Single-crystalline Ni-based superalloy builds using laser-directed energy deposition (L-DED): A multi-scale modeling and experimental approach

Additive manufacturing is rapidly becoming a viable alternative for producing complex geometries, making it a potential choice for manufacturing aerospace components. The high-pressure turbine blades in a jet engine not only have complex geometry but also require stringent microstructural specifications such as single-crystallinity. The combination of complexities in the topology and microstructure makes it challenging to identify the right process parameters for the additive manufacturing of these blades. In this paper, we describe an innovative workflow for identifying these parameters, involving physics-based modeling at the melt pool length scale and microstructure modeling at the grain and dendritic length scales. We introduce a novel diffuse-interface-inspired model to simulate the melt pool shape during multi-layer additive manufacturing. The thermal histories obtained from this model are used in a Potts-based microstructure model to determine the approximate texture during solidification. By combining the process and grain-scale model, we determine the parameter space for single-crystalline builds. Experimental analysis confirms that the identified parameters yield single-crystalline microstructures. Furthermore, the thermal histories are utilized in phase-field simulations that consider all the components of the CMSX-4 alloy to determine the primary dendrite arm spacing (PDAS), which, upon comparison with experimental measurements, serves as validation of the solidification conditions derived from the process model. Thus, the complementary use of modeling and experiments provides insights that allow the identification of appropriate additive parameters for epitaxial growth and aid in designing strategies for building complex shapes.