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.