In selective laser melting (SLM) the variation of process parameters significantly impacts the resulting workpiece characteristics. In this study, AISI 316L was manufactured by SLM with varying laser power, layer thickness, and hatch spacing. Contrary to most studies, the input energy density was kept constant for all variations by adjusting the scanning speed. The varied parameters were evaluated at two different input energy densities. The investigations reveal that a constant energy density with varying laser parameters results into considerable differences of the workpieces' roughness, density, and microhardness. The density and the microhardness of the manufactured components can be improved by selecting appropriate parameters of the laser power, the layer thickness, and the hatch spacing. For this reason, the input energy density alone is no indicator for the resulting workpiece characteristics, but rather the ratio of scanning speed, layer thickness, or hatch spacing to laser power. Furthermore, it was found that the microhardness of an additively manufactured material correlates with its relative density. In the parameter study presented in this paper, relative densities of the additively manufactured workpieces of up to 99.9% were achieved.
The metastable austenitic stainless steel AISI 347 offers the possibility to induce a phase transformation from γ-austenite to ε- and α’-martensite when machining. This knowledge is well understood during cryogenic turning and was already applied to improve the surface morphology of metastable austenitic steel. However, the potential of this in-process hardening method is so far limited to rotationally symmetrical components. The aim of this study is to investigate deformation induced phase transformation during cryogenic milling, aiming at an improved surface morphology and at the resulting beneficial surface properties of the workpiece for parts with complex geometries.
Die Zerspanung von Ti-6Al-4V zeichnet sich durch hohe thermische Belastungen am Werkzeug aus. Dies führt zu einem ausgeprägten, thermisch induzierten Werkzeugverschleiß. Mithilfe einer kryogenen Kühlung können die thermische Belastung des Werkzeugs gesenkt und somit der thermisch bedingte Verschleiß erheblich reduziert werden. In diesem Beitrag wird gezeigt, dass eine kryogene Kühlung den thermisch induzierten Werkzeugverschleiß verringert und damit die Standwege der Werkzeuge verlängert werden können.
Das Hochgeschwindigkeits-Laserauftragschweißen (HLA) stellt einen innovativen Ansatz zur additiven Fertigung metallischer Werkstoffe dar. Durch deutlich erhöhte Auftragsraten im Vergleich zu herkömmlichen additiven Verfahren, wie etwa dem Pulverbettverfahren, wird die Produktivität gesteigert und somit ein wirtschaftlicher Einsatz der additiven Fertigung realisiert. Aufgrund des derzeit niedrigen Technologie-Reifegrads des HLA-Verfahrens gibt es jedoch noch wenig erprobte Werkstoffe. Der Edelstahl 17-4 PH stellt aufgrund seiner Kombination aus Korrosionsbeständigkeit, mechanischer Festigkeit und Härte einen industriell verbreiteten Werkstoff dar, für den in dieser Studie geeignete Parameter in Bezug auf das HLA-Verfahren ermittelt wurden.
The use of additive manufacturing (AM) in industrial applications is steadily increasing due to its near net shape production and high design-freedom. For metallic components, laser-based powder bed fusion (L-PBF) is currently one of the most widely used AM processes. During L-PBF, a component is manufactured layer by layer from a powdery raw material. The process is controlled by a multitude of parameters like the laser power, scanning speed and layer thickness, whose combination significantly influences the properties of the components.
In this study, the influence of the L-PBF machine type and the influence of the powder batch are investigated by means of relative density, microhardness and microstructure of the components. For this purpose, three setups are defined, differing in the powder batch and machine type used. By comparing the process results of the additive manufacturing of different setups, the influence of the machine type and powder batch are determined. The considered material is stainless steel AISI 316L. The results revealed significant differences between all investigated properties of the additively manufactured components. Consequently, process parameter combinations cannot be transferred between different machine types and powder batches without verification of the component properties and, if necessary, special adaption of the process.
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