Investigation on the Precipitates of IN718 Alloy Fabricated by Selective Laser Melting

Abstract

The microstructure and precipitates of INCONEL 718 alloy (IN718) fabricated by selective laser melting (SLM) are investigated. The matrix is comprised of the elongated γ grains along Z direction, tilting a few degrees. The microstructure mainly consists of a cellular–columnar structure with fine first dendrite arm space of 1–1.5 µm originated from the rapid solidification rate locally. The precipitates of the SLMed IN718 are confirmed to be a significant amount of Laves in the form of irregular bulk distribution, small amount of carbonitride and spherical Al2O3 particles in nanoscale. Some of the carbonitrides grow separately and some of the carbonitrides enwrap the Al2O3 fully or partly, forming the shell structure of the Al2O3–carbonitride. The reheating effect from the following layers to the previous layers have not reached the solid-state transformation temperature of the γ′ and γ″.