Abstract
ASTM P23 steel (Fe-2.25Cr-1.6W-0.1Mo in wt.%) was hot-dip aluminized and oxidized at 800∘C and 1000∘C for 20 h in air in order to determine the effect of aluminizing on the microstructure, hardness, and oxidation resistance of P23 steel. Aluminizing effectively increased the oxidation resistance of P23 steel by forming protective [Formula: see text]-Al2O3 scales. During oxidation, outward diffusion of substrate elements and inward transport of Al and oxygen occurred simultaneously. The oxidation and interdiffusion formed voids in the coating, lowered the microhardness, and transformed the original (Al-rich topcoat)/(Al[Formula: see text]Fe4 layer) to either (thin [Formula: see text]-Al2O3 scale)/(Al5Fe2 layer)/(AlFe layer)/(AlFe3 layer)/([Formula: see text]-Fe(Al) layer) at 800∘C or (thick [Formula: see text]-Al2O3 scale)/(AlFe3 layer)/([Formula: see text]-Fe(Al) layer) at 1000∘C. At 1000∘C, Fe2O3 was also formed in addition to [Formula: see text]-Al2O3 scale, due to the enhanced outward diffusion of Fe, thus suppressing the formation of cracks in the coating.
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