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.