Chemical and mechanical post-processing of Alloy 718 built via electron beam-powder bed fusion: Surface texture and corrosion behavior

Abstract

Alloy 718 specimens manufactured via electron beam-powder bed fusion (EB-PBF) were subjected to post-processing techniques, such as thermal post-treatment and surface finishing. Hot isostatic pressing followed by solution-aging heat treatment (HIP-HT) was used as the thermal post-treatment. Surface finishing techniques, such as turning (TU), shot peening (SP), chemically accelerated vibratory finishing (CAVF), and electro-polishing (EP), were applied on the as-built and HIP-HT specimens. The surface texture of all the specimens was characterized, with the HIP-HT specimen having the highest area arithmetical mean height (Sa) value of 52 ± 1.8 µm and the TU specimen having the lowest at 1.1 ± 0.1 µm. The corrosion performance, typically associated with surface texture, was not always tied to the overused Sa value. CAVF had the highest polarization resistance of 75.8 kΩ.cm2 among the studied methods, followed by TU with polarization resistance of 43.8 kΩ.cm2, showing that the two techniques have a great potential for improving the surface characteristics of the EB-PBF-built Alloy 718 parts.

Keywords

• Electron beam-powder bed fusion
• Ni-based superalloys
• Surface texture
• Surface finishing
• Corrosion performanc