Nitriding Process and Magnetic Properties of Sm₂Fe₁₇N_x Powders Prepared by MG in Ar or NH₃

Abstract

Though the process composed of mechanical alloying, crystallization treatment and nitriding treatment has been used to prepare the Sm₂Fe₁₇N_X permanent magnet powders with high coercivity, the crystallization treatment increases the oxygen content in the specimen.
In this experiment, we tried to prepare the Sm₂Fe₁₇N_X powders by mechanical grinding(MG) and the nitriding treatment at as low temperature as 623K, where two kinds of powders;i.c., hydrogcnetcd Sm_2.5Fe₁₇ powder and non-treated Sm_2.5Fe₁₇ powder, were used as the starting materials, and MG was carried out in three kinds of atmosphere ; i.c., in Ar, N₂ and NH₃ gas.
Though the nitriding was promoted by the existence of hydrogen, the oxidation was also promoted. And it was confirmed that too much hydrogen in the specimen impede nitriding. This phenomenon suggests the existence of the most effective concentration of hydrogen for nitriding. In this work, the nitriding was carried out most effectively on the specimen mechanically ground in NH₃, where the nitrogen content after nitriding treatment was about 38000ppm.