Peculiarities of the microstructure and properties of iron aluminide powders obtained by the method of plasma-arc spheroidization

Iron aluminide powders obtained by the method of plasma-arc spraying of a flux-cored conductive wire with a steel shell and an aluminium filler were investigated. The experi­ments were carried out in an argon environment on the “PLAZAR-50-PL-W” installation. It was established that at all operation modes of the plasma torch, the sputtered particles are mostly spherical in shape. The number of particles of non-spherical shape is 7–12% in powders of the –315+200 mm fraction and in smaller fractions it is equal to 4–5%. The main phases of the obtained materials are Fe3Al and FeAl iron aluminides in various ratios. In all powder fractions the amount of the metal component is greater than of the oxide component. The number of oxides increases with a decrease in the powder fraction and a decrease in the plasma torch current. Under spraying at a current of 220 and 270 A in the powder fraction –200 + 100 mm, a larger amount of aluminides 83.88 and 86.30 and the lowest content of oxides up to 10–18% was recorded. In smaller powder fractions the content of aluminides is 70.38–75.68, and the amount of the oxide component increases to 29.62 wt%. The microhardness of metal particles is 3.07–4.59 GPa. Oxide particles consist mainly of Fe3O4 and Fe2O3 iron oxides and have a higher microhardness of 5.32–8.15 GPa under all spraying modes. The obtained powders can be recommended in 3D production for the direct energy deposition method, which includes laser deposition processes (DMD – Direct Metal Deposition). These materials can be used in the pro­duction of precise workpieces with a minimum allowance for mechanical processing using compaction methods in granular metallurgy – hot isostatic pressing (HIP).