A Study on Microstructure and Mechanical Properties of Inconel 718 Superalloy Fabricated by Novel CMT-WAAM Process

The integration of Inconel 718 (IN718) and Cold Metal Transfer (CMT) based wire + arc additive manufacturing (WAAM) for wall fabrication with a near-net shape and low buy-to-fly ratio presents a novel and promising approach with potential applications in various industrial sectors, including aerospace and automotive industries. This research aims to investigate the microstructure and mechanical anisotropy of thin-walled IN718 components that were produced using CMT based WAAM, and to compare the properties of as-deposited and heat-treated samples that underwent aerospace (AMS5663) procedures. To characterize the microstructure of the specimens, we employed optical microscopy and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and an element probe microanalyzer (EPMA). Tensile and hardness tests were conducted to evaluate the mechanical properties of the specimens. Our results revealed that the as-deposited samples exhibited a dendritic microstructure with a high degree of segregation, leading to lower mechanical strength than that of the heat-treated specimens. Precipitated heat treatment promoted the precipitation of strengthening phases, such as gamma prime and carbides, improving the mechanical properties. In contrast, the precipitated heat-treated specimens exhibited a more refined microstructure with equiaxed grains and a significantly enhanced mechanical strength. This study provides critical insights into optimizing the material for different applications, leading to the development of more efficient and effective parts.

Keywords:
CMT WAAM; Inconel 718; heat treatment; microstructure; mechanical properties