Unexpected Coercivity Enhancement >1T for Nd-Fe-B Permanent Magnets With 20 wt% Nd Produced by Laser Powder Bed Fusion

The impact of laser powder bed fusion (LPBF) on coercivity of Nd-lean commercial MQP™-S powder is investigated. It is found that different processing parameters, such as laser power, scan velocity, and hatch spacing, have a remarkable impact on the magnetic performance of LPBF-processed Nd–Fe–B permanent magnets. The increase of energy input during manufacturing will also increase coercivity and a maximum value of 920 kA/m ( $\mu _{0}H_{c} =1.15$ T) was achieved without any further post-processing. Among other parameters, hatch spacing was identified as the major contribution to coercivity and its role is discussed on basis of the several re-melting events if hatch spacing becomes increasingly smaller than the laser focus diameter. The maximum coercivity is obtained, for hatch spacing of 35 $\mu \text{m}$ and laser focus diameter of 110 $\mu \text{m}$ , which led to a threefold re-melting of the sample.