The morphology of oxidation of alumina-forming iron-base alloys containing chromium and aluminum

Abstract

A series of iron-base alloys containing different amounts of Cr and Al have been oxidized at$P_{O_{_2 } } = 2 \times 10^{ - 1}$ atm and at$P_{O_{_2 } } = 10^{ - 18}$ atm. The morphologies of the A1₂O₃ scales depend on the heating rate of the specimens, the Cr content of the alloys, and the$P_{O_{_2 } }$ of the environment. When the specimens are slowly introduced in the hot zone and oxidized in air, all the alloys form Al₂O₃ scales with a convoluted morphology. The extent of the convolutions decreases with increase in the Cr content. When the specimens are rapidly heated and oxidized in air, the low Cr-containing alloys form internal oxides and a surface scale of Al₂O₃ which shows no convolutions. In the higher Cr containing alloys, the internal oxidation is limited. In the low$P_{O_{_2 } }$.