Morphology Analysis of the Scale Formed on Crofer 22APU Steel in Atmospheres Containing SO2

This work presents the results of a morphology analysis of the scale formed on Crofer 22APU steel at high temperature in atmospheres containing SO₂. The studies of steel oxidation were conducted on pre-oxidised and non-pre-oxidised steel within the temperature range of 700?C900 °C in a mixture of air of a varying SO₂ content and in pure air. In the case of oxidation in pure air it was established that on the surface of the Crofer 22APU a two-layer scale is formed. The outer layer of the scale contains MnCr₂O₄, whereas the inner layer contains Cr₂O₃. The scale formed in the atmosphere containing SO₂ is also comprised of two layers (outer MnCr₂O₄ and inner Cr₂O₃). The analyses were carried out with the use of the ³⁵S isotope. The analyses of the phase composition and morphology of the formed scale were conducted with the use of SEM/EDX and TEM.