Microstructure and mechanical properties of the Inconel 718 superalloy manufactured by selective laser melting

Abstract

The work is devoted to the study of the microstructure and mechanical properties of the nickel base superalloy Inconel 718 manufactured by selective laser melting (SLM). Multiple cycles of heating and cooling during SLM led to the formation of a complex microheterogeneous microstructure. The microstructure of the superalloy manufactured by SLM consisted of elongated γ grains with a transversal size of 10 -100 μm and a longitudinal size of 50 -300 μm, which in its turn consisted of columnar and equiaxed subgrains. Stable and metastable precipitates of the δ-Ni 3 Nb and γ''-Ni 3 Nb phases, carbides and probably oxides, were detected along the subboundaries. The standard heat treatment of the superalloy manufactured by SLM resulted in a partial dissolution of the δ phase and the metastable γ'' phase during solid solution treatment and precipitation of the dispersed metastable γ'' phase during ageing. The microstructure characterization performed by electron backscatter diffraction technique (EBSD analysis) revealed that the size and elongated form of the γ grains was not changed after the heat treatment, the size of the subgrains slightly increased, the fraction of low-angle boundaries (subboundaries) decreased, and the fraction of high-angle grain boundaries increased. Tensile tests were carried out at T = 20 -700°C for the superalloy samples subjected to standard heat treatment. The tensile direction was parallel to the building direction. The tensile tests showed that the superalloy manufactured by SLM exceeded the requirements of the AMS 5662 certificate for the superalloy Inconel 718 in a hot forged condition subjected to standard heat treatment.

Modification of Mechanical Properties in Directed Energy Deposition by a Static Magnetic Field: Experimental and Theoretical Analysis

“…Gamma phase is observed as the main phase in Figure 9 , which is also mentioned in [ 4 , 22 , 42 , 43 ]. The XRD analysis revealed no presence of Ni 3 (Al, Ti), Ni 3 Nb, and intermetallic Laves ((Ni, Cr, Fe) 2 (Nb, Mo, Ti)) phases [ 4 , 44 , 45 ].…”

Conductivity Modulation of 3D‐Printed Shellular Electrodes through Embedding Nanocrystalline Intermetallics into Amorphous Matrix for Ultrahigh‐Current Oxygen Evolution

“…The obvious diffraction rings in the SAED pattern (Figure 3f inset) can be indexed to the contribution of polycrystalline nanocrystals (Ni 3 Nb), and two distinct diffraction rings can be identified as the (204) and (034) planes of the body‐centered tetragonal (BCT) Ni 3 Nb structure. [ 15,23 ] The regularity of the lattice plane in the HRTEM image (Figure 3g) clearly indicates that the nanocrystalline Ni 3 Nb are single crystals. The space between adjacent planes, 0.258 nm, is consistent with the (102) plane of BCT Ni 3 Nb.…”

“…The nanocrystallites are well dispersed in the amorphous matrix, which is in good agreement with the bottom region of the activated layer (Figure3e). The obvious diffraction rings in the SAED pattern (Figure3finset) can be indexed to the contribution of polycrystalline nanocrystals (Ni 3 Nb), and two distinct diffraction rings can be identified as the (204) and (034) planes of the body-centered tetragonal (BCT) Ni 3 Nb structure [15,23]. The regularity of the lattice plane in the HRTEM image (Figure3g) clearly indicates that the nanocrystalline Ni 3 Nb are single crystals.…”