The possible role of nano sized precipitates on the mechanical properties of additively manufactured IN 718 superalloy

Abstract

In the present study, three dimensional parts of Inconel 718® (IN 718) superalloy were fabricated using laser powder bed fusion (L-PBF) additive manufacturing (AM). The soundness of the as-built parts was checked by measuring the relative density using Archimedes method. Tensile tests were carried out at the strain rate of 4.6 × 10-3 s-1 at ambient temperature on cylindrical samples extracted from the large size 3D blocks of AM IN 718. Tensile tests were also carried out employing the same test parameters on the wrought counterpart of IN 718 (W IN 718) so as to compare their mechanical properties. The AM IN 718 exhibited about 15% increase in 0.2% yield strength (0.2%YS) as compared to W IN 718. Microstructures of AM IN 718 and W IN 718 were characterized using electron back scattered diffraction. The dislocation substructure of pre-deformed samples was examined using transmission electron microscope (TEM). Bright field TEM images revealed nano-sized precipitates in AM IN 718 and carbides in W IN 718. The marginal increase in 0.2%YS in AM IN 718 is attributed to the impediment to dislocation movements by nano-sized precipitates and high initial dislocation density.