Effect of cobalt on the oxidation resistance of Pr(Nd)–Dy–Fe–Co–B materials

Resumo

The effect of cobalt on the oxidation resistance of (Nd_0.85Dy_0.15)_16.4(Fe_0.89Co_0.11)_74.4Ti_1.3B_7.9 and (Pr_0.56Dy_0.39Sm_0.05)_14.5(Fe_0.75Co_0.25)_78.8B_6.7 alloys has been studied. The storage of magnet blanks made from these alloy in air for 200 h does not affect the magnetic properties of the sintered magnets owing to the presence of the phases (Pr, Dy)(Fe, Co)₂, (Pr, Dy)(Fe, Co)₂B₂, (Pr, Dy)(Fe, Co)₄B, (Pr, Dy)(Fe, Co)₃B₂, and (Pr, Dy)(Fe, Co)₃, which are resistant to oxidation and ensure liquid-phase sintering of magnets. After 200-h exposure to air, oxidation of the blanks takes place, the rate of which decreases by more than two times at the expense of an increase in the cobalt content in the alloy.