Independent effects of laser power and scanning speed on IN718's precipitation and mechanical properties produced by LBPF plus heat treatment

Abstract

The laser energy density was believed to control microstructure and mechanical properties of additive-manufactured Inconel 718 (IN718) alloy. However, in this study, remarkable differences were found in the microstructures, tensile mechanical properties, and fracture surfaces of industrial IN718 alloy (with densities higher than 99.75%), which were fabricated by Laser Powder Bed Fusion (LPBF) processes with almost identical laser energy densities and the same standard heat treatment. The results show that these deviations are primarily ascribed to the independent effects of laser power and scanning speed during LPBF-processes on the precipitation of IN718 alloy. The reasons for these variations are discussed based on the thermal history of melt pool and pre-solidified layer during the LPBF-process, which were further analyzed and supported by computational fluid dynamics simulation based on the finite volume method.