Influence of Crystallographic Texture and Heat Treatment on the Corrosion Performance of Additively Manufactured Inconel 718

Additively manufactured Inconel 718 enables the production of complex components with greater design flexibility than conventional manufacturing methods. The additive manufacturing process produces a microstructure that differs from that of conventionally manufactured Inconel 718, resulting in distinct material properties. One characteristic of the additive process is the development of crystallographic texture, which can vary in intensity from weak to strong. The influence of crystallographic texture on the corrosion behavior of additively manufactured Inconel 718 has received relatively little attention. Likewise, the optimal post-processing heat treatment for additively manufactured Inconel 718 remains under investigation. This thesis therefore aims to investigate the influence of crystallographic texture on corrosion resistance and to evaluate how different heat treatments affect corrosion behavior in combination with texture. Samples were categorized into three texture groups (weak, medium, and strong) and subjected to three different conditions: as-built, direct double aging, and solution annealing followed by double aging. After surface preparation, corrosion behavior was investigated using localized electrochemical techniques, including potentiodynamic polarization, potentiostatic polarization, Mott-Schottky analysis, and electrochemical impedance spectroscopy (EIS). Borate buffer and 3.5 % NaCl solutions were used as electrolytes. Crystallographic texture was characterized using electron backscatter diffraction (EBSD) to correlate the microstructure with the electrochemical results, and scanning electron microscopy (SEM) was used to characterize the microstructure before and after corrosion testing. Among the investigated conditions, samples subjected to direct double aging consistently exhibited the poorest corrosion resistance, whereas the corrosion behavior of the as-built and solution-annealed conditions was broadly comparable, with only minor differences. This suggests that solution annealing followed by double aging may not be necessary in terms of time, costs, and energy if the achieved corrosion resistance is comparable to that of the as-built condition. Although variations in corrosion behavior were observed between the different texture groups, the results suggest that the influence of crystallographic texture is less significant than that of heat treatment. Overall, the results provide a better understanding of how heat treatment and crystallographic texture influence the corrosion behavior of additively manufactured Inconel 718, contributing to the optimization of post-processing routes for corrosion-critical applications.