Physical Properties of Iron-Oxide Scales on Si-Containing Steels at High Temperature

Abstract

The mechanical properties of oxide scales at high-temperature were studied in order to improve the surface quality of commercial Si-containing high strength steels. Specific oxides of Fe₂O₃, Fe₃O₄, FeO and Fe₂SiO₄ were synthesized by powder metallurgy. The Vickers hardness, thermal expansion coefficient and thermal conductivity were measured at high-temperatures. A series of measurements confirmed that the physical properties of the synthesized oxides were different each other. From the Vickers hardness measurements, it was verified that the hardness of each synthesized oxide was identical with the naturally-formed iron oxide, as observed in the cross-section of oxide scales on steels. The influence of the Fe₂SiO₄ formed on Si-containing steels on the scale adhesion at high temperature and the surface property is discussed on the basis of the physical properties of the oxides.