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High Temperature Isothermal Oxidation at 950°C of Ni-based Fe-40Ni-24Cr Alloy

Anuar Aqmar Ikhmal, Parimin Noraziana, Ahad Nor Azwin, Derman Mohd Nazree, Garus Sebastian, Vizureanu Petrica

Archives of Metallurgy and Materials

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2024

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Vol. 69, iss. 3

1191--1198

EN

The effect of different heat treatment temperatures on the isothermal oxidation of Ni-based Fe-40Ni-24Cr alloy was studied. The alloy underwent a heat treatment process at 1000°C and 1200°C for 3 hours of soaking time, followed by water quenching. These samples are labeled as N10 and N12. The heat-treated samples were characterized in terms of grain size using an optical microscope and hardness testing using a Rockwell hardness. As a result, increasing the heat treatment temperature increases the average grain size of the alloy and lowers the hardness value. Heat-treated N10 and N12 samples were subjected to an isothermal oxidation test at 950°C for an exposure time of 150 h. Oxidized heat-treated samples were characterized in terms of oxidation kinetics calculated based on weight change per surface area as a function of time. In addition, phase analysis and oxide surface morphology were measured using x-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. As a result, the oxidation kinetics of both samples showed a pattern of weight gain with N10 recording the lowest weight gain. Both samples obey a parabolic rate law, indicating a controlled oxide growth rate. N10 recorded the lowest parabolic rate constant of 2.5×10-8 mg2cm-4s-1, indicating a low oxidation rate, thus having good oxidation resistance. Phase analysis using XRD shows that several oxide phases have been formed consisting of Cr-containing oxides Cr2O3 and MnCr2O4. In addition, SEM analysis displayed a uniform oxide layer formed on the N10 sample, indicating good oxide adhesion. This finding shows an important contribution to the oxidation protection mechanism that records the fine grain obtained from the heat treatment process can increase good oxidation resistance.

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Effect of Heat Treatment Temperature on Isothermal Oxidation of Ni-based Fe-33Ni-19Cr Alloy

Zaiton Nurul Athirah Z., Parimin Noraziana, Hayazi Nur Farhana, Zainal Farah Farhana, Garus Sebastian, Vizureanu Petrica

Archives of Metallurgy and Materials

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2024

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Vol. 69, iss. 2

747--752

EN

This project studies the influence of different grain sizes of Ni-based Fe-33Ni-19Cr alloy obtained from heat treatment procedure on high temperature isothermal oxidation. Heat treatment procedure was carried out at two different temperatures, namely 1000℃ and 1200℃ for 3 hours of soaking time, followed by quenching in the water. These samples are denoted as T1000 and T1200. The heat-treated Ni-based Fe-33Ni-19Cr alloy was subjected to an isothermal oxidation test at 950℃ for 150 hours exposure. Oxidized heat-treated alloys were tested in terms of oxidation kinetics, phase analysis and surface morphology of oxidized samples. Oxidation kinetics were determine based on weight change per surface area as a function of exposure time. Phase analysis was determined using the x-ray diffraction (XRD) technique and surface morphology of oxidized samples was characterized using a scanning electron microscope (SEM). As a result, the heat treatment procedure shows varying grain sizes. The higher the heat treatment temperature, shows an increase in grain size with a decrease in hardness value. The oxidation kinetics for both heat-treated samples showed an increment pattern of weight change and followed a parabolic rate law. The oxidized T1000 sample recorded the lowest parabolic rate constant of 3.12×10-8mg2cm-4s-1, indicating a low oxidation rate, thus having good oxidation resistance. Phase analysis from the XRD technique recorded several oxide phases consisting of Cr2O3, MnCr2O4, and (Ti0.97Cr0.03)O2 oxide phases. In addition, a uniform oxide layer is formed on the oxidized T1000 sample, indicating good oxide scale adhesion, thereby improving the protective oxide behavior.

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Investigation of Corrosion Behaviour of Mild Steel Embedded in Geopolymer Paste with Curing and Non-Curing Process

Shaharudin Fatin Shahira, Zainal Farah Farhana, Hayazi Nur Farhana, Parimin Noraziana, Nadzri Nur Izzati Muhammad, Hastuty Sri, Kusbiantoro Andri

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 4

1603--1607

EN

This research was conducted to examine the corrosion behaviour of mild steel bar embedded in geopolymer paste based fly ash Class F during curing and non-curing process. The geopolymer paste was fabricated by blending in the fly ash with alkaline activators (NaOH solution with molarity of 12 M, 2.5 ratio of solution Na2SiO3/NaOH). The paste was produced in 50 mm × 50 mm × 50 mm mould where the mild steel bar of 100 mm (length) × 12 mm (diameter) was embedded at the center of geopolymer paste. This is to comprehend the corrosion behaviour of mild steel embedded in geopolymer paste with and without curing process. Process of curing is carried out for 24 hours at a temperature of 60°C in oven. While on the contrary, the non-curing process will only be leave at room temperature. Both samples were tested after 28 days of curing to determine the corrosion behaviour, phase analysis and morphology analysis. In accordance with the morphology analysis, it shows that the fly ash was totally reacted with alkaline solutions in curing geopolymer paste sample while the non-curing geopolymer paste has shown the unreacted fly ash with high number of pores. The phase analysis of mild steel embedded in this geopolymer paste during curing and without curing process has proven that the presence of new crystallographic peak which also known as passive layer occurred. The potential values result by OCP testing shows the curing sample has highest potential values as compared to the non-curing sample ones.