The isothermal oxidation kinetics of a Co-40Cr alloy and its yttrium ion-implanted samples were studied at 1000℃ in air by thermal-gravity analysis （TGA）. Scanning electronic microscopy （SEM） was used to examine ...The isothermal oxidation kinetics of a Co-40Cr alloy and its yttrium ion-implanted samples were studied at 1000℃ in air by thermal-gravity analysis （TGA）. Scanning electronic microscopy （SEM） was used to examine the Cr203 oxide film＇s morphology after oxidation. An acoustic emission （AE） method was used in situ to monitor the cracking and spalling of oxide films formed on samples during oxidation and subsequent aircooling stages. A theoretical model was proposed relating to the film fracture process and was used to analyze the acoustic emission spectrum on time domain and the AE-event number domain. It was found that yttrium implantation remarkably reduced the isothermal oxidation rate of Co-40Cr and improved the anti-cracking and anti-spalling properties of Cr2O3 oxide film. The reasons for the improvement were mainly that the implanted yttrium reduced the grain size of Cr2O3 oxide, increased the high temperature plasticity of oxide film, and remarkably reduced the number and size of Cr203/Co-40Cr interfacial defects.展开更多
The isothermal and cyclic oxidizing kinetics of Co-40Cr alloy and its yttrium ion-implanted samples were studied at 1000℃ in air by thermal-gravity analysis （TGA）. Scanning electronic microscopy （SEM） was used to...The isothermal and cyclic oxidizing kinetics of Co-40Cr alloy and its yttrium ion-implanted samples were studied at 1000℃ in air by thermal-gravity analysis （TGA）. Scanning electronic microscopy （SEM） was used to examine the Cr203 oxide film＇s morphology after oxidation. Secondary ion mass spectroscopy （SIMS） method was used to examine the binding energy change of chromium caused by yttrium doping. Acoustic emission （AE） method was used in situ to monitor the cracking and spalling of oxide films formed on both samples during oxidizing and subsequent air-cooling stages. It is found that yttrium implantation remarkably reduces the isothermal oxidizing rate of Co-40Cr and improves the anti-cracking and anti-spalling properties of Cr2O3 oxide film. The reasons for the improvements are mainly that implanted yttrium reduces the grain size of Cr2O3 oxide, increases the high temperature plasticity of oxide film, and remarkably reduces the number and size of Cr2O3/Co-40Cr interfacial defects.展开更多
Isothermal and cyclic oxidation behaviors of chromium samples with and without nanometric CeO2 coating were studied at 900℃ in air. Scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and ...Isothermal and cyclic oxidation behaviors of chromium samples with and without nanometric CeO2 coating were studied at 900℃ in air. Scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and high-resolution electron microscopy （HREM） were used to examine the morphology and microstructure of the oxide film. It was found that ceria coating greatly improved the oxidation resistance 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 film, and AE signals were analyzed in time-domain and number-domain according to related oxide fracture model. Laser Raman spectrometer was also used to study the stress of oxide film formed on Cr with and without ceria. The improvement in oxidation resistance of chromium is believed mainly due to that ceria greatly reduced the growth speed and grain size of Cr2O3. This fine grained Cr2O3 oxide film might have better high temperature plasticity and could relieve parts of the compressive stress by means of creeping and maintained ridge character and relatively lower level of internal stress. Meanwhile, ceria application reduced the size and number of interfacial defects, remarkably enhanced the adhesive property of Cr2O3 oxide scale formed on Cr substrate.展开更多
The isothermal oxidizing kinetics of Co-40Cr alloy and its yttrium ion-implanted samples are studied at 1 000 ℃ in air by thermal-gravity analysis （TGA）. Scanning electronic microscopy （SEM） is used to examine th...The isothermal oxidizing kinetics of Co-40Cr alloy and its yttrium ion-implanted samples are studied at 1 000 ℃ in air by thermal-gravity analysis （TGA）. Scanning electronic microscopy （SEM） is used to examine the Cr2O3 oxide film＇s morphology after oxidation. Acoustic emission （AE） method is used in situ for monitoring the cracking and spalling of oxide films formed on both samples during oxidizing and subsequent air-cooling stages. Theoretical model is proposed relating to the film fracture process and is used for analyzing the acoustic emission spectrum both on time domain and on AE-event number domain. It is found that yttrium implantation remarkably reduces the isothermal oxidizing rate of Co-40Cr and improves the anti-cracking and anti-spalling properties of Cr2O3 oxide film. The reasons for the improvement are mainly that the implanted yttrium reduced the grain size of Cr2O3 oxide, increased the high temperature plasticity of oxide film, and remarkably reduced the number and size of Cr2O3/Co-40Cr inteffacial defects.展开更多
基金The Natural Science Foundation of Higher EducationInstitutions of Jiangsu Province (No.04KJB510073).
