The current work presents the results of an investigation focused on the influence of process parameters on the melt-track stability and its consequence to the sample density printed out of NdFeB powder. Commercially available powder of Nd7.5Pr0.7Fe75.4Co2.5B8.8Zr2.6Ti2.5 alloy was investigated at the angle of application in selective laser melting of permanent magnets. Using single track printing the stability of the melt pool was investigated under changing process parameters. The influence of changing laser power, scanning speed, and powder layer thickness on density, porosity structure, microstructure, phase composition, and magnetic properties were investigated. The results showed that energy density coupled with powder layer thickness plays a crucial role in melt-track stability. It was possible to manufacture magnets of both high relative density and high magnetic properties. Magnetization tests showed a significant correlation between the shape of the demagnetization curve and the layer height. While small layer heights are beneficial for sufficient magnetic properties, the remaining main parameters tend to affect the magnetic properties less. A quasi-linear correlation between the layer height and the magnetic properties remanence (J r ), coercivity (H cJ ) and maximum energy product ((BH) max ) was found.Materials 2020, 13, 139 2 of 14 specific tooling requirements for each design and limitations in shape flexibility and complexity [15,16]. With the technique of additive manufacturing it is possible to produce parts with more complex design; however, obtaining printing processes for functional materials is still a topic in research and development. Earlier research already showed that techniques such as slurry jetting or laser powder bed fusion (LPBF) proved to be capable of delivering net-shape magnets [17][18][19][20][21][22]. Slurry jetting has been shown to be capable of producing magnets with good magnetic properties (H cJ = 775.3 kA/m, J r = 0.478 T, and (BH) max = 39.78 kJ/m 3 ). These values reach nearly half of the values expected for the bulk material. This manufacturing approach allows the manufacture of the desired magnet in a timeand cost-efficient manner, however, and the resulting magnetic properties will always be lower than the bulk magnets, due to the presence of a significant quantity of bonding resin. Another approach was presented by Kolb et al. [17,18] who utilized laser powder based fusion (LPBF) technique in order to overcome the problem of low relative density. They managed to 3D print cubical magnets of 85% of relative density, which were characterized by a polarization of 0.514 T. The surprisingly lower than expected magnetic properties were assigned to the self-demagnetizing of the samples while measured in an open magnetic circuit inside a Helmholtz coil. Other researchers [19] also applied a laser powder based fusion (LPBF) process to the powdered NdFeB (Nd7.5Pr0.7Zr2.6Ti2.5-Co2.5Fe75B8.8) powder. The 3D printed magnet reached roughly 60% of a bulk counterpart at relative d...

Nowadays many materials such as steels, aluminium and titanium alloys can be realised by powder bed solutions melting subsequently powder layers by means of a laser or electron beam (Laser Beam Melting -LBM and Electron Beam Melting -EBM). The microstructure realised by layer-by-layer solidification having high cooling rate cannot be considered isotropic. Therefore, the mechanical properties could be influenced by the building direction. Regarding maraging steel, the study of the influence of the building direction and the heat treatment on the static and axial fatigue strength has been investigated in a previous contribution. A large scatter of the fatigue test results was found because of the presence of detrimental surface and subsurface defects. The aim of this contribution is to present additional axial fatigue test results of maraging steel characterized by different build orientation and providing an analysis of the defects observed at the crack initiation area of the fracture surface. Materials and methods Material and specimen's geometryMATEC Web of Conferences 165, 02005 (2018)

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