High-Temperature Oxidation Behavior of Fe-20Cr-4 Al Alloys with Small Additions of Cerium(Metallurgy)
The oxidation behavior of Fe-20Cr-4 Al alloys, some containing 0.01, 0.04 and 0.37%Ce, was studied in air at temperatures between 1273 and 1523K by weight-change measurements, X-ray diffraction, electron probe microanalysis and scanning electron microscopy. The surface oxide predominantly formed on all the alloys was α-Al_2O_3. The marker and kinetic studies suggested the α-Al_2O_3 scale grew into the alloys by inward diffusion of oxygen along the oxide grain boundaries. In the alloys without Ce and with 0.01% Ce, the α-Al_2O_3 Scale spalled during cooling from the oxidation temperature. Spalling of the surface oxide, probably caused by the formation of voids at the oxide-alloy interface, initially occurred at the intersection of the alloy grain boundaries, and subsequently extended to the interior of the grains. No spalling was observed on the surfaces of the alloys with 0.04 and 0.37% Ce. In both alloys, cerium primarily existed as a Ce-Fe inter-metallic compound throughout the alloy matrix, which mostly precipitated at the grain boundaries. Higher cerium additions resulted in good adherence of surface oxide due to the prevention of voids formation at the oxide-alloy interface, and pegging of intergranular oxides preferentially formed at the alloy grain boundaries.
- Science reports of the Research Institutes, Tohoku University. Ser. A, Physics, chemistry and metallurgy
Science reports of the Research Institutes, Tohoku University. Ser. A, Physics, chemistry and metallurgy 27 95-96, 1979