Investigation on short term water vapour oxidation of Super304H

Abstract

The short time oxidation behaviour of Super304H was studied at 700°C for different periods. The structure and composition of the oxide layers were investigated using line scanning of scanning electron microscopy equipped with energy dispersive spectroscopy (EDS). In the sample oxidised for 4 h, a double layer scale consisting of outer magnetite layer and inner chromium rich iron oxide was observed from the cross-section. The EDS results from oxide layer surfaces of other three samples showed that no obvious outer layer can be observed after 3 h oxidation. The oxide phases have been identified by X-ray diffraction and Raman spectrum. Atomic force microscopy was used to reveal the mechanism of early oxidation stage of Super304H on samples oxidised for 1·5, 2 and 3 h, respectively. The roughness of the layer surface increased with increasing oxidation time in the early stage, which is in accordance with the proposed model and indicates that the columnar nickel oxide in the specimen is connected to the formation of chromium oxide.