On the feasibility of using Sm2Fe17Nx powders obtained via HDDR process for laser powder bed fusion of bonded permanent magnets

Powders to be used as the main feedstock component for additive manufacturing processes, such as Laser Powder Bed Fusion (LPBF) technique, must present suitable technological properties, mainly high values of apparent density (AD) and flow rate (FR). These features are directly related to particle size, morphology, and size dis-tribution. Although these issues have already been addressed to feedstocks based on Nd-Fe-B powders, the po-tential use of Sm-Fe-N powder as a raw material for feedstock processes has been scarcely explored thus far. If on one hand it is well established in the literature that Sm-Fe-N particles should be small (approximate to 2 mu m) to present sufficiently high values of intrinsic coercivity (Hcj, > 700 kA/m), on the other hand, however, smaller particles exhibit AD and FR values that are not appropriate for use in LPBF. An alternative to circumvent this apparently conflicting situation is to refine the microstructure of the particles in order to increase coercivity, instead of reducing particle size itself, which could be achieved via Hydrogenation-Disproportionation-Desorption-Recombination (HDDR). Considering this context, the main objective of this work is to study the feasibility of using Sm2Fe17Nx-based powders produced via the HDDR process followed by nitrogenation to obtain as-printed bonded magnets by the LPBF process. AD and FR of sieved powders with two distinct granulometry (< 45 mu m and 45 < x < 63 mu m) were evaluated. The obtained HDDR Sm-Fe-N powders presented values of Hcj = 683-777 kA/ m, comparable to commercial nanocrystalline powders obtained by melt spinning. Powders were mixed with polyamide-12 (PA12) powder and used as feedstock to obtain bonded magnets by the LBPF technique. Micro -structural properties of the as-printed bonded magnets were analyzed by Scanning Electron Microscopy (SEM). The effect of the LPBF process on the structural and magnetic properties of HDDR Sm-Fe-N powders was eval-uated by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). Both coarser and finer powders presented no structural modifications or reduction in magnetic property values after the laser processing. However, denser as-printed bonded magnets were obtained using the coarser one, emerging as a potential candidate to be used as feedstock in LPBF process.