High-temperature oxidation of sprayed alumina and zirconium‑yttrium-based coatings on Zircaloy-4 in air and oxygen: Investigation on microstructure evolution and phase changes

Zr-Y-C coating was prepared from APS, and its enhancement on the oxidation resistance of Zircaloy-4 in air and oxygen was compared with Al₂O₃ coating. Detailed characterization techniques including SEM, EDS, AFM, Raman spectroscopy and XRD were employed to analyze microstructure evolutions and phase components. Zr-Y-C coating is less susceptible to oxygen and Al₂O₃ coating is more resistant to air attack. Oxides and nitrides were both formed on these two coatings. Air ingress made Zr-Y-C coating exhibit a significant weight gain, while it maintained relatively stable in oxygen. As for Al₂O₃ coating, cracks developed and the porosity increased in air. When exposed to oxygen, metal ion diffusion accelerated, and numerous irregular Zr and Al oxide particles were produced.