Fe–Al composite layers on aluminum alloy formed by laser surface alloying with iron powder

Formation of Fe–Al composite thick layers by using laser surface alloying process with mixture of Al and Fe powders has been investigated to improve the surface hardness and the wear resistance of A5052 commercial Al–Mg alloy substrate. A continuous wave CO2 laser beam with the power of 2200 W was irradiated to the preplaced mixture powder on the substrate at various defocused distance of laser beam (30–150 mm up on the substrate) at the constant traveling speed (100 mm/min) in the argon gas shielding. The thickness of the laser alloyed layer varied from 0.5 to 7.0 mm. The microstructure of the laser alloyed layer changed with increasing Fe content from hypo-eutectic structure to hyper-eutectic structure with needle-like FeAl3, fine needle-like FeAl3 and finally lump-like Fe2Al5 compounds, and their hardnesses were HV100, HV100-300, HV300-500 and HV600-1000, respectively. The alloyed layers with the fine needle-like FeAl3 and Fe2Al5 compound structures showed the high hardness, HV300 and HV800, respectively, even at elevated temperatures up to 673 K. The wear resistance of the laser alloyed layer increased with increasing the hardness.