Effect of scanning strategy and speed on the microstructure and mechanical properties of selective laser melted IN718 nickel-based superalloy

Abstract

In the present study, the properties of selective laser melted IN718 superalloy specimens, prepared by using different processing parameters, were investigated. The scanning strategy (island strategy with and without 30° interlayer rotation and continuous bi-directional scanning with and without 90° interlayer rotation) and scanning speeds of 500, 700, and 1000 mm/s were selected as variables to prepare the superalloy samples. Then, the microstructure and mechanical properties (hardness and compressive strength) were characterized. The results showed, in a given scanning strategy, the density decreases as the scanning speed increases. Also, the island strategy with interlayer rotation during fabrication process leads to a higher level of density (near full density, about 8.20 g/cm3). Interlayer rotation resulted in a more uniform structure by re-melting of deposit layers in different directions during deposition of next layers in both scanning strategies. The higher values of hardness and compressive yield strength were obtained from the samples produced using continuous scanning strategy. Among the investigated samples, the sample produced with continuous scanning strategy with 90° interlayer rotation, 500 mm/s scanning speed has the highest value of hardness, 330 Vickers, and compressive yield strength, 686 MPa.