Enhancing hot corrosion resistance of NiCrAlYSi coatings by Al-Cr surface modification via chemical vapor deposition (CVD)

A layered coating was fabricated on a nickel-based superalloy via Al-Cr co-deposition using CVD method, following the arc ion plating (AIP) of a NiCrAlYSi layer. Hot corrosion resistance of the Al-Cr modified NiCrAlYSi coatings at 900 °C was investigated in comparison with NiCrAlYSi coatings and Al-Cr coatings. The Al-Cr modified NiCrAlYSi coatings exhibited excellent hot corrosion resistance at 900 °C, little spallation of surface oxides was observed within 200 h. This performance can be attributed to i) the sacrifice-fluxing effect of Al/Cr, ii) the S entrapment mechanism by the addition of Cr, iii) the pinning effect of Y-rich oxides and iv) the suppression of outward diffusion of refractory elements due to the multilayer design.