Tailoring columnar-to-equiaxed transition in additive manufacturing of Nickel-based superalloys via melt pool control: A theoretical study

Abstract

Tailoring columnar-to-equiaxed transition (CET) in additive manufacturing (AM) or welding of nickel-based superalloys is critical for achieving target mechanical properties. However, maintaining the desired solidification pattern remains challenging due to the highly dynamic nature of the melt pool. This study introduces melt pool features as an intermediate dimension, establishing a “process–melt pool–structure” linkage for real-time monitoring and closed-loop control. Key features such as trailing-point temperature gradient, solidification rate, and width-to-length ratio are defined and correlated with processing parameters using a simple heat-conduction model. The concept of “similar melt pools” is proposed to clarify their effects on solidification conditions. Combined with the classical CET theory, the correlations between melt pool features and final solidification structures are quantified, identifying ranges for stable columnar or equiaxed growth and providing a theoretical basis for solidification control in AM processes.