Insight into the passivation and corrosion behavior of additive manufacturing repaired single crystal superalloy

The passivation and corrosion behaviors of additive manufacturing repaired Ni-based single crystal superalloy were analyzed by comparison with the substrate. We found that the cladding layer is comprised of fine cellular dendrites (FDs) and fine cellular interdendritic zones (FIDZs) with abundant nano particles of γ′(Ni3Al) phase. The cladding layer possesses thicker passive film which gives better protection to the cladded component. The FIDZs are more sensitive to corrosion because of the dissolution of Nb-rich and Cr-Mo depleted zones in FIDZs. The γ/γ′ couples in the substrate tend to form mesh-like corrosion morphologies due to the selective dissolution of γ′ phases. [Display omitted] •The repaired layer has thicker passive film and better corrosion resistance than the substrate.•The repaired layer has fine cellular dendrites and interdendritic zones with abundant γ′ nanoparticles.•The fine cellular interdendritic zones are subjected to higher degree of corrosion.•The γ/γ′ couples in the substrate are apt to form mesh-like corrosion morphology.