Dimensionless Parameters to Define Process Windows of Selective Laser Melting Process to Fabricate Three-Dimensional Metal Structures

Despite the intense research attention on the three-dimensional printing of metal structures via selective laser melting, a unified understanding of thermal conditions, and more specifically the input energy levels, necessary for minimizing macroscopic-defect generation is still lacking. Although simple and widely used parameters, such as linear or volumetric energy density, can be utilized to represent the characteristic energy level of the process, notable differences in printed morphologies and microstructures are observed in structures fabricated at the same energy density. Consequently, designing a process in terms of laser power and scan speed is largely based on trial-and-error approaches. In this work, based on the dimensional analysis of reported experimental data and nu-merical computation, the process windows suitable for the fabrication of single tracks were examined for various metals. In addition to the normalized enthalpy that quantifies the input energy level, another dimensionless parameter which measures the thermal penetration depth relative to the thickness of powder layer was found to be critical in defining the process window that resulted in acceptable single-track structure formation. To confirm the validity of the analysis, via the elimination of uncertainties and ambiguities inherent to the empirical data, numerical computations were conducted for single-track fabrications using Ti-6Al-4 V and 316L stainless steel alloys. The results of the numerical simulations showed good agreement with the findings obtained from the empirical data.