Investigation into the Microstructure and Hardness of Additively Manufactured (3D-Printed) Inconel 718 Alloy

Abstract

Additive manufacturing (AM) of Ni-based super alloys is more challenging, compared to the production other metallic alloys. This is due to their high melting point and excellent high temperature resistance. In the present work, an Inconel 718 alloy was fabricated by a powder laser bed fusion (P-LBF) process and investigated to assess its microstructural evolution, together with mechanical properties. Additionally, the alloy was compared against the cast (and forged) alloy of similar composition. The microstructure of the P-LBF-processed alloy shows hierarchy microstructure that consists of cellular sub-structure (~100–600 nm), together with melt pool and grain boundaries, in contrast of the twin infested larger grain microstructure of the cast alloy. However, the effect of such unique microstructure on mechanical properties of the L-PBF alloy was overwritten, due to the absence of precipitates. The hardness of the L-PBF-processed alloy (330–349 MPa) was lower than that of cast alloy (408 MPa). The similar trend was also observed in other mechanical properties, such as Young’s modulus, resistance to plasticity and shear stress.

Microstructural and Nanoindentation Investigation on the Laser Powder Bed Fusion Stainless Steel 316L

“…As widely reported in literature [19][20][21][22], the microstructure of the additively manufactured metallic materials is exclusive, and completely dissimilar to that of the wrought counterparts of similar compositions. The reason behind that is the high cooling rate during AM, which is a couple of magnitudes higher than that of traditional casting [23,24].…”

“…This is unique to P-LBF alloy as epitaxial grain growth taken place that can be extended among several layers. Hence, grain refinement due to the L-BPF process was not substantial compared to other metallic alloy systems, such as Al [20], Ti [21], and Ni-based super alloys [19]. This may be due to the existence of multiple major alloying elements in the SS316L that influence the melt pool dynamics differently.…”

“…To exploit this research gap, microand nano-indentation techniques were applied in the current study to obtain a similar level of mechanical properties. In spite of the simplicity, micro-and nano-indentations are powerful techniques for finding the micro-and nano-mechanical properties of a given material [19]. This is the novelty of the present work, where a simple yet powerful indentation technique was employed to assess the micro-mechanical properties of L-PBF-fabricated stainless steel 316L.…”

Investigation on Mechanism of Microstructure Evolution during Multi-Process Hot Forming of GH4169 Superalloy Forging

“…GH4169 alloy is a typical Ni-Fe-Cr-based superalloy, which can maintain excellent comprehensive mechanical properties and microstructure stability under high temperatures and high pressure [1][2][3][4]. Hence, GH4169 superalloy is commonly utilized in the production of critical components in the energy and aerospace industries, such as casings and turbine discs [5][6][7][8]. In general, hot deformation, such as die forging and rolling, is the main way to manufacture these components [9][10][11].…”

Crack Inhibition and Performance Modification of NiCoCr-Based Superalloy with Y2O3 Nanoparticles by Laser Metal Deposition

“…As a precipitated strengthening alloy, it can maintain considerable mechanical properties at high temperature. In addition, the high content of Cr also gives the alloy excellent oxidation and corrosion resistance [ 2 ]. Therefore, it is considered a suitable candidate material for ultra-supercritical power generation equipment.…”