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

Abstract

The impact of laser powder bed fusion (LPBF) on coercivity of Nd-lean commercial MQPTM-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 (μ0Hc = 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 μm and laser focus diameter of 110 μm, which led to a threefold re-melting of the sample.