Effect of Dispersion of Rare Earth Oxides on the High Temperature Oxidation Resistance of Sintered Fe-20Cr Alloy

Abstract

The isothermal oxidation behavior in air at 1000, 1050 and 1100°C of Fe-20Cr alloys with 1 wt% dispersion of Y₂O₃, La₂O₃, Al₂O₃, TiO₂, SiO₂ and Cr₂O₃ prepared by a conventional sintering and rolling procedure was examined. It was found that the dispersion of SiO₂, TiO₂ and Cr₂O₃ reduced the oxidation resistance, while the dispersion of La₂O₃ and Y₂O₃ excellently improved the oxidation resistance of Fe-20Cr alloy. The oxidation rates during the early stage of oxidation were apparently dependent on the type of the dispersed oxides, while the grain size of the alloys was not dependent on the type of the dispersed oxides. There was no evidence that the dispersed particles accumulated at the alloy-scale interface. Ion microanalyses of the Cr₂O₃ scales formed after 1 hr oxidation at 1100°C revealed that all the dispersed elements were incorporated in the scale and the iron content of the scale was lower on the alloys which exhibited better oxidation resistance.