Abstract
The oxidation behavior of Cr- and Si- bearing ferritic stainless steels has been studied in the O2+H2O+Ar mixed atmospheres at 600°C, in an attempt to differentiate the effect of O2 and H2O on the occurrence and growth of nodular scale and to clarify the effect of Cr and Si contents on the oxidation resistance. In the results, the reddish brown scale grew on the SUS 430 steel in above 10% H2O containing atmosphere regardless of O2 concentration. On 11%Cr-2%Si steel, the reddish brown scale developed in the above 15% H2O and under 10% O2 mixed Ar atmospheres. On the other hand, 18%Cr-2.5%Si steel showed good resistance to reddish brown scale in all conditions examined. It has been observed that O2 promotes the formation of Cr-enriched M2O3 type scale suppressing the nodular scale formation. However, once nodular scale is formed, O2 accelerates its growth. While, it has been found that H2O promotes the formation of M3O4 type scale and causes nodular scale.
