Microstructure control of Additively manufactured IN718 By L-PBF process

ABSTRACT

Additively manufactured (AM) parts generally exhibit large columnar grains and a preferential crystallographic texture. While this microstructure may have beneficial effects, for instance on creep properties, the resulting mechanical anisotropy remains a key issue for most critical in-service applications. The relationship between the solidification conditions and the melt pool morphology of the Inconel 718 fabricated by laser powder bed fusion (L-PBF) was investigated to adapt the microstructural characteristics of the parts to their intended applications. By optimising the length of the scanned vectors, it is possible to reduce both the texture index and the grain size by a factor 2 based on EBSD analyses. In addition, the aspect ratio and the grain density can be increased by a factor 1.1 and 2.2, respectively, compared to a conventional L-PBF scanning strategy. These achievements pave the way for the production of fully isotropic parts and/or anisotropic parts controlled by the L-PBF process.

KEYWORDS:

• Additive manufacturing
• nickel based superalloy
• microstructure control
• texture control
• solidification
• electron backscattered diffraction

Acknowledgements

This study was proposed by the Centre des Matériaux of Mines ParisTech – PSL University to Additive Factory Hub, a French industrial additive manufacturing consortium. It was funded by AddUp under a CIFRE Ph.D. The authors would like to thank M. Simoes and F. Gaslain for the assistance with the EBSD analysis.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

L. Lacoste

L. Lacoste, a PhD fellow at Mines ParisTech and a research engineer at AddUp Solutions, works on the solidfication of the Inconel 718.

A. Sakly

A. Sakly, a research engineer at AddUp Solutions.

S. Dépinoy

S. Dépinoy, a tenure track of Mines ParisTech, works on metallurgy and L-PBF process.

S. Lebel

S. Lebel, the head of material at AddUp Solutions.

B. Vayre

B. Vayre, the head of Research & Development at Addup Solutions.

C. Colin

C. Colin, a research teacher at Mines ParisTech, works on the L-PBF process.