Unexpected Coercivity Enhancement >1T for Nd-Fe-B Permanent Magnets With 20 wt% Nd Produced by Laser Powder Bed Fusion
Florian Bittner, Juliane Thielsch, Welf‐Guntram Drossel
Abstract
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 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu _{0}H_{c} =1.15$ </tex-math></inline-formula> 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> and laser focus diameter of 110 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> , which led to a threefold re-melting of the sample.