Effect of scanning strategy on grain structure and crystallographic texture of Inconel 718 processed by selective laser melting

doi:10.1016/j.jmst.2018.02.002

Abstract

Abstract:

Two types of scanning strategies were adopted to study the effect of scanning strategy on grain structure and crystallographic texture of selective laser melted (SLM) Inconel 718. The results show that bidirectional scanning without and with a 90°-rotation for every layer produced the bimodal grain structure and the directional columnar grain structure, respectively. Controlling the heat flux direction between the successive layers via scanning strategy enabled the formation of such different grain structures. Furthermore, when the 90°-rotation was applied, the competitive grain growth mechanism became more pronounced and the strong cube texture developed.

Key words: Selective laser melting, Additive manufacturing, Scanning strategy, Texture, Grain structure

H.Y. Wan, Z.J. Zhou, C.P. Li, G.F. Chen, G.P. Zhang. Effect of scanning strategy on grain structure and crystallographic texture of Inconel 718 processed by selective laser melting[J]. J. Mater. Sci. Technol., 2018, 34(10): 1799-1804.

Figures/Tables 9

Fig. 1. Schematic illustration of two types of scanning strategies: (a) scanning strategy X and (b) scanning strategy XY.

Fig. 2. Three-dimensional (3D) optical metallographic (OM) views of the cubic samples fabricated by (a) scanning strategy X and (b) scanning strategy XY.

Fig. 3. EBSD orientation maps taken in the three orthogonal planes of the (a)-(c) scanning strategy X- and (d)-(f) scanning strategy XY- fabricated samples.

Fig. 4. Grain structure observed from the top-view of sample fabricated with scanning strategy XY.

Fig. 5. PF and IPF maps measured from the front-view of samples fabricated with (a), (b)scanning strategy X and (c), (d) scanning strategy XY, respectively.

Fig. 6. High-magnification SEM back scatter electron (BSE) image of the cellular structure of the scanning strategy XY-fabricated sample.

Fig. 7. Microstructure characterization: (a) BSE image, (b) IPF map and (c) BC map taken in the same region of scanning strategy X-fabricated sample.

Fig. 8. Microstructure characterization: (a) BSE image, (b) IPF map and (c) BC map taken in the same region of scanning strategy XY-fabricated sample.

Fig. 9. Schematic illustration of the effect of scanning strategy on grain structure and crystallographic texture: (a) the maximum temperature gradient directing toward the normal of the fusion line in a single track, (b) the angle between the maximum temperature gradient with the three <001> preferred growth directions, (c) and (d) schematic illustration of grain structure in scanning strategies X- and XY-fabricated samples, respectively.

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