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Nitridation of RF-DC plasma N2-H2 into AISI420 produces several phases namely α' (bcc), ε (hcp), and γ (fcc) which are randomly distributed in a number that is difficult to identify, so the most dominant justification phase. Increases hardness and percentage of the relative magnetic in the α’ phase microstructure can be attributed to isothermal transformation during plasma nitriding from the ferromagnetic martensitic α’ phase to paramagnetic martensitic ε phase, and to nonmagnetic martensitic γ phase. This study measured the magnetic properties of AISI420 (without nitridation and nitridation with the optimization parameters of RF-DC plasma N2-N2) using Vibrating Sample Magnetometer. The AISI420 without nitridation has a low nitrogen content whereas AISI420 which is crystallized with optimization parameters has a high nitrogen content because it has a higher coercivity value with lower saturation magnetic moments. Low nitrogen content forms alloys in the soft-magnetic phase, while in high nitrogen content the average value of saturation magnetic moments decreases and coercivity increases. The saturation magnetic moment value (Ms) of AISI420 was optimized by the optimization parameter was 1.91 emu/gr.Oe. It can be identified that the microstructure of AISI420 that was nitridation using optimization parameters had the dominant ε-Fe3N phase. The susceptibility value of AISI420 was optimized by the optimization parameter 8.48 × 10-5 emu/gr.Oe up to 2.52 × 10-3 emu/gr.Oe. The range of susceptibility values was 10-5 to 10-3 so that it meets the criteria of 10-5 < 10-3 which can be categorized as paramagnetic and super-paramagnetic material. The AISI420 was treated using optimization of process RF-DC plasma N2-H2 has the dominant ε-Fe3N phase with trigonal hexagonal close-packed (hcp) microstructure in space P312 (149) super-paramagnetic.

AISI420; Magnetic Property; N2-H2; Plasma; RF-DC.