combination of thermal properties and mechanical strength, although precise control over local chemical compositions was found to be essential to prevent the formation of regions prone to solidification cracking and ensure the structural integrity of the fabricated parts. These findings provide a basis for assessing the suitability of additive manufacturing technologies for the fabrication of copper-based components intended for particle accelerator applications, as well as guidance on the essential aspects to consider for their qualification.
Negli ultimi anni, la crescente domanda di componenti per acceleratori avanzati, complessi, compatti e in grado di operare a potenze elevate, ha acceso l’interesse per la manifattura additiva nel settore degli acceleratori di particelle. Tra i materiali metallici tipicamente impiegati in queste applicazioni, il rame puro ha ricevuto particolare attenzione per via delle sue eccellenti proprietà elettriche e termiche, cruciali per componenti a radio-frequenza come cavità acceleratrici, quadrupoli, guide d’onda e klystron. Anche i multimateriali rame-acciaio, che coniugano la conducibilità elettrica e termica del rame con la resistenza meccanica dell’acciaio, sono stati proposti per realizzare componenti per acceleratori sottoposti a condizioni termomeccaniche severe durante il funzionamento. Gli ostacoli principali all’integrazione dei processi di manifattura additiva nella produzione di componenti per acceleratori di rame puro e multimateriale rame-acciaio riguardano la mancanza di protocolli di qualificazione standardizzati e le incertezze sulle prestazioni e l’affidabilità dei pezzi fabbricati additivamente nelle ostiche condizioni operative tipiche degli acceleratori. Un’ulteriore sfida tecnica risiede nella difficoltà di prevedere la qualità dei pezzi stampati, che è influenzata da numerosi fattori, fra cui i parametri di fabbricazione e i trattamenti di post-processo. L’obiettivo di questa tesi è stato quello di valutare diversi processi di manifattura additiva per la realizzazione di componenti per acceleratori in rame puro e multimateriale rame-acciaio, con particolare attenzione agli aspetti legati al materiale, quali purezza chimica, integrità microstruttura e proprietà meccaniche e fisiche, cruciali per una valutazione iniziale di queste tecnologie nel settore degli acceleratori di particelle. Tra le varie tecniche di manifattura additiva, sono state studiate la fusione a letto di polvere (laser powder bed fusion, LPBF) e la stampa a getto di legante (binder jetting) per la stampa del rame puro, mentre la deposizione diretta di energia laser (laser directed energy deposition, LDED) è stata esplorata per sviluppare un iter di processo funzionale alla fabbricazione di strutture multimateriale rame-acciaio basato sullo studio della compatibilità microstrutturale e termofisica dei materiali costituenti. Le attività sperimentali hanno compreso test completi su campioni prodotti con le diverse tecnologie additive, con l’obiettivo di individuare i limiti di processo, gli aspetti critici e le opportunità di miglioramento per soddisfare i rigorosi requisiti sui materiali per applicazioni negli acceleratori. La fusione a letto di polvere ha dimostrato la capacità di fabbricare pezzi di rame con densità, livello di purezza, conducibilità elettrica e diffusività termica conformi agli standard del rame puro. Al contrario, gli esperimenti sulla stampa a getto di legante hanno evidenziato notevoli difficoltà nell’ottenere pezzi di buona qualità a causa della presenza estesa di porosità residua e impurità di carbonio. Lo studio sulla deposizione diretta di energia laser ha confermato la capacità di produrre componenti multimateriale rame-acciaio che mostrano una buona combinazione di conducibilità termica e resistenza meccanica, sebbene i risultati abbiano indicato che un controllo preciso della composizione chimica locale è essenziale per evitare la formazione di zone soggette a criccatura da solidificazione e garantire l’integrità strutturale dei pezzi. Questi risultati forniscono una base per valutare l’idoneità delle tecnologie di manifattura additiva per la produzione di componenti a base di rame destinati ad applicazioni negli acceleratori di particelle, evidenziando inoltre gli aspetti chiave da considerare per la loro qualificazione.
Additive manufacturing of pure copper and copper-steel multimaterials: investigation of material properties and insights into particle accelerator applications
Romano, Tobia
2025/2026
Abstract
In recent years, the increasing demand for advanced accelerator components with complex, compact design and the ability to sustain high-power operation has driven interest in additive manufacturing within the field of particle accelerators. Among the metallic materials typically employed in these applications, pure copper has received considerable attention due to its excellent electrical and thermal properties, crucial for components such as radio-frequency cavities, quadrupoles, waveguides, and klystrons. Copper-steel multimaterials, which combine the superior electrical and thermal conductivity of copper with the mechanical strength of steel, have also been proposed for manufacturing accelerator components exposed to severe thermomechanical conditions during operation. The primary challenges to the integration of additive manufacturing processes into the production workflows of copper and copper-steel accelerator components are related to the lack of standardized qualification protocols and the uncertainties regarding the performance and reliability of additively manufactured parts under the demanding operating conditions typical of accelerator applications. Another obstacle lies in the difficulty of predicting the quality of printed parts, which is influenced by numerous factors, including fabrication parameters and post-processing treatments. The aim of this thesis was to evaluate different additive manufacturing processes for the fabrication of copper and copper-steel accelerator components, with a main focus on material-related aspects, including chemical purity, microstructural integrity, and mechanical and physical properties, which are critical for the initial assessment of these technologies for particle accelerator applications. Among the various additive manufacturing techniques, laser powder bed fusion and binder jetting were investigated for processing pure copper, while laser directed energy deposition was explored for developing a practical workflow aimed at the fabrication of copper-steel multimaterial structures based on the study of the microstructural and thermophysical compatibility of the constituent materials. The experimental activities involved comprehensive testing of samples produced with the different additive manufacturing technologies, with the aim of identifying process limitations, critical challenges, and opportunities for improvement to meet the stringent material requirements of accelerator applications. Laser powder bed fusion demonstrated the capability of fabricating copper parts with density, purity level, electrical conductivity, and thermal diffusivity in line with pure copper standards. On the other hand, binder jetting experiments evidenced significant challenges in achieving high-quality parts due to the extensive presence of residual porosity and carbon impurities. Investigations into laser directed energy deposition confirmed the feasibility of producing copper-steel multimaterial components with a good combination of thermal properties and mechanical strength, although precise control over local chemical compositions was found to be essential to prevent the formation of regions prone to solidification cracking and ensure the structural integrity of the fabricated parts. These findings provide a basis for assessing the suitability of additive manufacturing technologies for the fabrication of copper-based components intended for particle accelerator applications, as well as guidance on the essential aspects to consider for their qualification.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/248297