Edge effects in radial porosity profiles from CT measurements and melt pool signal intensities for laser powder bed fusion

Limited process control can cause metallurgical defect formation and inhomogeneous relative density in laser powder bed fusion manufactured parts. In this study, cylindrical 15-5 PH stainless steel specimens are investigated by computer tomography; it shows an edge enhanced relative density profile. Additionally, the on axis monitoring signal, obtained from recording the thermal radiation of the melt pool, is considered. Analyzing data for the full duration of the building process results in a statistically increased melt pool signature close to the edge corresponding to the density profile. Edge specific patterns in the on axis signal are found by unsupervised times series clustering. The observations are interpreted using finite element method modeling: For exemplary points at the center and edge it shows different local thermal histories attributed to the chosen laser scan pattern. The results motivate a route towards future design of components with locally dependent material parameters.