A Microstructural Investigation of Austenitic Heat Resistant Alloy after 500 h of Steam Oxidation.

Alloy 709 was oxidized at 700 °C for 500 h in a steam environment. A microstructural analysis of the oxide scale is reported. Modern techniques of advanced electron microscopy were used to characterize the morphology of the oxide scale and recognize its single components. The material developed a complex, multilayered oxide scale. The outermost layer consisting of Fe2O3. Fe2NiO4 tI28 spinel was detected underneath. An internal oxidation zone is present in the innermost layer. High quality SEM-EDS maps give insight into a larger area of the oxide scale at a relatively low magnification.