The laser powder bed fusion (L-PBF) technology has been well recognized among the different manufacturing processes due to its remarkable ability to facilitate the production of light-weight metallic structures with minimal material wastes, highlighting the environmental benefits. However, the high cost of the products represents one of the main barriers that hinder the deployment of such technology in many industrial fields, especially for those relying on a mass-production scale. Hence, the L-PBF product-cost requires further optimization, which is suggested in this study by developing low-cost powders produced by water atomization process. This atomization technique has proven to be a cost-effective alternative to the standard gas atomization process, specifically for the production of large powder batches. Another aspect of this research is oriented towards the development of structural steels for L-PBF. Despite the widespread and predominant applications of advanced high strength steels for structural components, the processing of low-alloy steels by L-PBF has not yet reached the same degree of confidence achieved by conventional routes. Consequently, the library of approved Fe-based materials is still confined to stainless steels and maraging grades. Accordingly, this research focuses on the processing of several developed plain-carbon and low-alloy steels by L-PBF starting from water atomized feedstocks. In particular, the metallurgical features of 10 L-PBF structural steels based on different alloying systems were investigated by characterizing the microstructures and evaluating the mechanical properties. Moreover, post-process thermal treatment schedules were designed and applied according to thermodynamic simulations aiming to generate optimal microstructures for enhancing the mechanical behavior. The main findings of these studies promoted the water atomization process to be a potential alternative route for delivering sustainable feedstock materials for L-PBF. In addition, the combined cost-effective approaches of both the suggested powders and the developed steels could shift the potential from prototyping to affordable mass-production goods in favor of light-weight steel structures for the automotive applications.
Tra i diversi processi produttivi, la fusione laser a letto di polvere (L-PBF) è una tecnologia ampiamente riconosciuta grazie alla notevole capacità di facilitare la fase di progettazione e alla possibilità di ottenere strutture metalliche leggere con il minimo spreco di materiale, con conseguenti benefici ambientali. Tuttavia, il costo elevato dei prodotti L-PBF rimane l'ostacolo principale all'impiego di tale tecnologia in diversi campi industriali, specialmente per coloro che fanno affidamento su una scala di produzione di massa. L’ottimizzazione dei costi può essere raggiunta sviluppando un processo più economico di ottenimento della polvere utilizzata come materia prima per applicazioni L-PBF. Infatti, mentre le polveri standard sono prodotte tramite atomizzazione a gas, un approccio basato sull’atomizzazione ad acqua risulta più conveniente, specialmente per la produzione di grandi lotti. Nonostante le diffuse applicazioni di acciai avanzati ad alta resistenza per componenti strutturali, la lavorazione degli acciai basso legati prodotti tramite L-PBF non ha ancora raggiunto lo stesso grado di confidenza rispetto alle tecniche convenzionali. Di conseguenza, la lista dei materiali a base-Fe approvati è ancora limitata agli acciai inossidabili e maraginig. L’aspetto principale di tale ricerca è quindi basato sullo sviluppo e produzione tramite L-PBF di diversi acciai al carbonio e acciai bassolegati, entrambi prodotti a partire da polvere atomizzata ad acqua. In particolare, sono state studiate le caratteristiche metallurgiche di 10 acciai strutturali L-PBF basati su diversi sistemi di lega, caratterizzando le microstrutture e valutando le proprietà meccaniche. Inoltre, sono stati effettuati programmi di trattamento termico post-processo basati su simulazioni termodinamiche con l'obiettivo di generare microstrutture ottimali per migliorare il comportamento meccanico. I risultati principali di questi studi hanno promosso il processo di atomizzazione ad acqua come una potenziale via alternativa per ottenere materie prime sostenibili per L-PBF. Inoltre, gli approcci combinati economicamente vantaggiosi tra polveri suggerite e acciai sviluppati potrebbero spostare l’interesse dalla prototipazione alla produzione di massa con prezzi accessibili di strutture in acciaio leggero per le applicazioni automobilistiche.
Development and L-PBF processing of structural low-alloy steels for automotive applications
Abdelwahed, Marawan
2021/2022
Abstract
The laser powder bed fusion (L-PBF) technology has been well recognized among the different manufacturing processes due to its remarkable ability to facilitate the production of light-weight metallic structures with minimal material wastes, highlighting the environmental benefits. However, the high cost of the products represents one of the main barriers that hinder the deployment of such technology in many industrial fields, especially for those relying on a mass-production scale. Hence, the L-PBF product-cost requires further optimization, which is suggested in this study by developing low-cost powders produced by water atomization process. This atomization technique has proven to be a cost-effective alternative to the standard gas atomization process, specifically for the production of large powder batches. Another aspect of this research is oriented towards the development of structural steels for L-PBF. Despite the widespread and predominant applications of advanced high strength steels for structural components, the processing of low-alloy steels by L-PBF has not yet reached the same degree of confidence achieved by conventional routes. Consequently, the library of approved Fe-based materials is still confined to stainless steels and maraging grades. Accordingly, this research focuses on the processing of several developed plain-carbon and low-alloy steels by L-PBF starting from water atomized feedstocks. In particular, the metallurgical features of 10 L-PBF structural steels based on different alloying systems were investigated by characterizing the microstructures and evaluating the mechanical properties. Moreover, post-process thermal treatment schedules were designed and applied according to thermodynamic simulations aiming to generate optimal microstructures for enhancing the mechanical behavior. The main findings of these studies promoted the water atomization process to be a potential alternative route for delivering sustainable feedstock materials for L-PBF. In addition, the combined cost-effective approaches of both the suggested powders and the developed steels could shift the potential from prototyping to affordable mass-production goods in favor of light-weight steel structures for the automotive applications.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/183138