Surface Feature Characteristics of Laser Powder Bed Fusion of Nickel Super Alloy 625 Bulk Regions

Coherence scanning interferometry (CSI) and scanning electron microscopy (SEM) surface inspection of additively manufactured nickel super alloy 625 reveal features over a broad range of length scales beyond those typically reported. High resolution measurements show micrometer-scale dendritic periodicity over 10’s-of-micrometers length scales, often with a circular geometry. Larger-than-anticipated solidified melt tracks are observed near laser path turnarounds, presumably resulting from fusion of adjacent melt pools and cooling rate differences. The dendritic texture variability directly indicates microstructure variation, and further microstructure variation is likely correlated with the melt pool variation, as well. This raises concerns about final material properties and homogeneity.