Formation of Iron-aluminide Coating through Annealing of Shrouded Plasma-sprayed Iron/Aluminum Composite

The formation of iron aluminide coating was attempted through annealing of plasma-sprayed iron/aluminum composite deposit.Shrouded plasma spraying with nitrogen as protective gas was employed to prepare iron/aluminum composite coating using mechanically blended iron and aluminum powders with Fe/Al atomic ratio of 65:35.Annealing of the as-sprayed coating was carried out in argon atmosphere at 450,500,550,and 600 o C for different durations.The microstructure of the coatings was characterized by scanning electron microscopy and X-ray diffraction.The effect of annealing on the microstructure and phase evolution in the coatings was examined.The results show that iron/aluminum composite coating with low oxide inclusions and porosity is deposited by shrouded plasma spraying.It is found that Fe2Al5 intermetallics forms as an intermediate phase in the composite coating during annealing.As the annealing duration and temperature increase,iron aluminide intermetallic phases in the coatings increase and the microstructure becomes more homogeneous.After annealing at 600 o C for 336 h,FeAl and Fe3Al intermetallic phases will present in the coating as the main phases.