Fabrication of Ti6Al4V spherical powders for additive manufacturing from recycled shavings

Date

2025-8-14

Author

Uysal, Zeynep Ege

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Ti6Al4V is widely used across multiple industries. Additive manufacturing, particularly selective laser melting, allows near-net-shape production, but requires fine (15−53µm) spherical powders. This study investigates a recycling route to produce such powders from Ti6Al4V shavings. The first step was cleaning of shavings, studied in a number of routes. It was found that cleaning through washing machine was quite effective when used with fabric washing powders. Cleaned chips are then hydrogenated, milled, and plasma spheroidized into spherical powders. To determine conditions of hydriding, chips were hydrided isothermally for a fixed duration at temperatures from 450 to 650 °C. This showed that the amount of hydrogen absorbed increased with increasing temperature. Then, pressure-controlled experiments were carried out. This was challenging since hydrogen absorption leads to an uncontrolled rise in temperature. Hydriding, therefore, was carried out with flow-controlled delivery. This showed that chips can be hydrided to 3.3 wt.% at 400 °C for a duration of 5 hours. The hydrided chips were milled with a tumbling ball vi mill, which resulted in powders of irregular shape (<53µm) due to its brittleness. The plasma spheroidization was carried out at 25 kW, at feed rates of powders from 15 to 5 g/min. 10 g/min provided the best balance between spheroidization and process efficiency. It is concluded that direct spheroidization of hydrided powders in the plasma reactor is complicated, and dehydriding is necessary to successfully fabricate high-purity spherical powders from recycled chips. As a separate study, PCT diagram of Ti6Al4V was determined at 420, 480, and 520 °C.

Subject Keywords

Pressure controlled hydrogenation, Flow controlled hydrogenation, Mechanical milling, Activation for hydrogenation, Plasma spheroidization

URI

https://hdl.handle.net/11511/116222

Collections

Graduate School of Natural and Applied Sciences, Thesis