Towards 3D printing of electrical machines

Laser powder bed fusion (LPBF) additive manufacturing (AM) allows the manufacturing of alloy compositions that are not viable or possible to manufacture by traditional methods. This work uses an alloy optimized to use in ferromagnetic parts of electrical machines. This alloy is composed of iron (Fe) and silicon (Si) with 6.7% of Si in weight (Fe-6.7Si). Cylindrical, cubic and ring-shaped samples are manufactured in order to obtain several mechanical (density/porosity, hardness and microstructure) and magnetic (anhysteretic and iron loss curves) properties. It has been determined that the manufacturing parameters (P “ 78W, v “ 400mm/s, h “ 60μm) present the best compromise in terms of mechanical properties (relative density of 95.49%, Vickers hardness of 303.4HV ̆8.52% and a very low crack density). The magnetic properties obtained in the as-built and annealed states (1150°C for 1h) at a frequency of 50Hz are respectively a magnetic saturation of 1.05T (equal for both states), a maximum relative magnetic permeability of 650 and 1205 and iron losses (for a magnetic induction of 1T) of 21.07W/kg and 23.30W/kg. Furthermore, it is shown that a heat treatment at 1150°C for 1h homogenizes the material which shows Si-rich segregations close to the melt boundaries in the as-built state. The e↵ects of residual stresses that are high in LPBF fabricated samples are also discussed in this work.