A comparative study of Ti-6Al-4V powders for additive manufacturing by gas atomization, plasma rotating electrode process and plasma atomization

In this study, it is the first time to overall compare three types of spherical Ti-6Al-4V powders by gas atomization, plasma rotating electrode process and plasma atomization in terms of microstructure, porosity, argon gas content and pore spatial structure using scanning electron microscopy, mass spectrometer gas analyzer and synchrotron X-ray computed tomography (CT). It is found that the particle size plays a crucial role in the micro-morphology, porosity and argon gas content of the atomized powders. The experimental results show that the argon content of the gas atomized (GAed), plasma rotating electrode processed (PREPed) and plasma atomized (PAed) powders below 150 μm is 0.77 ± 0.06, 0.16 ± 0.06 and 0.70 ± 0.06 μg/g, while its porosity is 0.20 ± 0.01%, 0.08 ± 0.01% and 0.12 ± 0.01%, respectively. Both argon content and porosity within powders increase with increasing particle size for each type of powders. The results of three-dimensional reconstructed images from CT scanning present that the pore population, size and porosity within powders gradually increase with the increase of particle size. The pore sphericity of the GAed and PAed powders exhibits relatively higher than that of the PREPed powders due to different gas pressures inside of powders.