直流等离子体球化钨粉制备及其性能研究

Preparation and Performance Study of Tungsten Powder by Direct-Current Plasma Spheroidization

直流电弧等离子体具有核心温度高、环境清洁等特点,且制备出的粉体球形度高、球化率高,成为增材制造用高质量粉体规模化生产的重要技术。以不规则钨粉为原料,采用直流电弧等离子体球化技术制备球形钨粉,研究不同送粉速率及送粉气流量对球化后粉末颗粒性能的影响,证明不规则钨粉球化过程中的3种转变机制,并在较大送粉气流量下,采用直流电弧等离子体球化技术原位合成了纳米颗粒附着的球形钨粉。采用扫描电子显微镜、X射线衍射仪、激光粒度仪、粉末流动性测试仪对球化后钨粉颗粒的形貌、物相、粒径分布、流动性及松装密度等进行分析表征。结果表明:经直流电弧等离子体球化后钨粉颗粒物相未发生变化,呈现出单一钨相,送粉速率为8 r·min^(-1)时,制备的钨粉颗粒表面光滑且球化率可达到98%以上,粒径分布相较于原料粉末变窄。球化后钨粉的流动性最高,达到5.35 s·50 g^(-1),相较原料钨粉减少了13.18 s;松装密度由5.37提高到11.67 g·cm^(-3),提高了117.3%。

Direct-current arc plasma has the characteristics of high core temperature and clean environment,and the prepared powders have high sphericity and spheroidization rate,making it an important technology for the large-scale production of high-quality powders for additive manufacturing.In this paper,spherical tungsten powder was prepared by direct-current arc plasma spheroidization technology using irregular tungsten powder as raw material.The effects of different feeding rates and powder delivery gas flow rate on the properties of spheroidized powder particles were studied.Three transformation mechanisms in the process of spheroidizing irregular tungsten powder were proved.Under a large powder delivery gas flow rate,spherical tungsten powder with nanoparticles was synthesized in-situ by direct-current plasma spheroidization technology.The morphology,phase,particle size distribution,flowability and apparent density of spheroidized tungsten powder particles were analyzed and characterized by scanning electron microscope,X-ray diffraction,laser particle size analyzer and powder flowability tester.The results show that the phase of tungsten powder particles does not change after direct-current plasma spheroidization,presenting a single tungsten phase.The tungsten powder particles prepared at a feeding rate of 8 r·min^(-1)have a smooth surface and a spheroidization rate of more than 98%,and the particle size distribution is narrower than that of raw tungsten powder.The flowability of spheroidized tungsten powder reaches 5.35 s·50 g^(-1),which is 13.18 s less than that of raw tungsten powder.The apparent density is increased from 5.37 to 11.67 g·cm^(-3),which is increased by 117.3%.