Ceria-Doped Cr3C2–NiCr Coatings on Austenite Steel for Investigation in Actual Boiler Environment.

To obtain better hot corrosion resistance for superheater tube material (TP347H), different wt% of cerium oxide (CeO₂) powder (0.4 wt%, 0.8 wt%, and 1.2 wt%) was blended with Cr₃C₂–NiCr and formulated on TP347H substrate with HIPOJET-2700 thermal spray gun. The comparative effect of different contents of Ce on corrosion and erosion behaviour was studied by weight change measurements, and X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and X-ray mapping tools were used to examine corrosion products. The results show that the appropriate addition of cerium oxide can reduce scale spallation and microporosity and enhance the microhardness and surface roughness of the composite coating. Cr₃C₂–NiCr coatings with and without the addition of CeO₂ successfully protected the substrate steel, which might be due to the development of a dense and continued oxide scale composed of Cr₂O₃ and NiCr₂O₄. Moreover, it is observed that the addition of CeO₂ with 0.4 wt% concentration enhanced the degradation resistance of the Cr₃C₂–NiCr coating, which might be attributed to the rapid growth of oxide scale on the coating surface, which blocks the penetration of corroding species. Furthermore, the addition of CeO₂ also retards the diffusion between substrate and coating. [ABSTRACT FROM AUTHOR]