In recent years, with the rapid development of 3D printing technology, NiTi alloy powder has attracted much attention as a key raw material for biomedical implants. As the foundation of 3D printing, the quality of powder raw materials is crucial, and the plasma rotating electrode atomization method has attracted much attention.
Preparation method of plasma rotating electrode
The PREP method is used to prepare NiTi alloy powder, and the equipment mainly includes a rotary feed mechanism, an atomization chamber, a plasma gun device, and a feeding mechanism. Using NiTi alloy rods as raw materials, they are made into electrode rods and melted at high temperatures generated by plasma gun arcs. By utilizing the centrifugal force generated by the high-speed rotation of the electrode rod itself, melted metal is instantly ejected and rapidly solidified into spherical powder in a cooling medium. During the preparation process, high-purity argon gas is used as a protective gas with a purity of 4N (99.99%). By adjusting parameters such as plasma gun main current, spindle speed, and bar feed rate, the preparation conditions were optimized.
Powder characteristics
The powder particle size is mainly distributed between 60 and 125 μ m. Through scanning electron microscopy observation, it was found that the condensed tissue of larger particles (≥ 178 μ m) is a cellular crystal structure with poor surface smoothness; Small particles (≤ 40 μ m) have a smooth surface and no obvious crystalline structure.
Microstructure
The microstructure of powders with different particle sizes was observed by scanning electron microscopy and transmission electron microscopy. It was found that as the particle size decreased, the microstructure of the powder gradually refined, and the cellular crystal structure gradually disappeared, transforming into a finer equiaxed crystal structure. At the same time, more dislocations and twinning structures appeared in powders with smaller particle sizes, which had a significant impact on the phase transition behavior and mechanical properties of the powder.
The spherical NiTi alloy powder prepared by PREP method has the advantages of high sphericity, less hollow powder and satellite powder, and is very suitable as a raw material powder for 3D printing technology. The results of this study have important guiding significance for improving the performance of 3D printed products and optimizing 3D printing processes
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