Impact of Laser Power and Scanning Velocity on Microstructure and Mechanical Properties of Inconel 738LC Alloys Fabricated by Laser Powder Bed Fusion

The microstructure and mechanical properties of Inconel 738LC fabricated by laser powder bed fusion (LPBF) were investigated in this work. Three processing parameters were chosen with a specific volumetric energy density of 55.56 J/mm³ input but varying scanning velocity and laser power. The electron backscatter diffraction (EBSD) results revealed that the fraction of the recrystallized grains increased by 15% and the average grain size became smaller with the increased scanning velocity and laser power. Moreover, it was found that the first dendrite arm spacing also showed a slight difference caused by cooling rate variation. Vickers hardness of three sets of parameters varied from 367.6  ± 8.0HV to 396.5  ± 10.9HV. The tensile test results also indicated that better mechanical properties were achieved by choosing a high-speed scanning speed strategy. In addition, computational fluid dynamics (CFD) was performed to verify the melt pool morphology and cooling rate distribution. The CFD results revealed that the more uniform cooling rate distribution caused by low-speed scanning velocity in the melt pool resulted in smaller surface tension of the liquid phase.