HIGH-COERCIVITY SM2FE17NX POWDERS PRODUCED BY HDDR AND NITRIDING PROCESSES

This paper describes the occurrence of HDDR (Hydrogenation Disproportionation Desorption Recombination or Hydrogen Decomposition Desorption Recombination) process in the processing of Sm2Fe17Nx powders with high coercivity. The hydrogen absorption and desorption behaviors of the Sm2Fe17 compound were studied. The Sm2Fe17 phase disproportionates into alpha-Fe and samarium hydrides after the heat treatment in hydrogen at around 600-1100-degrees-C. The removal of hydrogen by following a heat treatment in vacuum so that desorption and recombination occur, results in the reforming of the Sm2Fe17 Phase. This Sm2Fe17 phase has a cellular-like microstructure of about 50-500 nm in diameter. The nitrided Sm2Fe17 powders produced by the HDDR process at 775-degrees-C have high coercivity of 8.7 kOe.