Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Mechanical Performance of Inconel 625 Alloy Processed by L-DED Additive Manufacturing
Submission Author:
Juliane Ribeiro da Cruz Alves , SP
Co-Authors:
Juliane Ribeiro da Cruz Alves, Henrique Santos Ferreira, Anselmo Thiesen Junior, Jurandir Sousa
Presenter: Juliane Ribeiro da Cruz Alves
doi://10.26678/ABCM.COBEM2023.COB2023-1350
Abstract
Inconel 625 is a nickel-based superalloy whose strengthening originates from solid solution hardening promoted by the additions of Cr, Mo, Nb and C, and by the precipitation hardening induced by the formation of intermetallic phases and carbides. Due to its high mechanical strength, oxidation resistance and outstanding corrosion performance, this alloy finds widespread applications in nuclear reactors components and in marine, aeronautic, aerospace, chemical and petrochemical industries. Nevertheless, the high ductility, toughness, hardness and intrinsic abrasiveness of this alloy reduces its machinability, making its processing by conventional techniques challenging. This work investigates the microstructure and mechanical properties of an Inconel 625 multilayer material processed by additive manufacturing (AM) using the laser direct energy deposition (L-DED) process, in the as-built and heat-treated conditions (900°C for 2 h followed by furnace cooling). Microstructure was characterized by optical and scanning electron microscopy and chemical composition by energy dispersive x-ray spectroscopy (EDS). Mechanical properties were assessed by Vickers hardness measurements, tensile tests and Charpy impact tests. The effects of build orientation (vertical or horizontal) and heat treatment are discussed, and AM L-DED results are benchmarked to those of wrought Inconel 625 reported in literature. In the as-built condition, samples developed a dendritic structure with Mo and Nb-rich interdendritic constituents, where Laves phase precipitates were preferentially formed. This microstructure resulted in a similar Charpy energy absorption as the wrought Inconel 625 alloy, used as a reference. Tensile results showed that the specimens built in the horizontal orientation developed a more refined structure associated to higher cooling rates, and exhibited a higher hardness and superior yield strength, ultimate tensile strength, and elongation in comparison to the vertical orientation specimens, whose microstructure was coarser. After heat treatment, partial recrystallization of the dendritic microstructure occurred, leading to segregation of intermetallic precipitates to grain boundaries. This caused a 38% reduction in Charpy energy absorption (from about 72 J to 45 J). Although the heat treatment slightly decreased the hardness and, consequently, the yield strength of the specimens, their ultimate tensile strength was not significantly affected, with all AM L-DED samples showing superior yield strength and ultimate tensile strength than the reference material. This work shows that samples processed by AM L-DED have a competitive performance in terms of mechanical properties in comparison with the commercial Inconel 625, and contributes towards a better understanding regarding the microstructure and properties of the parts manufactured under this complex thermo-mechanical dynamics.
Keywords
Ni-based superalloy, Laser processing, grain boundary embrittlement, Microstructure refinement, build orientation, Mechanical Performance
