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Microstructural Stability and High-Temperature Oxidation Behavior of Al0.25CoCrCuFeNi High Entropy Alloy Muhammad, Fadhli; Lestari, Ernyta Mei; Achmad, Tria Laksana; Korda, Akhmad Ardian; Prawara, Budi; Prajitno, Djoko Hadi; Jihad, Bagus Hayatul; Setianto, Muhamad Hananuputra; Basuki, Eddy Agus
Metalurgi Vol 39, No 1 (2024): Metalurgi Vol. 39 No. 1 2024
Publisher : National Research and Innovation Agency (BRIN)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.55981/metalurgi.2024.745

Abstract

Al0.25CoCrCuFeNi is a high-entropy alloy composed of transition metals, specifically designed for high-temperature applications owing to its favorable mechanical properties, high melting point, and excellent high-temperature resistance. This alloy has been identified as a promising material for space exploration, particularly in the fabrication of combustion chambers and rocket nozzles by the National Aeronautics and Space Agency. Ongoing alloy development involves modifying the elemental composition. This study reduced aluminum content in the equiatomic AlCoCrCuFeNi alloy to Al0.25CoCrCuFeNi, followed by isothermal oxidation treatments at 800, 900, and 1000℃. A series of experiments were conducted to investigate the microstructure stability and oxidation behavior of the Al0.25CoCrCuFeNi alloy. The alloying elements were melted using a single DC electric arc furnace, followed by homogenization at 1100°C for 10 hours in an inert atmosphere. Subsequently, samples were cut into coupons for isothermal oxidation testing at the desired temperatures for 2, 16, 40, and 168 hours. The oxidized samples were characterized using XRD (x-ray diffraction), SEM (scanning electron microscopy) equipped with EDS (energy-dispersive X-ray spectroscopy), optical microscopy, and Vickers hardness testing. The as-homogenized alloy consisted of two constituent phases: an FCC (face-centered cubic) phase in the dendritic region and a copper-rich FCC phase in the inter-dendritic region. The oxides formed during the oxidation process included Al2O3, Cr2O3, Fe3O4, CoO, CuO, NiO, and spinel oxides (Co,Ni,Cu)(Al,Cr,Fe)2O4), with distinct formation mechanisms at each temperature.
High Temperature Oxidation Behavior of ODS Ferritic Stainless Steel Fe-16Cr-4Al-1Ni-0.4Y2O3 Wafda, Hakimul; Prajitno, Djoko Hadi; Basuki, Eddy Agus; Syafiq, Ahmad; Widiawati, Nina; Andi Mustari, Asril Pramutadi
Indonesian Journal of Chemistry Vol 24, No 5 (2024)
Publisher : Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/ijc.95284

Abstract

This study investigates the isothermic oxidation behavior of the new ODS alloy Fe-16Cr-4Al-1Ni-0.4Y2O3 (% by weight) at 700, 800 and 900 °C, with exposure times of 5, 20, 50, and 100 h at each temperature. The purpose is to obtain new data on its high-temperature parabolic oxidation constant for assessing oxidation resistance. The methods used include isothermal oxidation testing, XRD, SEM-EDS characterization, and analysis of oxidation kinetics by monitoring changes in oxide thickness using microscopy and SEM-EDS. The oxide products formed on the sample surface are Fe2O3, Fe3O4, AlFe2O4, and (Fe,Cr)2O3. Al and Cr oxides are located under the dominant Fe oxide layer on the surface of the sample. The oxidation test results showed that the most protective sample was obtained at a temperature of 700 °C for 100 h with an oxide thickness of 263.99 μm. The kinetics analysis correlates strongly with the parabolic equation (R2 ≈ 1). The oxidation rate constants at temperatures of 700, 800, and 900 °C were 681.76, 2957.5, and 12300 μm2 h−1, respectively. The activation energy required by the oxidation reaction in this alloy is 136.5 kJ mol−1. This research enhances understanding and potential applications of the Fe-16Cr-4Al-1Ni-0.4Y2O3 alloy in high-temperature environments.