| Summary: | The modern power generation industry needs materials able to withstand severe conditions, such as high temperatures, steam pressure, and an aggressive environment, to create more electric power out of a decreasing amount of fuel. Therefore, new metallic materials are continuously being developed. In order to gain knowledge about modern materials, the investigation of high Cr and Ni austenitic steel oxidized in 100% steam at 700 °C for 500 h was performed. The morphology, the phase composition, and the chemical composition of the oxidation products were investigated through methods of advanced electron microscopy techniques. Moreover, precipitates present in bulk material were identified. The material developed a continuous and complex oxide scale, consisting of Fe<sub>2</sub>O<sub>3</sub>, Cr<sub>2</sub>O<sub>3,</sub> and spinel phases. Very fine MX, fine ε-Cu, and M<sub>23</sub>C<sub>6</sub> precipitates were found in the bulk material. The creation of iron oxide is induced due to the coarse grain size of the material. Cr<sub>2</sub>O<sub>3</sub> forms due to the internal oxidation process.
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