Effects of PTA Deposition Parameters on Geometry and Hardness of AISI 316L Single-Tracks

Directed Energy Deposition (DED) is an Additive Manufacturing (AM) technology involving the layer-by-layer building of components close to their final geometry. One of the main applications of DED is the repair of metallic components, however, geometrical control is challenging due to the nature of feedstock, heat source, and the process itself. Within this context, Plasma Transferred Arc (PTA) is a well-known process for applying coating on metallic materials, guaranteeing a good metallurgical bond between the substrate and the deposited material. This study addresses the effects of deposition current and deposition velocity on the geometry of single-track AISI 316L. The relationship between processing parameters, processability, and hardness is identified and discussed as a valuable database to select AM maintenance procedures. A Design of Experiment (DoE) varying two factors was adopted, deposition current (4 levels) and deposition velocity (3 levels), totaling 12 sets of parameters. Statistical analysis reveals that both factors affect substrate dilution, while a higher current increased dilution the velocity had the opposite effect. The results also showed that both deposition parameters greatly affected the wettability, hence the geometry of the single tracks. The DoE allowed for a good predictive estimate of the interaction with a part being repaired and the refurbishing of its geometry by AM. This research points out that the geometry, microstructure, and hardness of the first deposited track play an important role in the quality and properties of subsequent multilayer builds, required to recover the part geometry or even add functionalities.