Preparation and microstructural examination of additively manufactured alloys 316L and 17-4PH

Several samples made of the stainless steels AISI 316L and 17-4PH (equivalent to AISI 630) in different compositions were investigated as part of the Collaborative Research Center/Transregio (TRR) 375 on Multifunctional High-Performance Components made of hybrid porous materials (HyPo). The samples were manufactured under the subproject B01 at the Institute for Manufacturing Technology and Production Systems (Fertigungstechnik und Betriebsorganisation, FBK) by laser metal deposition. Individual blocks consisting of four welding layers which are, in turn, composed of eight printed tracks, respectively, were built using different powder compositions. The powder mixture was gradually varied from 100 % 316L to 100 % 17-4PH. This contribution addresses the specifics of visualizing the microstructure of samples with different material compositions. One challenge lies in selecting the appropriate etchants for the samples made of mixed powders. For the investigations, the samples were embedded as longitudinal and transverse sections. Various etching solutions were then tested to visualize the microstructure. The results of the etching experiments and the light micrographs are presented and interpreted based on the findings of energy-dispersive X-ray spectroscopy (EDS) analyses in the scanning electron microscope. They can be used to derive strategies for adjusting the microstructure of graded samples which may serve in the future to obtain specific properties.