Effect of CH4 on plasma spheroidization of tantalum powder

In this work, hydrogenation-dehydrogenation tantalum powder was spheroidized by plasma spheroidization to prepare high purity spherical tantalum powder suitable for use in additive manufacturing. The effects of methane (CH4) in sheath gas on morphology, property and chemical composition of spheroidized tantalum powder were investigated. The spheroidized tantalum powder showed increased spheroidization ratios up to 99.9% by comparison to that of raw powder. Compared to spheroidized tantalum powder obtained in argon (Ar) or Ar + hydrogen atmosphere, a significant reduction in oxygen content from 600 ppm to less than 200 ppm was observed with the addition of CH4. Excessive CH4 addition of 1.5 L/min also caused a sharp increase in carbon content from 250 ppm to 3300 ppm. These findings indicate that the addition of CH4 in spheroidization is an effective way to reduce oxygen content of tantalum powder and expected to be applied to the spheroidization of other powders.