Abstract
Isothermal and cyclic oxidation behavior of chromium and its superficially applied nanometric CeO2 samples were studied at 900°C in air. Scanning electronic microscopy, (SEM), transmission electronic microscopy (TEM) and high resolution electronic microscopy (HREM) were used to examine the morphology and micro-structure of oxide films. It was found that ceria addition greatly improved the anti-oxidation ability of Cr both in isothermal and cyclic oxidizing experiments. Acoustic emission (AE) technique was used in situ to monitor the cracking and spalling of oxide films, and AE signals were analyzed in time-domain and number-domain according to the related oxide fracture model. Laser Raman spectrometer was also used to study the stress status of oxide films formed on Cr with and without ceria. The main reason for the improvement in anti-oxidation of chromium was that ceria greatly reduced the growing speed and grain size of Cr2O3. This fine-grained Cr2O3 oxide film might have better high temperature plasticity and could relieve parts of compressive stress by means of creeping, and maintained the ridge character and relatively low internal stress level. Meanwhile, ceria application reduced the size and the number of interfacial defects, while remarkably enhanced the adhesive property of Cr2O3 oxide scale formed on Cr substrate.
Supported by National Natural Science Foundation of China (Grant No. 29231011) and Natural Science Foundation of Jiangsu Province (Grant No. 04KJD460010)
Supported by National Natural Science Foundation of China (Grant No. 29231011) and Natural Science Foundation of Jiangsu Province (Grant No. 04KJD460010)
Notes
Supported by National Natural Science Foundation of China (Grant No. 29231011) and Natural Science Foundation of Jiangsu Province (Grant No. 04KJD460010)