Iron Aluminide Coating on Steel Surface by Mechanical Alloying at Elevated Temperature

Abstract

  A new type of iron aluminide coating on a steel substrate by mechanical alloying (MA) with Al-Fe powders was examined. Precoating was carried out by a high-energy planetary MA with Al-Fe powder at room temperature, followed by low-energy MA at an elevated temperature. In MA at 500 ℃, the precoating layer becomes soft and the interdiffusion between Al and Fe is enhanced, resulting in the formation of a homogenous iron aluminide coating layer on a steel substrate. By MA at 500 ℃ for 4 h, a Fe₂Al₅ coating layer is formed for Al-25 at%Fe powder, and a FeAl coating layer with a small amount of Fe₂Al₅ is formed for Al-50 at%Fe powder. The Fe-Al solid solution is achieved near the steel substrate/coating layer interface in a substrate, resulting in good bonding between the substrate and the coating layer. The Al-50 at%Fe coating layer has a hardness of 7.8 GPa and high fracture toughness.