Preparation of spherical tungsten powder with uniform distribution of lanthania by plasma spheroidization

The high ductile-brittle transition temperature of tungsten (W) makes it prone to crack during additive manufacturing. Incorporating lanthania (La2O3) to tungsten had been proven to be an efficient way to solve the cracking problem. However, the current incorporation methods are often accompanied by problems such as uneven dispersion of lanthania. In this study, W-La2O3 spherical powder with uniform distribution of lanthania was successfully prepared by spray granulation, heat treatment, and plasma spheroidization. The morphology, particle size distribution, flowability, apparent density, and element distribution of W-La2O3 powder at different stages were studied. The results show that the final obtained W-La2O3 powder has smooth surface and narrow particle size distribution, which also has excellent flowability (8.2 s/50 g) and apparent density (10.7 g/cm3). Moreover, it was observed that the plasma spheroidization resulted in the decrease of lanthania content in the powder, and the law of variation of lanthania content was obtained by the linear fitting method. The spheroidization mechanism of W-La2O3 composite powders was also proposed by studying the microstructure of incompletely spheroidized powders and the change of lanthania content.