Effect of Heat Treatment on Microstructure Evolution and Mechanical Properties of Selective Laser Melted Inconel 718 All
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JMEPEG https://doi.org/10.1007/s11665-019-04309-3
Effect of Heat Treatment on Microstructure Evolution and Mechanical Properties of Selective Laser Melted Inconel 718 Alloy Qiang Zhang
, Pan Ren, Xiaohui Tu, Yuhong Dai, Xiaojian Wang, and Wei Li
(Submitted January 10, 2019; in revised form July 13, 2019) The microstructure characteristics of the selective laser melted Inconel 718 alloy under as-deposited, homogenization + solution + aging (HSA) and solution + aging (SA) conditions were studied. The anisotropy and heterogeneity of mechanical properties under different conditions were also investigated. Under the as-deposited condition, the morphology and size of the grains are heterogeneous. The dendrite structures which grow nearly perpendicular to the molten pool traces, accompanying interdendritic Laves phase, can be observed within the grains. The dendrite structure completely disappeared, and the Laves phases embedded in the interdendritic regions also dissolved into the matrix to precipitate c¢ and c¢¢ phases after heat treatments. Fully recrystallized grains were obtained under the HSA condition, while only incomplete recrystallized grains were obtained under the SA condition. However, the characteristics of c¢ and c¢¢ phases are very similar under the HSA and SA conditions. Significant improvement in strength after heat treatments was due to the dissolution of undesirable Laves phase and the precipitation of c¢ and c¢¢ phases. For all the three conditions, different tensile properties were observed depending on the orientation of the specimens. The scatter of mechanical properties is notable, and heat treatments increased the scatter of mechanical properties. Keywords
Inconel 718 alloy, mechanical properties, microstructure, selective laser melting
1. Introduction Nickel-based superalloys have been extensively and successfully used in many industry fields due to their good mechanical properties at room and elevated temperatures. Among the numerous nickel-based superalloys, Inconel 718 alloy is widely used to fabricate the turbine disks, shafts, blades and other high-temperature components (Ref 1, 2). Inconel 718 is a precipitation-strengthened multicomponent, multiphase alloy composed mainly of Ni, Cr, Fe, Nb, Ti, Al and Mo elements, which is mainly strengthened by precipitated c¢¢ (Ni3Nb) and c¢ (Ni3(Al,Ti)) phases (Ref 3–5). However, segregation of high-concentration refractory elements such as Nb and Mo often exists in the Inconel 718 parts produced by traditional techniques (Ref 6), and it is difficult to machine due to the excessive tool wear and low material removal rate (Ref 7). Additive manufacturing (AM) is a type of near-net shaping technique to produce three-dimensional parts (Ref 8). Selective laser melting (SLM) is a powder-bed-based AM process for the manufacturing of complex-shaped metallic parts that are Qiang Zhang, Pan Ren, Xiaohui Tu, Xiaojian Wang, and Wei Li, Institute of Advanced Wear and Corrosion Resistance and Functional Materials, Jinan University, Guangzhou 510632 Guangdong, Peop
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