Open Access Conference Proceedings

<div>During hot forming, the formation of oxide layers when heating ferrous materials such as steels can hardly be prevented. On the one hand, the formation of oxides is beneficial, as certain oxide phases can have a lubricating effect. On the other hand, oxide scale leads to a loss of material and the hard and brittle phases lead to forging defects and die wear. In the numerical simulation of hot forging processes, the formation of oxide scale layers on workpieces is currently not considered, as there is no suitable numerical approach to address the scale problem and the material-specific characteristic values are missing. In order to describe the behaviour of oxide scale in finite-element simulations, realistic material data is required. In this work, the basis for the characterisation of oxides shall be established. For this purpose, steel specimens of C45 and C60 were oxidized under controlled conditions at elevated temperatures. Subsequently, the specimens were examined through a scanning electron microscope (SEM) and the individual oxide scale layers consisting of wüstite (FeO), magnetite (Fe3O4) and hematite (Fe2O3) were detected. The specimens were examined using a triboindenter to record the mechanical properties such as nanohardness and modulus of elasticity of each oxide scale component on the nanoscale. XPM (X property mapping) nanohardness mappings were used to visualise the phase transitions and porosity of the oxide scale and compared with the microscopy and SEM images. In addition, magnetite spots in the wüstite oxide layer could be detected through XPM hardness mapping and SEM examinations.</div>

Keywords: Oxide scale layers, C45, C60, Nanoindentation, Scanning electron microscope

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