Browsing by Author "Abdullah, T. K"

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    Characterization of molybdenum-modified aluminide coating on 304 stainless steel via slurry
    (Published by EDP science, 2026-05-30) AMBALI IBRAHIM OWOLABI; Anasyida A. S; Abdullah, T. K; AbdulRazak, K; Dhindaw., B. K; Shuaib-Babata, Y. L
    This study investigates the microstructural changes and growth kinetics of intermetallic compounds in Mo-modified aluminide coatings on 304 stainless steels with varying temperatures and times. Molybdenum and alumina were introduced via slurry aluminizing. Heat treatments were conducted at 750 °C, 800 °C, and 850 °C for varying times (6, 8, and 10 h). Aluminide coating was characterized with SEM, EDX, and XRD, revealed the presence of multilayer phases comprising of Fe-Al and Mo-Al intermetallic compounds, along with an alumina scale on the coating surface. Samples heated at 750 °C showed uniform coatings, while those at 800 °C and 850 °C exhibited voids and cracks. The growth kinetics of the coating obey a parabolic law conforming to diffusion-controlled growth. The activation energies calculated for FeAl and Fe3Al were 360 kJ/mol and 237 kJ/mol, respectively, which is higher than that of coatings containing aluminium (FeAl layer: 180 kJ/mol and and Fe3Al layer: 260 kJ/mol). The total activation energy (Q) was 26 kJ/mol for coatings containing molybdenum and 53 kJ/mol for coatings with only aluminium. Hardness of the intermetallic layers varied from 378 to 966 HV for Mo-modified coatings as compared to aluminide coating (380 to 1030 Hv). The corrosion behaviour of Mo-aluminide coatings was investigated in 3.5% NaCl using polarization and electrochemical impedance spectroscopy (EIS) tests. Results show improved performance of corrosion resistance due to Mo-rich intermetallic phases, with the 6 h sample exhibiting the best corrosion resistance.
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    Formation and Growth Kinetic of Intermetallic Layers on 304SS at Different Slurry Aluminizing Temperature and Time Using Si‑Al2O3‑Modified Aluminide Coating
    (Published by springer, 2025-05-18) AMBALI IBRAHIM OWOLABI; Anasyida, A. S; Abdullah, T. K; Dhindaw B. K
    The study explored how the presence of silicon (Si) and alumina influences the microstructures and growth kinetics of intermetallic compounds within aluminide coatings applied to 304 stainless steels. The aluminide coating was prepared via slurry aluminizing techniques and heat treated at 700 °C, 800 °C and 850 °C for 6, 8 and 10 h. The aluminide coating was characterized using field emission electron microscope-energy dispersive X-ray, X-ray diffraction and hardness. Multilayer phases were formed which comprise of binary phases ( Fe2Al5, FeAl3, FeAl and Fe3Al), and the Fe–Si–Al ternary phases ( Fe2Al3Si3, Fe4Al17.5Si1.5 and Fe4Al1.7Si). As the aluminizing temperature and time increase, the thickness of the brittle intermetallic layer ( Fe2Al5) layer decreases, while the thickness of the ductile intermetallic layers (FeAl and Fe3Al) increases. The growth rate of the layers obeyed a parabolic law. The activation energy for Fe2Al5 was − 174 kJ/mol, while the activation energy for FeAl and Fe3Al were 72 kJ/mol and 155 kJ/mol respectively. Microhardness measurement revealed that Fe2Al5, FeAl, and Fe3Al layers had hardness values of 880– 1010 HV, 570–630 HV, and 320–410 HV respectively at all aluminizing temperature and time. Fe2Al5 has the lowest toughness and the hardest zone in the aluminide coating. The Si addition effectively reduced the coating thickness of the brittle intermetallic layers and aided the growth of ductile intermetallic layers.