51314-4209-Characteristics of Oxide Film Formed on Alloy 800 At High Temperature

Available for download

Product Number: 51314-4209-SG

ISBN: 4209 2014 CP

Author: Geogy Abraham

Publication Date: 2014

Member Price: $0.00

Non Member Price: $0.00

Price: $0.00

Qty:

Characteristics of oxide film formed on Alloy 800 at high temperatureGeogy J. Abraham Kushal Singhla and Vivekanand KainMaterials Science Division Bhabha Atomic Research Centre Mumbai – 400 085 India.Department of Metallurgical Engg. PEC University of Technology Chandigarh-160012 India.Abstract:Alloy 800 is used in nuclear industry for steam generator tubing. The stability of oxide film formed on the alloy surface due to its exposure to high temperature and pressure aqueous environment is of paramount importance. The oxide film acts as a barrier for reducing further metal ion dissolution into the environment. Any localized corrosion may result in initiation of stress corrosion cracking. The elemental distribution within the oxide morphology and distribution of the oxide crystallites have a great role to play in determining the stability of oxide films and in preventing initiation of stress corrosion cracking. The present study aims at understanding the effect of cold working and machining on the oxide film formed in high temperature steam. The as-received Alloy 800 specimen and the machined and cold worked specimen were characterized by electron back scattered diffraction (EBSD). Formation of nano-grains on the machined surface was clearly evident. The oxide film morphology was characterized by scanning electron microscopy (SEM) and micro laser Raman technique was used for understanding the distribution and type of oxides formed at 400 °C steam. The formed oxide film was characterized by electrochemical impedance spectroscopy to understand the film characteristics based on resistance capacitance and the defect density. The Raman analysis of the formed oxide films showed broadening of the peaks which was attributed to formation of nano-grains on the machined Alloy 800 and due to stress from the cold working operation. The resistance of the formed oxide film on the as-received and cold worked samples was almost the same indicating that the cold working had not resulted in any major difference in the formed oxide film. In case of machining the oxide film resistance had reduced suggesting a change in the nature of the formed oxide film.