Failure Modes of the Oxide Scale Formed on a Work Roll Grade High Speed Steel.

The behaviour of an oxide scale grown on the surface of a high-speed steel subjected to thermal cycling was studied. The oxide layer formed on the steel by means of the exposure of samples of this material to a mixture of dry air and water vapour at either 615 or 550 °C. The samples were held for 1 h at either temperature and were cooled to room temperature by quenching with distilled water. This procedure was repeated for up to forty cycles. The oxide layer was subjected to the action of thermal stresses generated during either the cooling or heating stages. It was found that both, the composition of the oxide layer and the amount of oxide spalled from the surface depended on the number of cycles imposed to the samples. The mechanisms that promote oxide spallation and the preferential composition of the oxides that remain on the surface of the steel after spallation are analyzed and discussed. [ABSTRACT FROM AUTHOR]