Numerical Simulations of the Effect of Heat Input on Microstructural Growth for MIG-Based Wire Arc Additive Manufacturing of Inconel 718

The demand for additive manufacturing of large-scale complex parts is challenging to obtain high productivity with excellent properties. Wire arc additive manufacturing is one of the best suitable processes using MIG welding to build large-scale parts efficiently. In this study, Inconel 718 was used for deposits by wire arc additive manufacturing. The objective of the present study is to investigate the effect of heat input on microstructural growth in different regions such as bottom, middle and top of the additively manufactured deposits. The penetration is one of the significant distresses to alter the formation of microstructure and resolution. Penetration is directly proportional to heat input, and shallow and consistent penetrations are recommended for additive manufacturing deposits. The accumulation of heat in the deposited parts leads to heat conduction in the building direction and promotes microstructural growth in that direction. In order to identify the heat conduction in wire arc, additive manufacturing and its effect on grain growth were analyzed by numerical analysis of the weld pool, thermal history, solidification rate (R), and temperature gradient (G). The experiment results revealed the development of equiaxed grains for the low heat input and columnar grains for the high heat input deposits. The microstructural growth is faster with the columnar structure of the anisotropic property, as observed in the high heat input deposits. The simulation results confirmed that a low heat input lead to a higher solidification rate resulting in equiaxed grains than the high heat input deposits.