Hot corrosion behavior of NiCr-Cr3C2-CaF2/BaF2 composite coating with NiAl bond coating in molten NaCl-KCl and NaCl-Na2SO4 at 800 ℃

The NiCr-Cr3C2-CaF2/BaF2 coating with the NiAl bond coating was sprayed on a Ni16Cr13Co4Mo(wt%) alloy by detonation-gun spray, and hot corrosion behaviors were studied by electrochemical measurements. In molten NaCl-KCl, the corrosion products were mainly Cr2O3. Gas phases such as Cl2 led to spallations and cracks on the coating surface. In molten NaCl-Na2SO4, Na2SO4 decomposed and reacted with the coating. Mixed oxides formed a continuous corrosion layer, and Al diffused outward from bond coating to be oxidized. Some liquid phases existed in the corrosion layer and promoted hot corrosion. The detailed hot corrosion mechanisms in two molten salts were discussed.