| A study has been made to investigate the effects of silicon(Si) addition on the oxidation properties of Fe-14Cr-1Al ferritic stainless steels at 1173K. Four steels containing different amount of Si (0.5, 1, 2, 5 wt% Si) were arc melted and homogenized at 1473K for 24 hours and oxidized at 1173K. Both the isothermal and cyclic oxidation tests revealed that the addition of Si increased the oxidation resistance of Fe-14Cr-1Al alloy. With 0.5w%Si, Cr oxide was formed as surface oxide, and Si, Al oxides were formed internally below Cr oxide layer. With 1w%Si, Al oxide was mixed with Cr oxides on the surface. However, with Si content higher than 2w%, a stable Al₂O₃ layer was formed rapidly. From theoretical evaluation using ChemSage^(TM) program, the Al activity in Fe-Al-5Si steel is about 5 times higher than that in Fe-1Al alloy at 1173K, which is the most probable reason for the rapid formation of Al oxide in the high Si steels. |
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