Impact of laser scanning speed on microstructure and mechanical properties of Inconel 718 alloys by selective laser melting

Inconel 718 alloys were fabricated by selective laser melting under different scanning speeds to investigate the change of the morphology of molten pool, direction of grain growth, and tensile properties. Results show that as the scanning speed increases from 1,000 to 1,450 mm·s⁻¹, the ratio between depth and width of molten pool increases, yet their overlapping regimes decrease. Meanwhile, increasing scanning speed can promote the solidified structure evolve from cell to columnar dendrites, and decrease the dendrite spacing from 0.54 to 0.39 µm; the average columnar grain size also decreases from 84.42 to 73.51 µm. At different scanning speeds, the preferred orientation of grains along the building is mainly <001> direction. In addition, the tensile properties of samples under different scanning speeds present a non-monotonic transition. The maximum ultimate tensile strength and elongation can reach 1,014±19 MPa and 19.04±1.12 (%), respectively, at the scanning speed of 1,300 mm·s⁻¹.