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.
Due to an excellent ratio of high strength and low density, Ti-6Al-4V is suitable for many industrial applications, especially in the aerospace industry. However, Ti-6Al-4V is also characterized by a very low thermal conductivity and high chemical reactivity which is why the titanium alloy is considered to be a hard-to-cut material. Machining Ti-6Al-4V leads to high cutting temperatures, which leads to a rapidly progressing thermo-chemical induced tool wear. To reduce the thermal load and to enhance the cutting performance, suitable cooling strategies are a necessity. A novel, highly efficient cooling approach is to apply sub-zero metalworking fluids (MWF) at liquid state but at supply temperatures well below 0 °C. These sub-zero MWF inhibit high cooling effects due to their low supply temperature in superposition with a beneficial wetting behavior. In this work, the application of a sub-zero cooling strategy is investigated when milling Ti-6Al-4V. The influence of both down milling and up milling is investigated under a systematic variation of the cutting speed and feed per tooth. For comparison, the experiments are also conducted using a cryogenic CO2 cooling. The performance of both cooling strategies in dependence of the milling process is described on the basis of the occurring forces, the resulting tool wear, and the surface quality achieved. The results show that the sub-zero cooling can successfully improve the machinability of Ti-6Al-4V even at elevated cutting parameters and unfavorable cutting conditions. As a result, sub-zero milling clearly outperforms the cryogenic CO2 cooling, since less tool wear and an overall lower surface roughness are observed. Consequently, when using a sub-zero cooling strategy, higher metal removal rates, longer tool life, and better surface qualities are achievable.
Das Einsatzverhalten dünnwandiger, monolithischer Aluminiumlegierungen, welche in der Luft- und Raumfahrtindustrie eingesetzt werden, wird maßgeblich durch deren Oberflächenmorphologie beeinflusst. Diese setzt sich aus den mechanischen und metallurgischen Randschichteigenschaften sowie der Oberflächentopografie zusammen. In diesem Beitrag wird der Einfluss der Schnittparameter auf die Rauheit, die Mikrostruktur, die Mikrohärte sowie auf prozessinduzierte Eigenspannungen von gefrästem Al 7050 untersucht.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.