PBF-LB/M of Inconel X-750: Correlation between crystallographic features, microstructural evolution, and processing parameters

Processing polycrystalline Ni-base superalloys with powder bed fusion using a laser beam (PBF-LB/M) is highly relevant for the transport and energy sectors. Inconel alloys 718, 625, and 939 have been the focus of most research efforts, however, these alloys differ from Inconel X-750. Three aspects were approached in the current work: processability, statistical correlations, and a detailed description of the resulting microstructure. FE-SEM-EBSD, STEM-EDS, and APT were used in addition to the usual methods for additive manufacturing parts. The role of dislocations in the precipitation of primary γ ′ for was found as secondary for this alloy, while the local chemical composition is the likely leading factor. Such is the case that no correlation between the geometrically necessary dislocations (GND) and other quantities. Evidence was found regarding the impact of grain boundary misorientation on the precipitation of η -phase. The effect of the precipitation of the η -phase on primary and secondary γ ′ precipitates is described, as a difference in the chemical composition of both γ ′ precipitates was detected. Lastly, the quantification of the γ , γ ′ and η -phases for AM Inconel X-750, performed through image analysis and H-XRD, is reported here for the first time. • Dislocation density has shown no correlation to microstructure and process parameters. • Evidence on grain boundary misorientation inducing formation of η -phase found. • Precipitation of primary γ ′ -phase strongly influenced by η -phase and dislocations. • Secondary γ ′ -precipitates differs in shape and composition from primary precipitates.