Investigation into the regulation of particle size and morphology of Nb521 alloy powders produced by ultra-high-speed plasma rotating electrode process

The plasma rotating electrode process (PREP) is a key technology for producing high-quality spherical powders used in additive manufacturing and hot isostatic pressing. However, its application in large-scale industrial production is limited by the low yield of fine powders. In this study, ultra-high-speed PREP was employed to prepare Nb521 alloy powder. The effects of electrode rotating speed and plasma current parameters on particle size distribution (PSD), morphology, and powder properties were systematically investigated to address the technical bottleneck of fine powder yield. The results show that the Nb521 alloy powder produced by PREP exhibits a smooth surface and high sphericity, with a spheroidisation rate of 96.9%. The powder demonstrates excellent performance, with a flowability of 11.0 s/50 g and an apparent density of 5.39 g/cm 3 . As the rotating speed increases from 18,000 to 27,000 rpm, the median particle size (D50) decreases from 82.35 to 53.70 μm. Consequently, the fraction of fine powder (below 53 μm) significantly increases from 6.6% to 48.0%, leading to a substantial improvement in fine powder yield. Plasma current parameters have a minimal impact on particle size and morphology. The established rotating speed-particle size model effectively predicts the size range of Nb521 alloy powder, providing theoretical guidance for the preparation and process optimisation of high-performance refractory alloy powders.