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Material characterization of AISI 316L flexure pivot bearings fabricated by additive manufacturing

: Riede, Mirko; Knoll, Matthias; Wilsnack, Christoph; Gruber, Samira; Cubillo, Alba Alegre; Melzer, Christian; Brandao, A.D.; Pambaguian, Laurent; Seidel, André; López, Elena M.; Brückner, Frank; Leyens, Christoph

Fulltext ()

Materials 12 (2019), No.15, Art. 2426, 24 pp.
ISSN: 1996-1944
Journal Article, Electronic Publication
Fraunhofer IWS ()
additive manufacturing; laser metal deposition; flexure pivot; space application

Recently, additive manufacturing (AM) by laser metal deposition (LMD) has become a key technology for fabricating highly complex parts without any support structures. Compared to the well-known powder bed fusion process, LMD enhances manufacturing possibilities to overcome AM-specific challenges such as process inherent porosity, minor build rates, and limited part size. Moreover, the advantages aforementioned combined with conventional machining enable novel manufacturing approaches in various fields of applications. Within this contribution, the additive manufacturing of filigree flexure pivots using 316L-Si by means of LMD with powder is presented. Frictionless flexure pivot bearings are used in space mechanisms that require high reliability, accuracy, and technical cleanliness. As a contribution to part qualification, the manufacturing process, powder material, and fabricated specimens were investigated in a comprehensive manner. Due to its major impact on the process, the chemical powder composition was characterized in detail by energy dispersive X-ray spectroscopy (EDX) and inductively coupled plasma optical emission spectrometry (ICP-OES). Moreover, a profound characterization of the powder morphology and flowability was carried out using scanning electron microscopy (SEM) and novel rheological investigation techniques. Furthermore, quantitative image analysis, mechanical testing, laser scanning microscopy, and 3D shape measurement of manufactured specimens were conducted. As a result, the gained knowledge was applied for the AM-specific redesign of the flexure pivot. Finally, a qualified flexure pivot has been manufactured in a hybrid manner to subsequently ensure its long-term durability in a lifetime test bench.