Investigations of γ′, γ″ and δ precipitates in heat-treated Inconel 718 alloy fabricated by selective laser melting

Abstract

Inconel 718 alloy samples were fabricated by selective laser melting (SLM). Microstructure and precipitation in solution-heat-treated-and double-aging-SLM-made Inconel 718 were studied by scanning and transmission electron microscopy. Electron microscope observations showed that disc-shaped and cuboidal γ″, and circular γ′ precipitates with an average size of 10-50 nm developed within cellular γ austenite matrix. The simulated, experimentally observed electron diffraction patterns, and dark-field imaging further revealed that the precipitation of three variants of γ″ in the γ matrix occurred. The coarser acicular γ″, and globular as well as plate-like δ phases precipitated at grain boundaries and also within the interior of austenite matrix. The morphology, distribution and crystallography of these precipitates and their formation mechanisms were analyzed and discussed. Investigations of γ′, γ ″and δ precipitates in heat-treated Inconel 718 alloy fabricated by selective laser melting." Materials Characterization 136 (2018): 398-406. AbstractInconel 718 alloy samples were fabricated by selective laser melting (SLM).Microstructure and precipitation in solution-heat-treated-and double-aging-SLM-made Inconel 718 were studied by scanning and transmission electron microscopy. Electron microscope observations showed that disc-shaped and cuboidal γ″, and circular γ′ precipitates with an average size of 10 -30 nm developed within cellular γ austenite matrix. The simulated, experimentally observed electron diffraction patterns, and dark-field imaging further revealed that the precipitation of three variants of γ″ in the γ matrix occurred. The coarser needle-like γ″, and globular as well as plate-like δ phases precipitated at grain boundaries and also within the

Laser Powder Bed Fusion of Inconel 718: Residual Stress Analysis Before and After Heat Treatment

“…δ has the same chemical formula of the ɣ'' phase, er, it is incoherent with the ɣ matrix [12]. Large amounts of δ phase are detrimental to al properties, while moderate amounts can be beneficial to the notch sensitivity of the Large carbides and Laves phases negatively affect the mechanical performance of the hases can also exist in the as-built state and therefore to dissolve them a further heat equired [18,20,21]. lve the undesired phases, precipitate the strengthening phases, and consequently echanical properties of the material, a solid solution annealing (SA) plus double ageing atment is required [22].…”

“…In l plane, the scanning tracks are usually observed as continuous lines [18,19,[22][23][24][25]. The e in the as-built condition usually exhibits epitaxial growth of columnar grains columnar or cellular dendrites along the built direction, owing to the high cooling rates process (10 6 K/s [19,26]) and the heat dissipation direction, i.e., vertically through the 21,27]. et al [25,28] studied the microstructure of IN718 parts fabricated by PBF-LB in as-built treated conditions, revealing carbides, Laves phases, and segregations; therefore, heat e crucial to homogenize the microstructure.…”

“…Large carbides and Laves phases negatively affect the mechanical performance of the part. These phases can also exist in the as-built state and therefore to dissolve them a further heat treatment is required [18,20,21].…”

“…Melt pool characteristics of parts fabricated by PBF-LB ar magnification. They are characterized by an arc-shaped or "fish-scale corresponding to the melt pool profile influenced by the Gaussian di the horizontal plane, the scanning tracks are usually observed as con microstructure in the as-built condition usually exhibits epitaxia including fine columnar or cellular dendrites along the built direction of the PBF-LB process (10 6 K/s [19,26]) and the heat dissipation direc substrate [13,21,27].…”

Influence of Heat Treatment on Microstructures and Mechanical Properties of NiCuCrMoTiAlNb Nickel-Based Alloy

“…It can be generally accepted that the ability of appropriate heat treatment to enhance the mechanical properties of Ni-based alloys results from precipitation of intermetallic phases. As for most of the heat-resistant nickel-based superalloys, appropriate heat treatment is able to result in the precipitation of intermetallic phases, including gamma prime (γ ), gamma double prime (γ ), or delta (δ) [20,22]. In general, γ phase, whose chemical composition is based on Ni 3 (Al,Ti), possesses a face-centered cubic (FCC) structure, and the chemical composition of both γ and δ phases is based on Ni 3 Nb, where γ phase belongs to the body-centered tetragonal (BCT) structure, but δ phase possesses an orthorhombic structure [23,24].…”