Development of a stainless steel 3D printing process using PBF

Abstract

This thesis presents numerical and experimental investigations of 3D printing 316L stainless steel structures by Powder Bed Fusion (PBF). First, the process window, i.e., the window of process parameters to fabricate 3D structures without insufficient melting or causing balling, was constructed by varying the laser power and scan speed. Secondly, the relative density depending on process parameters were investigated. Selection of the appropriate process parameters (e.g. laser power, scanning speed, hatching distance, layer thickness) played an important role in determining final properties. Experiments were conducted using an in-house PBF printing system. At the optimal condition, the density of the as-built samples was greater than 98%. Finally, a three- dimensional finite element model (FEM) was performed in this work in order to observe the transient temperature field and melt-pool dynamics. The validity of the model was confirmed by comparing the calculated melt pool dynamics with experimental data. The computation results, together with experimental data, suggest that homogenous melt pool should be formed by laser power 180 W and scanning speed 100 mm/s for effective PBF printing of 316L stainless steel structures.