Sm₂Co₁₇ permanent magnets prepared by PIM with PW-based binder

Powder injection molding (PIM) was used to prepare sintered Sm₂Co₁₇ magnets with paraffin wax (PW) based binder, which consists of 70% PW, 10% LEPE, 10% PP, and 10% SA (mass fraction). The binder is removed by thermal debinding in the mixing atmosphere of argon and hydrogen. The magnetic properties of the sintered PIM magnets are remanence B_r=0.51 T, intrinsic coercivity H_cj=168 kA·m^-1, and maximum energy product BH_max=21.3 kJ·m^-3. Compared with commercial magnets, the magnetic properties are poor because the PIM magnets have high carbon mass fraction (0.33%). Carbon consumes the effective content of Zr and forms high melting-point nonmagnetic phase (ZrC), which results in the decrease in volume content of lamella phase and 1:5 phase. Deterioration of the cellular structure and SEM structure leads to the decrease in magnetic properties of the PIM magnets. It is concluded that residual carbon in the magnets should be removed when the sintered magnets is prepared by PIM.