Preparation and microstructural evolution of spherical B-modified MoSi₂ powders by induction plasma spheroidization

In order to improve and consolidate the properties of boron (B)-modified molybdenum disilicide (MoSi₂) powders applied in selective laser melting and make them attractive candidate for selective laser melting, in this study, induction plasma spheroidization (IPS) was conducted to spheroidize Mo–62Si–5B (at.%) powders. Mo–62Si–5B powders prepared by mechanical crushing exhibited polygonal morphology and consisted of MoSi₂ and MoB₂ phases. Subsequently, spherical B-modified MoSi₂ powders with the size in the range of 45–100 μm were obtained via IPS. The effect of plasma power on the spheroidization rate, flowability, and oxygen content of the powders was investigated, which improved obviously with the increase of the plasma power. Powders spheroidized at the largest plasma power of 40 kW exhibited the highest spheroidization rate (89%) and the best flowability (25 s/50 g). Furthermore, morphological evolution and microstructural evolution of particles were systematically explored based on melting and solidification processes of powders. With the increase in heat absorption, the morphology of particles gets gradually converted from polygonal to spherical. The microstructure of spherical particles transforms from original hypoeutectic structure to cellular eutectic structure with the decrease in the powder size.