Laser powder bed fusion applied to the manufacture of bulk or structured magnetic cores

Abstract

Rings based on pure iron have been manufactured by laser powder bed fusion. Different experimental conditions have been implemented to manufacture simple rings called “bulk”. Selected conditions were used to fabricate “structured” rings, made up of stacking of lamellae separated by weakly densified metal zones or by spacers. The magnetic properties of these rings were measured in order to determine their maximum flux density, their permeability and their magnetic losses. These properties, as well as the organizations of the magnetic domains observed by Magnetic Force Microscopy, were compared with those obtained for rings machined from castings parts or spark plasma sintered parts.The “bulk” rings resulting from laser fusion exhibit relatively high magnetic losses of the order of 80 W.kg−1 at 50 Hz under 1 T. However, this value can be lowered to about 30 W.kg−1 after a SPS treatment at 750 °C. In addition to lowering the magnetic losses, SPS annealing increases the densification of the material and thus the magnetic flux. The spacing of dense metal rings by less sintered zones or by spacers (“structured rings”), makes it possible to also greatly reduce the magnetic losses. Dividing these losses by a factor of 2 is thus possible by implementing a simple geometric arrangement.

Keywords

• Additive manufacturing
• Laser powder bed fusion
• Electric machines
• Soft magnetic materials
• Iron losses
• Magnetic domains