The corrosion behaviors of Inconel 718 fabricated by additive-subtractive hybrid manufacturing in marine environment

Due to the different timing of the intervention in subtractive manufacturing (SM), additive-subtractive hybrid manufacturing (ASHM) primarily includes two subtractive methods: high-temperature milling (HTM) and room-temperature milling (RTM). In the present work, the passive film characteristics and corrosion behavior of Inconel 718 samples prepared by additive manufacturing (AM) and ASHM (including HTM and RTM) were investigated using microstructural, residual-stress, electrochemical, and X-ray photoelectron spectroscopy analyses. Due to the formation of nano-grained microstructure and residual compressive stress introduced by AM, the ASHM-fabricated samples did not undergo obvious stress corrosion cracking after polarization reaction. Furthermore, a significant increase in grain boundary density led to a higher proportion of oxides in the passive film of ASHM-fabricated samples than that of AM-fabricated one, thus improving the film’s compactness and chemical stability. Compared to AM and HTM samples, RTM sample showed the highest grain boundary density, thickest passive film, minimal defects, and superior overall corrosion resistance.