High temperature oxidation of silicon and copper–silicon containing steels

Abstract

The isothermal oxidation behaviour of silicon and copper containing steels was studied under laboratory dry air conditions at temperatures from 950 to 1180°C. The oxidation kinetics was determined by gravimetric means and followed by parabolic relationships at all temperatures for both steels. Characterisation of the oxide scales comprised X-ray diffraction, light optical microscopy and SEM including EDX analysis. It was found that the oxide microstructure depended on the silicon and copper contents in the alloys. For the copper containing steel oxidised at 950°C, enrichment of this element was not appreciated at the metal/oxide interface or across the oxide scale, a situation that changed at 1100°C where copper enrichment was localised next to the steel substrate. The specimens oxidised at 1180°C revealed that copper enrichment was located at the surface of the specimens. The effect of the alloying elements on the oxidation rate and the microstructure of the oxides formed on the steels are discussed.