Melt pool geometry dependent microstructural evolution induced by inoculants in IN718 processed by selective laser melting

This preliminary study aims to clarify how Co, TaCr2 and TiB2 grain refinement inducing inoculants influ-ence the melt pool physics and resulting grain structure in superalloy IN718 processed by laser powder bed fusion (L-PBF). It was demonstrated that the presence of solid inoculant particles could affect the melt pool convection leading to a noticeable reduction in the melt pool width and penetration depth as well as the balling phenomenon. Interestingly, it was found that the penetration depth of the melt pool in samples containing TiB2 appeared to be unchanged due to the presence of nano-particles. Characterization of the resulting grain structures of the various samples revealed that the difference in melt pool geometries contributed to a predominant columnar-grained structure with < 101 > texture in samples containing Co or TaCr2 inoculants while an equiaxed-grained structure with < 001 > texture in samples containing TiB2 inoculants. The effectiveness of inoculants was found to be closely related to their impact on the melt pool physics, in addition to the degree of lattice disregistry with the IN718 matrix.(c) 2022 Elsevier B.V. All rights reserved.