Hot Corrosion Behavior of NiCrAlY Coating in Simulated Flue Gas

NiCrAlY coating was prepared on Super304H steel surface by high velocity oxygen fuel spray. The hot corrosion behavior of the prepared NiCrAlY coatings covered with Na₂SO₄+K₂SO₄+Fe₂O₃ salt film was investigated in simulated flue gas with different content of SO₂ at 650℃. The microstructure and composition of the coating and corrosion products were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results show that the NiCrAlY coating exhibited good corrosion resistance in the simulated flue gas with 0.15% (mass fraction) SO₂. The corrosion rate of the NiCrAlY coating was accelerated with increase of SO₂ content. The corrosion products on the surface of NiCrAlY coating were mainly NiCr₂O₄ and contained a small amount of Fe₂O₃. Due to the corrosive medium diffused inward through coating defects, a sulfur-rich corrosion layer formed at the interface between coating and substrate.