Development and characterization of an iron aluminide coating on mild steel substrate obtained by friction surfacing and heat treatment

Iron aluminides are intermetallic Fe-Al alloys known for their high temperature corrosion and oxidation resistance, which makes them candidate materials for high temperature applications. In the present work, the formation of an iron aluminide layer on a mild steel substrate by friction stir surfacing of aluminium alloy AA6351 followed by isothermal heat treatment is reported. After Al-alloy deposition, the samples were subjected to annealing at temperature of 500, 550, 600 and 650 degrees C for various times up to 120 h. Microstructure analyses conducted by XRD and SEM/EDS indicated the formation of a homogenous layer of Fe2Al5 with average hardness value of 1070 HV for a 72-h treatment at 650 degrees C. The electrochemical corrosion behaviour of the developed coatings was analysed, and it was possible to show that friction stir surfacing followed by heat treatment constitutes an effective processing route for obtaining iron aluminide coatings on conventional steel substrates.