SIMS/XPS characterization of surface layers formed in 3 mass% Si-steel by annealing in oxygen at low partial pressure

Selective oxidation in silicon steel shows several interesting phenomena, such as the formation of an internal oxidation zone that depends on the oxidation conditions and the steel composition. In this work, SIMS and XPS were used for characterizing the formation processes of surface layers formed during selective oxidation of a typical silicon steel. The starting material is a secondary-recrystallized 3 mass% Si-steel sheet with a surface orientation of (011). Sample sheets were annealed at a temperature of 948-1023 K under an atmosphere with a low partial pressure of oxygen. The SIMS depth profiles show that the internal oxidation zone thickens and an iron-rich layer that formed on the internal oxidation zone expands as the annealing temperature increases. Manganese and chromium levels increase outside the internal oxidation zone, whereas tin exists in the internal oxidation zone. The XPS results of the sample surface show that silicon and manganese levels increase on the sample surface to form oxides, and the chemical composition and state of these elements depend on the annealing temperature. In addition, tin increases on the surface of a relatively thick iron-rich layer that formed on the internal oxidation layer. These experimental results are discussed on the basis of the thermodynamic characteristics of the elements. Copyright (C) 2003 John Wiley Sons, Ltd.