By employing additive manufacturing (AM) in general and selective laser melting (SLM) in particular, it is possible to produce metallic parts and components of high complexity. In order to reach the efficiency of conventionally manufactured parts, additively produced parts must fulfil at least the same requirements. Therefore, basic investigations for coating and composite systems are essential to obtain a comprehensive understanding of the process-microstructure-mechanical properties of IN 718 and 316L alloys processed by SLM.
Surface quality after SLM
Surface quality of SLM process is still a key issue during the fabrication of the metallic parts. The surface roughness depends not on the process parameter itself, but also on the orientation of the parts in the building chamber. The surface roughness of AM parts has been in the focus of several studies. However, only little research has been performed to characterize the impact of the surface roughness on the coatability of AM parts as well as on the fatigue strength of the overall composite system. Therefore, a deep understanding of the surface properties after SLM is required in determining their effects on the mechanical properties and in designing components with improved performance.
In order to apply AM components under conditions comparable with conventionally produced components in the future, equivalent prerequisites must be created with regard to the post-treatment and the further manufacturing process steps. Most of the metallic components used in high performance conditions, under heat, wear, or corrosive load, are enhanced by adapted heat treatments (e.g. hardening) or (protective) coatings. Through targeted surface functionalization by means of coatings and the adaptation of the layers to the substrate material, the performance characteristics of the entire component are decisively influenced. Most of the components produced by SLM are intended for applications with high mechanical, thermal or corrosive loads. Residual stress can be found in components manufactured by SLM. Therefore, in this project the reason for the evolving of residual stresses and their influence on the coatability of AM parts are explored. Different SLM specimens will be coated by means of High Velocity Oxy-Fuel (HVOF) spraying, Physical Vapour Deposition (PVD) as well as Atmospheric Plasma Spraying (APS). Afterwards, experimental methods are used to measure the residual stress profiles in a set of test specimens with different conditions.