Effect of Si Addition on Oxidation Behavior of Nb Containing Ferritic Stainless Steel

摘要

The effect of Si on the oxidation resistance of high purity Nb containing 19% Cr ferritic stainless steels has been investigated by means of isothermal heating at temperatures up to 1273 K in air and, the structures of the scale and scale/metal interface were investigated with FE-SEM and FE-TEM. The results are as follows:Si improved the oxidation resistance, as reported in previous studies. The Si addition of about 0.1% improved the limit temperature of the oxidation resistance more than 100 K. The presence of an amorphous SiO_(2) layer was found in the interface between the Cr_(2)O_(3) scale and the metal. This layer might act as an oxidation resistance barrier. In the Si-free steel, a NbO_(2) layer formed under the Cr_(2)O_(3) scale, and the Fe_(2)Nb- free region formed beneath the surface. On the other hand, when Si was added, the formation of NbO_(2) layer was suppressed. In case of 1%Si, no NbO_(2) layer formed and the Fe_(2)Nb-free region was eliminated. In addition, Fe particles were present in the Cr_(2)O_(3) scale in the Si-added steel.