| Summary: | The phase formation-transition process and microstructure evolution of Fe–3%Si steel oxide layers were systematically studied during the high-temperature oxidation process with oxidizing atmosphere when annealed at 1000–1240 °C for 200 min. The micromorphology, oxidation mechanism and crystal structure stability were characterized and discussed combining with the XRD, FESEM and XPS technology. The oxidized scale shows more and more complex multiple layers structure including single layer, double layers and three layers with the increasing of annealing temperature, which attributes to the diffusion effect and oxidation reaction oxygen anions and metal cations. The formation of SiO2, FeO and Fe2SiO4 layer also could inhibit the oxidation reaction of matrix. The oxidized scale mainly shows a single layer structure of Fe2O3 when annealed at 1000–1080 °C, which is easy to peel off from matrix. It shows a double oxide layers structure when annealed at 1080–1120 °C, the loose outer layer contains Fe2O3, and the grid inner layer contain SiO2, FeO and Fe2SiO4 compounds. It shows an outermost, intermediate and inner three layers structure when annealed at 1160–1240 °C. The outermost layer is Fe2O3, the main phases of intermediate layer are FeO and Fe2SiO4 compounds as well as some SiO2 particles, and the inner layer (joint layer) is SiO2.
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