Effect of Ce and La additions in low temperature aluminization process by CVD-FBR on 12%Cr ferritic/martensitic steel and behaviour in steam oxidation

Two different coatings based of iron aluminide on 12% Cr ferritic-martensitic steel have been developed by CVD-FBR technique, which is modified by the introduction of Ce and La as powder in the fluidized bed. These elements change the gaseous environment, which composition is predicted by a thermodynamic approximation. Partial pressures of all gaseous precursors are drastically modified; in consequence AlCl has the highest partial pressure in the system leading to an increment of the coating thickness. Coatings are composed by (Fe, Cr)₂Al₅ or (Fe, Cr)₂Al₅ and (Fe, Cr)Al₃ intermetallic phases. On the other hand, steam oxidation test at 650 °C was performed in order to observe improvements in the HCM12A oxidation resistant.