Microstructure of spherical W-Ni-Fe prealloy powder prepared by spray granulation and debinding sintering combined with radiofrequency plasma spheroidization

Abstract

This study addresses the limitations of conventional W-Ni-Fe prealloyed powder preparation processes, such as low sphericity, high oxygen content, and elemental segregation, by developing an integrated spray granulation-debinding-sintering-(RF) plasma spheroidization process. This methodology meets the stringent requirements of additive manufacturing for high-performance powders. Through systematic optimization of spray granulation parameters (atomizer speed:10,000 rpm; inlet air temperature 150 °C; outlet air temperature 60 °C), near-spherical agglomerates with a flowability of 18.5 s/50 g were obtained. Subsequent debinding-sintering (debinding at 500 °C under negative pressure for 1.5 h, sintering at 1000 °C) effectively removed organic residues and enhanced densification. Final radio-frequency plasma spheroidization (feeding rate:7.8 g/min, carrier gas flow:3.0 L/min, Chamber press-ure:13.5 psi) achieved >95 % sphericity, oxygen content ≤200 ppm, flowability of 6.13 s/50 g and an apparent density of 10 g/cm³, with volatilization losses of 53.9 % for Ni and 55.9 % for Fe. The optimized powders exhibit homogeneous elemental distribution,66.9 % improved flowability compared to agglomerated powders, and a 75 % increase in apparent density with a narrowed particle size distribution, effectively mitigating the drawbacks of conventional powders. The composite process demonstrates sequential control of powder morphology and elemental homogeneity, producing high-performance W-Ni-Fe prealloyed powders suitable for extreme environments (nuclear reactors). This breakthrough provides a robust material solution for advanced additive manufacturing applications.