Effect of laser power and scanning speed on the microstructure and mechanical properties of SLM fabricated Inconel 718 specimens

Abstract

Selective laser melting (SLM), one of the main additive manufacturing techniques for metal materials, owns a series advantages in the fabrication of complex components with high precision and short procedure.1–4 It is being widely used in aero plane, aerospace, medical equipments and automotive industries. Fabrication of nickel based super alloy Inconel 718 by SLM is one of the most active research areas in additive manufacturing. The researches focus on the investigation of effect of fabrication parameters on the pore defect, microstructure and mechanical properties. The scanning speed and input power of laser beam are two key factors for the quality of parts. Qiu et al.,5 found that the laser power was in a positive relationship with the fabrication capability of strut diameter while the laser scanning speed had the nonlinearly inverse effect. Wu et al.,6 concluded that reducing the scanning speed and increasing the laser power could effectively increase the amount of remelting and make dense parts. Deng et al.,7 found that the SL Med Inconel 718 specimen had fine cellular-dendrites and relatively weak texture. Vertically built samples showed lower tensile strength but higher ductility than horizontally built samples, which may be caused by their different levels of residual stress and numbers of dislocations. Mclouth et al.,8 found that the laser focal shift used in SLM can change the microstructural morphology by altering the laser’s interaction with the material. Strossner et al.,9 observed niobium micro segregation in the dendritic microstructure. Chlebus et al.,10 found the as-built specimens was characterized by columnar grains of supersaturated solid solution with internal micro segregation of Nb and Mo. In this paper, the effect of laser power and scanning speed on the pore defection, microstructure and mechanical properties of Inconel 718 samples were investigated.