ISOTHERMAL OXIDATION BEHAVIOUR STUDY OF Fe-14Ni-9AL-7,5Cr-5Mo ALLOY AT 800, 900, AND 1000°C

• Main Author: XAVIER TALA (NIM : 12514003), SJIOEN
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/31014
• Institution: Institut Teknologi Bandung

Nowadays, demand for cleaner and more efficient electrical energy had led human <br /> <br /> to search and find a new alloy that can fulfill better technical and economical <br /> <br /> requirements. Increasing efficiency had strong correlation to operation temperature <br /> <br /> of a power plant. One of the metal alloy that was being developed that had good <br /> <br /> prospect is advanced ferritic steel system of Fe-Ni-Al-Cr-Mo. Specifically, Fe- <br /> <br /> 14Ni-9Al-7,5Cr-5Mo alloy had been researched and showed has lower coarsening <br /> <br /> rate with the precipitate strengthening mechanism B2 – (Fe,Ni)Al. Nevertheless, <br /> <br /> there was no information about this alloy’s behaviour in high temperature <br /> <br /> oxidation. Isothermal oxidation behaviour study was conducted to determine high <br /> <br /> temperature oxidation resistance of this alloy. <br /> <br /> To study the isothermal oxidation behaviour of Fe-14Ni-9Al-7,5Cr-5Mo alloy, <br /> <br /> series of isothermal oxidation experiment had been conducted at 800, 900, and <br /> <br /> 1000°C for 1, 10, 50, and 150 hours. Fe-14Ni-9Al-7,5Cr-5Mo alloy was melted <br /> <br /> using Mini-DC-EAF and produced speciment button-shaped. These speciments <br /> <br /> were homogenized for 24 hours at 1100°C. Furtherly, the alloy was cut and polished <br /> <br /> using abrasive SiC paper with 240, 400, 800, 1200, and 2000 mesh grit. Then, the <br /> <br /> speciment was oxidized with according to and temperature variation combinations. <br /> <br /> There were 12 combinations examined in this experiment. The last step of this <br /> <br /> experiment was characterization of the speciment using OM (optical microscope), <br /> <br /> SEM-EDS (scanning electron microscope-energy dispersive spectroscopy), and <br /> <br /> XRD (X-ray diffraction). <br /> <br /> Based on the research results, Fe-14Ni-9Al-7,5Cr-5Mo alloy which is oxidized at <br /> <br /> 800°C follows parabolic oxidation kinetics law where kp (parabolic constant) is 1,61 <br /> <br /> x 10-7 gr2/cm4 hour. This result indicates that the addition of Mo will decrease the <br /> <br /> alloy oxidation resistance eight time lower than alloy without Mo addition. <br /> <br /> Whereas, the speciments that are tested at temperature 900 and 1000°C have no <br /> <br /> correlation with any kinetics law. Moreover, spherical-cluster oxide morphology is <br /> <br /> found on the speciment that is oxidized at 800°C for 150 hours. Needle-shaped <br /> <br /> morphology is found on the speciment that is oxidized at 900°C for 150 hours. <br /> <br /> Meanwhile, polygonal plate oxide cluster morphology is found on the speciment <br /> <br /> that is oxidized at 1000°C for 150 hours. Generally, the oxides formed in this <br /> <br /> experiment are Fe2O3, Fe3O4, FeO, Al2O3, Cr2O3, MoO3, and Cr2NiO4.