THE ISOTHERMAL OXIDATION OF TERNARY FE-22NI-20AL ALLOYS AT 600, 700, AND 800OC

• Main Author: Utami, Lidyana
• Format: Final Project
• Language: Indonesia
• Subjects: Metalurgi
• Online Access: https://digilib.itb.ac.id/gdl/view/52063
• Institution: Institut Teknologi Bandung

The demand of world’s electricity rises along with the increase of population, level of economy, industry and technological development. Indonesian government plans to increase electrical capacity as much as 35000 Megawatts in the next 5(five) years whereby 60% of which shall be in the form of steam power plants. In the year 2010, average efficiency of world’s steam power plants was around 33%. Improvement on efficiency continues to be made where one of which is to increase the operating temperature of the power plants. Fe-Ni-Al constitutes as metal alloy with duplex structure to be developed as an alternative to nickelbased superalloy due to its density and of its lower price. Intermetallic alloy of Fe-Ni-Al has duplex microstructure that comprises of ordered B2 or ?' (mainly of Ni Al) and that of disordered FCC or ? (generally of Fe) which provides a combination of high temperature ductility, creep resistance at temperatures above 600-700oC, and the high Al content also provides resistance to oxidation and corrosion. A series of experiments has been conducted to study the isothermal oxidation resistance in Fe-20Ni-21Al alloys at temperatures of 600, 700 and 800oC. The tests were carried out on a tanur tabung horizontal with testing times applied to it were 1, 10, 50, and 150 hours. After the test, then the data of mass change alloys were calculated. In this experiment, the alloys is also characterized by prior to and post tests. The tools used to characterize the alloys in these experiments are optical microscope, X-ray Diffractometer, and Scanning Electron Microscope - Energy Dispersive Spectroscopy (SEM-EDS). From the results of characterization, analysis on the microstructure, the oxide layers and their depths shall then be conducted. The result shows that higher of temperature affects faster oxidation reaction. The increasing the oxidation time affects lower oxidation rate gradient of time. It also formed ?-Al2O3, ?- Al2O3, ? - Al2O3, ? - Al2O3, and amorf alumina, Fe2O3, Fe3O4, wustite, NiO Al2NiO4, Al2FeO4, AlFeO3, with the main scale is Al2O3. Oxidation rate of Fe-22Ni-20Al alloy at 600oC and 700oC follow oxidation rate equation by y2 = 0.0289t + 0.4527 and y2 = 0.0231t + 1.4542 respectivly and at 800oC follow logarithmic rate equation by y = 1.2313 log (t + 1) + 0.5119.