Among the additive manufacturing techniques, Direct Energy Deposition (DED), is widely used to fabricate complex three-dimensional metallic components using a layer by layer approach. The major drawback of components manufactured using this technique is the surface quality, which is generally beyond the acceptable range. Therefore, there is a need for hybrid manufacturing, including additive manufacturing and finish machining processes to be developed and implemented in the industry. In my study a complete process chain from fabrication, heat treatment to finish machining operation of additive manufactured DED 316 L stainless steel tubes has been studied. A qualitative analysis which involves the measurement of dimensional characteristics of the tubes in terms of diameter, roundness, cylindricity; the roughness measurement of the tubes and the determination of micro hardness of additive manufactured DED 316 L tubes has been carried out at each of the following step: as built, heat treated and after machining. The experimental study reveals that the DED 316 L tubes produced were not perfect cylinders and there was some conicity in the tubes. Moreover, heat treatment had a positive impact on the dimensional and surface characteristics of the DED 316 L tubes since both the roundness and surface roughness of DED 316 L tubes reduced. The surface roughness and micro hardness at position close to the substrate was found to be significantly different from the roughness and to the micro hardness values at the middle and close to the edge of additive manufactured DED 316 L stainless steel tubes. The experimental study reveals that finish machining resulted in a lower surface roughness and increased micro hardness of additive manufactured DED 316 L stainless steel cylindrical tubes. A design of analysis experiment was conducted to determine the effect of machining parameters such as cutting speed and feed rate on the surface roughness and micro hardness of additive manufactured DED 316 L stainless steel cylindrical tube. It was found out that feed rate had a major influence on the surface roughness and micro hardness of DED 316 L stainless steel tubes. The experimental results suggested that high cutting speed and feed rate results in poor surface finish and increased micro hardness of additive manufactured DED 316 L stainless steel tubes.
Tra le tecniche di produzione additiva, Direct Energy Deposition (DED), è ampiamente utilizzato per fabbricare complessi componenti metallici tridimensionali usando un approccio strato per strato. Il principale inconveniente dei componenti fabbricati usando questa tecnica è la qualità della superficie, che è generalmente oltre l'intervallo accettabile. Pertanto, vi è la necessità di una produzione ibrida, compresi i processi di produzione additiva e di finitura, da sviluppare e implementare nel settore. Nel mio studio è stata studiata una catena di processo completa dalla fabbricazione, trattamento termico per finire la lavorazione di tubi in acciaio inossidabile DED 316 L additivi prodotti. Un'analisi qualitativa che prevede la misurazione delle caratteristiche dimensionali dei tubi in termini di diametro, rotondità, cilindricità; la misurazione della rugosità dei tubi e la determinazione della microdurezza delle provette DED 316 L additive sono state eseguite in ciascuna delle seguenti fasi: come costruito, sottoposto a trattamento termico e dopo la lavorazione. Lo studio sperimentale rivela che i tubi DED 316 L prodotti non erano cilindri perfetti e c'era una certa conicità nei tubi. Inoltre, il trattamento termico ha avuto un impatto positivo sulle caratteristiche dimensionali e superficiali dei tubi DED 316 L poiché sia la rotondità che la rugosità superficiale dei tubi DED 316 L sono stati ridotti. La rugosità superficiale e la microdurezza in posizione vicino al substrato sono risultate significativamente diverse dalla rugosità e ai valori di micro durezza al centro e vicino al bordo dei tubi di acciaio inossidabile DED 316 L additivi fabbricati. Lo studio sperimentale rivela che la lavorazione delle finiture ha prodotto una minore rugosità superficiale e una maggiore durezza micro dei tubi cilindrici in acciaio inossidabile DED 316 L additivi prodotti. È stato condotto un progetto di esperimento di analisi per determinare l'effetto di parametri di lavorazione quali velocità di taglio e velocità di avanzamento sulla rugosità superficiale e micro durezza del tubo cilindrico in acciaio inossidabile DED 316 L additivo fabbricato. È stato scoperto che la velocità di alimentazione ha avuto un'influenza maggiore sulla rugosità superficiale e sulla microdurezza dei tubi in acciaio inossidabile DED 316 L. I risultati sperimentali hanno suggerito che un'elevata velocità di taglio e velocità di avanzamento si traducono in una scarsa finitura superficiale e una maggiore durezza micro dei tubi in acciaio inossidabile DED 316 L additivi prodotti.
Study of a process chain for additive manufactured AISI 316L stainless steel tubes
HAIDER, ALI
2018/2019
Abstract
Among the additive manufacturing techniques, Direct Energy Deposition (DED), is widely used to fabricate complex three-dimensional metallic components using a layer by layer approach. The major drawback of components manufactured using this technique is the surface quality, which is generally beyond the acceptable range. Therefore, there is a need for hybrid manufacturing, including additive manufacturing and finish machining processes to be developed and implemented in the industry. In my study a complete process chain from fabrication, heat treatment to finish machining operation of additive manufactured DED 316 L stainless steel tubes has been studied. A qualitative analysis which involves the measurement of dimensional characteristics of the tubes in terms of diameter, roundness, cylindricity; the roughness measurement of the tubes and the determination of micro hardness of additive manufactured DED 316 L tubes has been carried out at each of the following step: as built, heat treated and after machining. The experimental study reveals that the DED 316 L tubes produced were not perfect cylinders and there was some conicity in the tubes. Moreover, heat treatment had a positive impact on the dimensional and surface characteristics of the DED 316 L tubes since both the roundness and surface roughness of DED 316 L tubes reduced. The surface roughness and micro hardness at position close to the substrate was found to be significantly different from the roughness and to the micro hardness values at the middle and close to the edge of additive manufactured DED 316 L stainless steel tubes. The experimental study reveals that finish machining resulted in a lower surface roughness and increased micro hardness of additive manufactured DED 316 L stainless steel cylindrical tubes. A design of analysis experiment was conducted to determine the effect of machining parameters such as cutting speed and feed rate on the surface roughness and micro hardness of additive manufactured DED 316 L stainless steel cylindrical tube. It was found out that feed rate had a major influence on the surface roughness and micro hardness of DED 316 L stainless steel tubes. The experimental results suggested that high cutting speed and feed rate results in poor surface finish and increased micro hardness of additive manufactured DED 316 L stainless steel tubes.| File | Dimensione | Formato | |
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Descrizione: THESIS REPORT " Study of a Process chain for Additive Manufactured AISI 316 L stainless steel tubes"
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https://hdl.handle.net/10589/146156