HIGH-TEMPERATURE OXIDATION OF HOT-DIP ALUMINIZED P23 STEEL

摘要

ASTM P23 steel (Fe-2.25Cr-1.6W-0.1Mo in wt.%) was hot-dip aluminized and oxidized at 800 degrees C and 1000 degrees 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 alpha-Al(2)O(3 )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)/(Al13Fe4 layer) to either (thin alpha-Al2O3 scale)/(Al5Fe2 layer)/(AlFe layer)/(AlFe3 layer)/ (alpha-Fe (Al) layer) at 800 degrees C or (thick alpha-Al2O3 scale)/(AlFe3 layer)/ (alpha-Fe(Al) layer) at 1000 degrees C. At 1000 degrees C, Fe2O3 was also formed in addition to alpha-Al2O3 scale, due to the enhanced outward diffusion of Fe, thus suppressing the formation of cracks in the coating.