XPS Characterization of Oxide Films Formed on Fe-Cr Alloys during the Early Stage of Oxidation at 1273K

Abstract

The Fe-(10-30)Cr alloys were oxidized for 60s at 1273K in 0.05 atm H₂O-air with an infrared radiation furnace. Formed oxide films were characterized mainly by XPS:XRD and ellipsometric measurements were also done. As-rolled alloys were α single-phase except for a 10Cr alloy and the average grain size was 52±8μm(±1σ). They were polished with wet emery paper down to #1000, mirror finished with diamond slurry, and kept in a silica gel desiccator for one day bofore use. The pretreated specimens were covered with (Fe_1-yCr_y)OOH film of about 2nm thick which contained very small amount of silicate, manganese and sulfer species: y increased proportionally with Cr content in alloy but less than that in alloys. The oxide scale formed on 10Cr alloy at 1273K for 60s was thick and showed spalling: structure and composition of the scale are similar to those formed on type 430 stainless steel by breakaway oxidation. Thin oxide film of (Cr_1-xFe_x)₂O₃ was formed on (16-30)Cr alloys, x being less than 0.03 for 16Cr alloy and decreased with Cr content in alloy. The thickness was estimated to be more than 100nm and increased with Cr content in alloy. Bound water was detected only in the outermost part.