MICROSTRUCTURAL STABILITY AND HIGH-TEMPERATURE ISOTHERMAL OXIDATION BEHAVIOUR STUDIES OF AS-HOMOGENIZED AL0.5COCRFENI HIGH ENTROPY ALLOY
Based on the law of thermodynamics, the efficiency of heating engines such as rocket nozzles, nuclear reactor system, aircraft gas turbine, and concentrated solar power can be increased by increasing the operating temperature. However, as the temperature rises, the component of the machines tends to...
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| Format: | Final Project |
| Language: | Indonesia |
| Online Access: | https://digilib.itb.ac.id/gdl/view/74213 |
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| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | Based on the law of thermodynamics, the efficiency of heating engines such as rocket nozzles, nuclear reactor system, aircraft gas turbine, and concentrated solar power can be increased by increasing the operating temperature. However, as the temperature rises, the component of the machines tends to be degraded due to interaction with surrounding environment, one of them was the degradation by oxidation. Superalloy have been developed for high temperature applications, but the applicability was limited by their melting point. One of the candidates to replace these alloys is Al-Co-Cr-Fe-Ni high entropy alloy due to its high melting point, better microstructural stability, and its ability to form protective oxide scale on its surface. In this research, the isothermal oxidation of the homogenized Al0.5CoCrFeNi alloy were studied at 900?, 1000?, 1100?.
A series of experiments were conducted to study the stability and oxidation behaviour of Al0.5CoCrFeNi alloy at high temperatures. The experiment was started by melting iron, nickel, cobalt, aluminium, chromium with high purity using mini-DC-EAF and continued by homogenization using horizontal tube furnace in inert atmosphere. The isothermal oxidation test of the alloy were conducted at temperatures of 900?, 1000?, and 1100? for 2, 16, and 40 hours. The oxidation specimens were characterized by using X-Ray Diffraction, Scanning Electron Microscope- Energy Dispersive Microscopy, Optical Microscope, and micro-Vickers hardness tester machine.
Based on the experiment data, at high temperatures the homogenized Al0.5CoCrFeNi alloy tends to form Fe2O3, Co3O4, spinel of Cr2NiO4, Cr2O3, Al2O3 oxide layer and AlN precipitate. It is concluded that the oxidation mechanism of the alloy is relatively similar with oxidation behaviour of M-Cr-Al alloy (M=Fe, Ni, Al). The oxidation kinetics of the alloy follow parabolic law with activation energy of 202.1 kJ/mol. The B2 phase present at the microstructures tend to shrink and spheroidize at high temperature due to thermal stress on A1/B2 phase interface, thus decreasing hardness of the alloy. |
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