文摘The isothermal oxidation kinetics of a Co-40Cr alloy and its yttrium ion-implanted samples were studied at 1000℃ in air by thermal-gravity analysis （TGA）. Scanning electronic microscopy （SEM） was used to examine the Cr203 oxide film＇s morphology after oxidation. An acoustic emission （AE） method was used in situ to monitor the cracking and spalling of oxide films formed on samples during oxidation and subsequent aircooling stages. A theoretical model was proposed relating to the film fracture process and was used to analyze the acoustic emission spectrum on time domain and the AE-event number domain. It was found that yttrium implantation remarkably reduced the isothermal oxidation rate of Co-40Cr and improved the anti-cracking and anti-spalling properties of Cr2O3 oxide film. The reasons for the improvement were mainly that the implanted yttrium reduced the grain size of Cr2O3 oxide, increased the high temperature plasticity of oxide film, and remarkably reduced the number and size of Cr203/Co-40Cr interfacial defects.
基金the National Natural Science Foundation of China(No.59231011)Natural Science Foundation of Jiangsu Province(No.JK0410184)
文摘The isothermal and cyclic oxidizing kinetics of Co-40Cr alloy and its yttrium ion-implanted samples were studied at 1000℃ in air by thermal-gravity analysis （TGA）. Scanning electronic microscopy （SEM） was used to examine the Cr203 oxide film＇s morphology after oxidation. Secondary ion mass spectroscopy （SIMS） method was used to examine the binding energy change of chromium caused by yttrium doping. Acoustic emission （AE） method was used in situ to monitor the cracking and spalling of oxide films formed on both samples during oxidizing and subsequent air-cooling stages. It is found that yttrium implantation remarkably reduces the isothermal oxidizing rate of Co-40Cr and improves the anti-cracking and anti-spalling properties of Cr2O3 oxide film. The reasons for the improvements are mainly that implanted yttrium reduces the grain size of Cr2O3 oxide, increases the high temperature plasticity of oxide film, and remarkably reduces the number and size of Cr2O3/Co-40Cr interfacial defects.
基金Project supported by the National Natural Science Foundation of China (29231011)the Natural Science Foundation ofJiangsu Province (04KJD460010)
文摘Isothermal and cyclic oxidation behaviors of chromium samples with and without nanometric CeO2 coating were studied at 900℃ in air. Scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and high-resolution electron microscopy （HREM） were used to examine the morphology and microstructure of the oxide film. It was found that ceria coating greatly improved the oxidation resistance 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 film, and AE signals were analyzed in time-domain and number-domain according to related oxide fracture model. Laser Raman spectrometer was also used to study the stress of oxide film formed on Cr with and without ceria. The improvement in oxidation resistance of chromium is believed mainly due to that ceria greatly reduced the growth speed and grain size of Cr2O3. This fine grained Cr2O3 oxide film might have better high temperature plasticity and could relieve parts of the compressive stress by means of creeping and maintained ridge character and relatively lower level of internal stress. Meanwhile, ceria application reduced the size and number of interfacial defects, remarkably enhanced the adhesive property of Cr2O3 oxide scale formed on Cr substrate.
基金National Natural Science Foundation of China(No.29231011)Natural Science Foundation of Jiangsu Province,China(No.07KJD430246)
文摘The isothermal oxidizing kinetics of Co-40Cr alloy and its yttrium ion-implanted samples are studied at 1 000 ℃ in air by thermal-gravity analysis （TGA）. Scanning electronic microscopy （SEM） is used to examine the Cr2O3 oxide film＇s morphology after oxidation. Acoustic emission （AE） method is used in situ for monitoring the cracking and spalling of oxide films formed on both samples during oxidizing and subsequent air-cooling stages. Theoretical model is proposed relating to the film fracture process and is used for analyzing the acoustic emission spectrum both on time domain and on AE-event number domain. It is found that yttrium implantation remarkably reduces the isothermal oxidizing rate of Co-40Cr and improves the anti-cracking and anti-spalling properties of Cr2O3 oxide film. The reasons for the improvement are mainly that the implanted yttrium reduced the grain size of Cr2O3 oxide, increased the high temperature plasticity of oxide film, and remarkably reduced the number and size of Cr2O3/Co-40Cr inteffacial defects.
