Laser powder fusing as an additive manufacturing process to createtheferromagnetic coatingson the basis of Fe and Sm powderson stainless steel substrate

摘要

A robotic laser technological complex has been used for the laser powder fusing (LPF) of samarium (Sm) and iron (Fe)powders on stainless steel (SS) substrate in argon flow conditions for the creation of thick (1.0–1.5 mm) ferromagneticcoatings. The formation of Fe–Sm–Ni–Cr and Fe–Cr–Sm alloys was demonstrated on SS substrate due to intensivediffusion of Fe, Cr and Ni atoms from the substrate. A magnetic field (0.2 T) during LPF on the SS substrate resulted incrystallisation of single grains (5–20 microns) of the Fe–Cr–Sm alloy with mutually perpendicular orientation, whichwere embedded in the Sm–Fe–Ni–Cr alloy matrix and formed a mesh structure in the fused layer. When the additionalmagnetic field was absent during LPF the larger part of Sm atoms were located in near-surface sample area and aroundelongated grains, as well as in small grains of spherical form, but dissolution of Sm was blocked in elongated grains. Thefused layers from Sm and Fe powders on SS substrates with and without magnetic field had a low coercivity (20–100Oe), near zero residual magnetisation and high saturation magnetisation (110–112 emu/g) at 300 K. The maximumcoercivity (100 Oe) was observed for coating fused with magnetic field, corresponding to mutually perpendicularorientation of ferromagnetic Fe–Cr–Sm grains. The cooling of samples to 4 K resulted in magnetic ordering with a Curietemperature of 50 K and with small changes in coercivity.