Research On Nitrogen Quenching Process Of Sm-Fe-N Powder Prepared By High-pressure Atomizing System

Samarium-nitrogen-based permanent magnet materials have more excellent property,such as higher curie temperature,better thermal stability,stronger oxidation resistance and longer corrosion resistance than samarium-cobalt and neodymium-iron-boron alloy materials,which created a phenomenon for study of Sm-Fe-N permanent magnet materials in recent ten years.However,more effort should be made because there were still no proper methods to prepare Sm-Fe-N based materials which contained characteristics of low energy consumption and high efficiency.Theoretical analysis was applied to study the relationship between nitrogen quenching pressure and cooling rate during the process of Sm Fe alloy nitrogen quenching.In order to investigate the effect of cooling rate on the laws for the phase structure development and micro-morphology in Sm Fe alloy,melt quenching and Sm Fe alloy nitriding experiment and X-Ray and SEM-EDX methods were performed,and thus providing fundamental theory with pressure atomization nitrogen quenching process prepare Sm-Fe-N powder.The theoretical analysis indicated that cooling rate was on the increased trend with the increase of quenching pressure for different particle size.The Sm Fe droplets cooling rate could reach to 7.7×105K/s when the quenching pressure and particle size less than 50?m,respectively.Melt quenching experiment results showed that thickness of melt spinning could from 15 to 55 ?m when the rapid quenching rates changed from 10 reach to 40 m/s.The cooling rate of Sm Fe alloy ribbon was 7.5×105K/s when the rapid quenching rates was 28 m/s,which was in good agreement with theoretical analysis.The XRD and SEM-EDX demonstrated that Sm Fe alloy ribbon mainly included Sm2Fe17 and Sm Fe7 phases,and the crystal structure was slightly larger for the micro-morphology when the cooling rate less than 7.5×105K/s,which could make s difference for magnetic properties.When the cooling rate less than 7.5×105K/s,the phase only contained Sm2Fe17,meanwhile the crystal structure was relatively small and regularly array.Nitriding experiment indicated that nitriding time was over 3h while the reaction temperature was between 450 to 510?.The maximum nitriding could reach to 2.279 wt.% under nitriding time was 5h.The main nitriding products was Sm2Fe17 Nx and Sm2Fe17.However,the unique advantages of the technology for the preparation of Sm-Fe-N powder through high-pressure gas atomization would be invaluable in the exploration of the technology of preparing Sm Fe based permanent magnet materials.Therefore,further research was needed...