Effect of Silicon on High Temperature Oxidation Of Stainless Steels★

Abstract

Abstract Growth of oxide films at 600 and 800 C on a series of 16 Cr-10 Ni-bal Fe stainless steels with silicon contents ranging from 0.17 to 3.55 percent was studied by electron microscopy, electron diffraction, X-ray diffraction and X-ray fluorescence analysis techniques. Oxide scales and sub-scales formed during oxidation at 1000 C were studied optically in cross section as well as by X-ray diffraction and fluorescence analysis. Results show that as silicon content increases oxidation resistance increases rapidly until at the high silicon level, 3.55 percent, a very thin oxide film is formed at 60u and 800 G and very little oxide scale forms at 1000 C. Mechanism of oxidation resistance imparted by silicon appears to be that it decreases the number of defects in the initial oxide films formed at the metal-oxide interface. With a lesser number of defects in the thin film, an enrichment of Cr at the metal-oxide interface and in the oxide films occurs and the rate of diffusion of iron outward to form the oxide scale is greatly retarded. 2.3.7