Study on the Plasma Rotating Electrode Atomization Technique for Core-Shell Powder Synthesis

By modifying the existing plasma rotating electrode atomization (PREP) powder production equipment, the core-shell structure powders with low nitrogen content in the core and high nitrogen content on the surface were successfully prepared by adjusting the nitrogen flow rate during the powder-making process with pure titanium rods. The particle size distribution, microscopic morphology, and microstructure of the powders were systematically characterized using a standard vibrating sieve, laser particle size analyzer, X-ray diffractometer (XRD), scanning electron microscope (SEM), and X-ray photoelectron spectroscope (XPS). The results show that the particle size of the powders with nitrogen gas were smaller than that without nitrogen gas. As the nitrogen flow rate increases from 3 L/min to 8 L/min, the particle size exhibits a trend of first decreasing and then increasing. Introducing nitrogen gas can significantly suppress the formation of satellite powders in pure titanium metal powders and make the surface of the powders smooth, but it can also result in elongated and insufficiently spheroidized shaped powder particles in the powder. Under different nitrogen gas flow rates, nitrogen is uniformly distributed on the powder surface, forming a Ti-Nx microstructures shell layer, and the nitrogen content on the powder surface layer is significantly higher than that in the core.