Process Window And Microstructural Evolution Of Silica-Reinforced Inconel 718 Metal Matrix Composites Fabricated By Laser Powder Bed Fusion

Abstract

In this study, fabrication of Inconel 718 (In718) matrix composites reinforced with 1, 2, and 3 wt.% silica nanoparticles by laser powder bed fusion (LPBF) was investigated. To evaluate the LPBF process window, volumetric energy densities, from -30% to +30% relative to the optimized condition of In718, were applied, and followed by AMS 5663 heat treatment. The relative densities and defects formation were assessed using digital microscopy, while powder morphology, elemental distribution, and in-situ phase formation were examined by SEM|EDS and STEM|EDS. The results showed that silica addition shifts the nearly dense processing condition toward higher energy densities. With higher reinforcement contents, process needs greater energy input to reduce lack-of-fusion defects. STEM|EDS revealed the in-situ formation of Nb-rich silicides and Al|Ti oxides during LPBF. Microhardness increased in the as-built composites compared with monolithic In718, indicating the combined effects of reinforcement addition, in-situ precipitates, and defect-controlled densification.