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1Graduate School of Engineering, Osaka University, 1-1 Yamadaoka, Suita, Osaka, 565-0871, Japan; 2Graduate School of Science and Engineering, Kindai University, 3-4-1 Kowakae, Higasiosaka, Osaka, 577-8502, Japan; 3Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka, 567-0047, Japan
Selective laser melting (SLM), which is an additive manufacturing technology, is a method that metal powder was melted and solidified by laser. There was a problem that distribution of crystal grain size was caused inhomogeneous by excessive input because of laser irradiation layer by layer. It was thought that anisotropy could be eliminated by controlling grain growth through precise control of heat input. In order to control a heat input, modulated pulses for laser were used. Purpose in this study, Ti64, which is clinical applied as an implant material due to its biocompatibility as well as its high corrosion and mechanical resistance, was fabricated with modulation pulses of laser. As the results, it was found that the pulse energy increase with increase the grain size of Ti64 plate fabrication.
10:15am - 10:30am
Development of a machine concept for the processing of Ti6Al4V in the LPBF process under silandized argon atmosphere
Marijan Tegtmeier, Nicole Emminghaus, Jannes August, Marius Lammers, Christian Hoff, Jörg Hermsdorf, Ludger Overmeyer, Stefan Kaierle
Laser Zenrum Hannover e.V., Germany
The presence of oxygen in the LPBF process leads to embrittlement in the workpiece in materials with high affinity to oxygen. Especially the metal powder Ti6Al4V requires a special protective atmosphere during processing. By doping the argon 1.5% with monosilane, the residual oxygen of a usual argon atmosphere is bound and reduced to a value typical for XHV (Extreme High Vacuum).
Basically, the development of an LPBF system according to VDI 2221 is presented. The admixture of silane requires an innovative machine concept in order to ensure the compatibility of the materials used and to prevent the process gases from becoming hazardous. The phases of development are accompanied by comprehensive reaction studies and flow simulations. The resulting concept relies on a compact machining area (Ø100x100mm) and breaks new ground in the processing of special materials, not only through the process gases used, but also in powder and workpiece management.
10:30am - 10:45am
Influence of laser focus shift on porosity and surface quality of additively manufactured Ti-6Al-4V
Nicole Emminghaus, Christian Hoff, Jörg Hermsdorf, Stefan Kaierle
Laser Zentrum Hannover e.V., Germany
In laser-based powder bed fusion of metals (PBF-LB/M) an increase of the laser spot size by shifting the focus position offers the opportunity of reducing the overall scanning time as well as achieving a more stable melt pool behavior. However, the influence on porosity and surface roughness of bulk samples has received little attention so far. In this work, the influence of laser focus shift (Yb-fiberlaser, minimum beam diameter of 35 µm) on part porosity as well as top and side surface roughness is investigated for additively manufactured Ti-6Al-4V. The focusing lens position relative to its standard setting is varied between 1.2 mm and -8.7 mm and the resulting track width is evaluated. Further, the main processing parameters are varied. The influences and interaction effects of all varied parameters are statistically evaluated according to the design of experiments approach. Optimum settings for low porosity and surface roughness are presented.