Improving the physicochemical properties of Fe-25Cr ferritic steel for SOFC interconnects via Y-implantation and Y2O3-deposition

Abstract

The present study investigated the role of the reactive-element effect (REE) in improving the corrosion resistance, chromium vaporization rate, and electrical conductivity of the Fe-25Cr ferritic steel modified either by means of yttrium implantation or chemical deposition of yttrium oxide from metaloorganic compound vapors. The corrosion kinetics of the Fe-25Cr steel, both pure and modified, were determined under isothermal conditions in air and an Ar-H2-H2O gas mixture at 1,073 K. A significant improvement in corrosion resistance was observed after surface modification. XRD and SEM-EDS investigations showed that the protective Cr2O 3 layer formed the main part of the scale. Measurements of Cr vaporization rate in the air-H2O gas mixture revealed that both surface modifications of the steel significantly suppressed the formation of volatile chromium compounds to a large degree. The yttrium-implanted steels oxidized both in air and the Ar-H2-H2O mixture were characterized by the lowest area specific resistance and thereby did not exceed the acceptable ASR level (0.1 Ω cm2) for interconnect materials in the temperature range of 973-1,073 K, unlike pure steel and the steel coated with Y2O3. © 2012 The Author(s).