Effect of Tempering on the Oxidation Resistance of a Work Roll Grade High-Chromium White Cast Iron

The high-temperature oxidation resistance of as-cast and heat-treated specimens of a high-chromium white cast iron for hot mill work rolls was investigated by gravimetric means under isothermal oxidation conditions in dry air at 650 A degrees C. Results from the experiments revealed that the chromium content of the matrix and the carbide area fraction of the samples significantly affect the extent of oxidation. Even so, the oxidation phenomenon could always be described by the parabolic rate law. The surface morphology and cross-section of the samples were studied by means of X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analyses, confirming that the oxidation behaviour of the alloys is sensitive to tempering heat treatment schedule. The impact of heat-treatment on the oxidation resistance of the work roll alloys is discussed in terms of their microstructural modification.