Interfacial Characteristics of Iron Aluminides Intermetallic Layers on Al-Coated Steel Sheet

The characteristics of Al-coating materials on low carbon steel sheets during high temperature oxidation process were investigated. The phases’ evolution and growth were systematically evaluated by SEM/EDS and XRD. The hardness distribution from the surface to the steel substrate was measured to check the brittleness of iron aluminides coating layers. The oxidation properties of coating materials were investigated using weight gain method. Intermetallic compound recognized as FeAl3 was initially formed on the interface between steel substrate and coating materials. After exposing the specimens at elevated temperature, FeAl3 layer was gradually transformed into Fe2Al5, FeAl2, and FeAl+Fe3Al. Oxidation rate increased fastly after α-Al in the coating completely transformed at 650 °C. The brittle FeAl3 and Fe2Al5 have the lower resistance to oxidation because the easier cracking during intermetallic reaction.