The corrosion behaviours of plasma-sprayed Fe-based amorphous coatings

Fe-based amorphous coatings are increasingly recognised as promising candidates for the protection of coal-fired boilers against corrosion. The present study prepared Fe-based amorphous coatings on a T91 substrate by plasma spraying technology. The corrosion behaviour of the coating in hot Na 2 SO 4 + K 2 SO 4 salts at 700°C was investigated, and measurements of the mean mass gain were performed after each cycle to establish the hot corrosion kinetics of the coatings using the thermogravimetric technique. The coated specimens, especially specimens with 380-μm-thick coatings, exhibited lower mean gain rates at all operating cycles as compared to the uncoated T91 samples. The highest hot corrosion resistance was a result of the amorphous composite microstructure and high Cr and Ni elemental contents, which contributed to the formation of the protective oxides of chromium and nickel such as Cr 2 O 3 , NiO and NiCr 2 O 4 .