Effect of pulse frequency on microstructure and properties of laser additive manufactured Inconel 718

Laser additive manufacturing of Inconel 718 nickel-based superalloy (In718) typically results in coarse columnar grains, which adversely affect its mechanical properties. In this study, the microstructure characteristics of In718 were modified by adjusting the pulse frequency to enhance its hardness, tensile properties, and corrosion resistance. The results demonstrate that the appropriate pulse frequency promotes grain refinement, facilitates the transition from columnar to equiaxed grains, and reduces the precipitation of Laves phases. At the pulse frequency of 20 Hz, the partial grain refinement was achieved in In718. Both grain size and aspect ratio were significantly reduced, while Laves phase precipitation was minimized. The sample exhibited the highest hardness, with the tensile strength and elongation reaching 868 MPa and 27.04 %, respectively, along with the optimal corrosion resistance. The approach of the tailoring pulse frequency proves to be an effective method for improving the microstructure and properties of In718. This study provides the theoretical foundation for understanding the influence of grain structure and precipitate distribution on the overall performance of laser additively manufactured In718.