Additive manufacturing of nickel-based superalloy Inconel 718 by selective electron beam melting: Processing window and
- PDF / 713,570 Bytes
- 10 Pages / 584.957 x 782.986 pts Page_size
- 51 Downloads / 268 Views
Carolin Körner and Robert Friedrich Singer Department of Materials Science, Chair of Metals Science and Technology, University of Erlangen-Nuernberg, Erlangen 91058, Germany (Received 27 March 2014; accepted 17 July 2014)
Cube-shaped IN718 samples were produced by selective electron beam melting (SEBM) with varying beam power, deflection speed, and beam spot size. Process parameter windows were identified where fully dense samples are obtained with no surface unevenness. High deflection speeds were demonstrated to result in smaller demand of area energy. This result is explained by the reduced time for heat dissipation into the substrate during hatching. The grain structure was strongly affected by SEBM process parameters. Under certain conditions, epitaxial growth over many layers and well-developed columnar grain structures were obtained with a polycrystalline substrate plate. A more defocused beam led to a lower melt pool temperature and shallower melt pool geometry where maximum temperature gradients and solidification rates were more or less in parallel with the building direction and primary dendrite arm orientation. These conditions help to suppress grain nucleation ahead of the nucleation front as vigorous melt movement, fragmentation of dendrites, and tertiary arm growth are suppressed.
I. INTRODUCTION
Additive manufacturing (AM) has attracted considerable interest in the public and industrial sector over the past decades.1 AM allows to produce complex geometries that cannot be accomplished with standard manufacturing techniques like casting or forming. In contrast to established processes, in AM, no expensive molds or dies are necessary for fabrication, opening a potential for cost reduction in small runs. Since AM is a layer-by-layer technique, it can fulfill society’s wish for customization of components and products. Among AM techniques, selective laser melting (SLM) is the one researched most extensively. The present paper will investigate an alternative heat source, namely selective electron beam melting (SEBM). SEBM possesses a number of potential advantages over SLM. First, heat input is more effective as the electron beam is able to penetrate more deeply into the material and the evaporation limitation is averted. Second, the beam deflection speed in SEBM is much higher, as the beam is deflected by electromagnetic lenses rather than by mechanical mirrors and lenses in SLM. In the present study, SEBM was used to process the nickel-based superalloy Inconel 718. With the aim to a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2014.192 J. Mater. Res., Vol. 29, No. 17, Sep 14, 2014
http://journals.cambridge.org
Downloaded: 05 Mar 2015
increase the build-up rate, beam deflection speeds up to 2200 mm s1 are investigated. By the fabrication of simple cube-shaped test specimens, suitable processing parameters are identified. In the literature, several authors reported processing of IN718 with AM techniques. The focus was laid on the relation between microstructure
Data Loading...
