Additive manufacturing technologies are increasingly gaining traction in the aerospace market due to their ability to produce complex geometries with up to 80% less waste compared to traditional methods like casting and forging. This makes additive manufacturing crucial for sustainable aviation development. The process of interest in this study is the layer-by-layer laser deposition called Directed Energy Deposition (DED) using metal wire or powder. One of the key properties is the microstructure which would preferably have isotropic properties and therefore an equiaxed microstructure to achieve the desired performance. However in additive manufactured components and more precisely with DED components, the predominant grain structure is the dendritic columnar shape, oriented in the scanning direction. To predict the microstructure, a thermal model from an internally developed software that simulates the melt pool geometry is used to extract thermodynamic properties. These properties are then compared to the Columnar-to-Equiaxed Transition (CET) model built by Hunt and adapted by Gaümann. The model requires material properties that are extracted using the CALPHAD-based software Thermo-Calc. This methodology enables the prediction of the grain structure adapted to any type of nickel-based alloys, which becomes a powerful tool for application on newly developed alloys for aerospace. Two methods to trigger an equiaxed microstructure within Ni-based alloys have been identified: process optimization to adjust the thermal gradient and solidification rate, and material optimization to facilitate nucleation of equiaxed grains. The latter can be done through introduction of inoculant particles to create a competition between the growths of columnar and equiaxed grains, following the work of Durga et al. Thermodynamic simulations with Thermo-Calc are used to evaluate the thermal stability of possible inoculants, as well as to evaluate their potential to promote an equiaxed microstructure.