Influence of specimen position on the build platform on the mechanical properties of as-built direct aged electron beam melted Inconel 718 alloy

Electron powder bed fusion (E-PBF) allows for manufacturing of near-net-shape components of unprecedented complexity. In order to transfer specific benefits into industrial environments, equal properties of any volume built are mandatory. The main objective of this work is to investigate the process-induced material properties in arbitrary build envelope positions. Microstructure, hardness, relative density and fatigue behavior are in focus and thoroughly studied for E-PBF manufactured Inconel 718 alloy. In particular, it can be stated that all specimens have an effective diameter below dimensions set in the initial CAD data. Furthermore, it could be demonstrated that the relative density varies at different positions of the building platform, even for specimens built in direct vicinity. In terms of hardness, specimens at the outer perimeter of the building platform show increased values indicating a higher fraction of strengthening phases. Based on the cyclic tests, a relationship between building platform position and fatigue behavior can be derived. Specimens located in the front of the building platform show superior cyclic properties as compared to specimens in the back of building platform. Notch effects, i.e. process induced topography, are revealed to be the most detrimental influencing factor in the condition tested.