Temperature dependence of the oxide growth on aluminized 9–12%Cr ferritic-martensitic steels exposed to water vapour oxidation

High temperature steam oxidation resistance of aluminide coatings obtained on 9–12% Cr ferritic-martensitic steels, which have been developed by chemical vapour deposition in fluidized bed reactor (CVD-FBR) using a bed modified with Zr particles, is presented here. The resulting coatings composed of (Fe,Cr)2Al5 intermetallic phase provide a high temperature steam oxidation resistance, which depends on the oxidation temperature. At 650 °C, after 1000 h of exposure, the alumina formed on the surface acts as a protective barrier. However, when the oxidation temperature increases up to 800 °C, the alumina scale fails before 1000 h of exposure giving rise to the formation of the Cr2O3 and (Fe,Mn)3O4, due to the high atomic diffusion rate at this temperature.