Microstructure Evolution in Direct Energy Deposited Multilayer Inconel 718

The present work is aimed to investigate the microstructure evolution in multilayer Inconel 718 (IN718) superalloy deposited by laser-aided direct energy deposition, which was studied using a scanning electron microscope (SEM). The results show a dendritic morphology with long columnar grains at the bottom and middle regions, while equiaxed structures are observed at the top deposited region. The niobium (Nb)-rich Laves phase formation at the interdendritic area is found in the IN718 superalloy microstructure. Energy-dispersive X-ray spectroscopy (EDS) analysis results confirm severe elemental (Nb, Mo, and Ti) segregation in IN718 deposition. A 17% increase in Nb segregation is observed at the top region, whereas it is only 4% in the bottom region. Additionally, the dendrites' size is increased along with Laves phase quantity as the number of layers is increased. Moreover, the microhardness studies showed a decreasing trend with the increment in layers which could be due to the depletion of strengthening phases in the dendritic nickel (Ni) matrix.

Automated summary

This study investigates the microstructure evolution in multilayer Inconel 718 (IN718) superalloy deposited by laser-aided direct energy deposition using SEM. The results reveal dendritic morphology with long columnar grains at the bottom and middle regions, and equiaxed structures at the top deposited region. Additionally, severe elemental segregation and Nb-rich Laves phase formation were observed in the IN718 microstructure, with an increase in Nb segregation at the top region and a decreasing trend in microhardness with the increment in layers.