High Temperature Oxidation of a Work Roll Grade High-Chromium White Cast Iron

High-chromium white cast iron is a common material for the manufacture of the work rolls used in the finishing stands in hot strip mills. The high temperature oxidation behaviour of as-cast and heat-treated high-chromium white cast iron was studied by gravimetric means at 650 °C in atmospheres that included dry air and a mixture of dry air and water vapour. For both environmental and material conditions, the oxidation rate of the alloys was represented by parabolic trends and the oxidation phenomenon was more obvious when the samples were oxidised in water vapour. Water vapour also influenced the chemical composition of the oxides formed in the alloy and under this condition, the oxide scale formed on the alloy contained the oxides FeCr2O4, (Fe, Cr)3O4 and (Fe, Cr)2O3. In contrast, the alloys exposed to dry air conditions only experienced the formation of FeCr2O4 and (Fe, Cr)2O3. It was found that the presence of water vapour and the chromium content of the alloys increased the oxidation rate by a mechanism that involved chromium depletion of the oxide as a result of hydroxide formation. The differences observed in the oxidation behaviour of the alloy are discussed in terms of the composition of the oxidant atmosphere and the metallurgical condition of the specimens.