Production of titanium fine powders based on the shuttle of the disproportionation and proportionation reactions of titanium ions in molten salt

Producing low cost and high-quality titanium powder is crucial for powder metallurgy (PM) and additive manufacturing (AM) of titanium-based material, which is one of the typical materials that is difficult to be manufactured by the traditional methods. Conventionally, titanium powder is produced by methods such as gas atomization (GA), plasma atomization (PA), hydride de-hydride (HDH), rotation electrode process (REP) and plasma rotation electrode process (PREP), which have disadvantages such as extremely high temperature operation or low yielding efficiency. In this study, a novel titanium-powder-production process was developed through the shuttle of disproportionation reaction (Ti^2＋ →Ti^3＋＋Ti^powder) and its backward reaction (Ti^3＋＋Ti^bulk →Ti^2＋) of Ti ions in molten salt. The proper selection of molten salt with suitable equilibrium constant of titanium ions and the promotion of the ion transfer in the salt were found critical for the production efficiency of titanium powder. As typical examples, production of titanium powder in molten LiCl-KCl and NaCl-KCl was carried out at the temperature range of 773 ～1023 K. It was found that more than 10 times by mass of titanium powder comparing to the added titanium ion was obtained with the addition of only 0.2 mol% of TiCl₂ into the salt. The particle size of the primary powder formed was found smaller than 1 μm, while the secondary agglomerated particle size was in the range of several tens μm. The proposed method is expected to significantly decrease the production cost of titanium-based powders.