Influence of nano-ceria sol-gel coating on oxidation behavior of chromium at 1000 °C

Isothermal oxidation behavior of chromium with and without nanon sol-gel CeO2 coating is studied at 1000 °C in air. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are used to examine the surface morphology and microstructure of the oxide films. It is found that ceria coating greatly improves the anti-oxidation property of chromium. Laser Raman spectrometer and X-ray diffraction spectrometer (XRD) are also used to study the stress level in oxide films formed on ceria-coated and ceria-free Cr. Secondary ion mass spectrometer (SIMS) is used to examine Cr, O and Ce element distribution in depth in oxide films. Results show that nano-ceria application greatly reduces the growth speed and grain size of Cr2O3 film, and this fine grained Cr2O3 film probably has better high temperature plasticity, i.e., oxide film relieves part of the compressive stress by means of creeping. Meanwhile, CeO2 changes the oxide film growth mechanism from predominant cation outward diffusion to anion inward diffusion. XRD and Raman testing results both show the stress declination effect due to nano-CeO2 application, and their discrepancy in the rare earth effect is analyzed.