Abstract
In this work, two Ti-6Al-4V powder lots were produced using two different techniques: plasma atomization and gas atomization, with the first producing more spherical particles than the second. Testing specimens were then manufactured with these powder lots using an identical set of printing parameters and the same laser powder bed fusion system. Next, the porosity levels and distributions as well as the static and fatigue properties of the specimens from both powder lots were compared. Regarding the static mechanical properties, a noticeable difference was observed between the plasma-atomized powder specimens and their gas-atomized equivalents (7% greater ultimate and 4% greater yield strengths, but 3% lower elongation to failure, respectively). However, with regard to the fatigue resistance, the advantages of the plasma-atomized powder specimens in terms of their mechanical resistance were somewhat counterbalanced by the presence of pores aligned in the direction perpendicular to that of applied load. Conversely, specimens printed with the gas-atomized powder manifested a similar level of porosity, but a uniform pore distribution, which reduced the impact of the processing-induced porosity on fatigue cracks initiation and propagation.
Highlights
In this work, two Ti-6Al-4V powder lots were produced using two different techniques: plasma atomization and gas atomization, with the first producing more spherical particles than the second
These powders are produced using gas, plasma, and water atomization processes, each yielding powders with specific particle characteristics in terms of their morphology, size, internal porosity, and surface texture [3,4]. These characteristics highly influence the flow properties and the packing efficiency of the powders, and multiple studies have investigated these relationships [5,6,7,8]. Common conclusions of these studies include the observation that spherical particles improve the powder flowability and packing efficiency, and that fine particles negatively impact the rheological behavior as they involve a larger contact surface and a propensity to agglomeration
Regarding the particle size distribution of the selected powder lots (Figure 2c and Table 2), it can be seen that the two powders have significantly similar particle size distributions (PSDs), with the plasma-atomized powder having a slightly wider distribution shifted toward finer particles
Summary
Two Ti-6Al-4V powder lots were produced using two different techniques: plasma atomization and gas atomization, with the first producing more spherical particles than the second. A large panel of metals and alloys in powdered form can be used to manufacture parts with the LPBF process These powders are produced using gas, plasma, and water atomization processes, each yielding powders with specific particle characteristics in terms of their morphology, size, internal porosity, and surface texture [3,4]. Seyda and Herzog [3] tested three Ti-6Al-4V powder lots produced using different production routes, namely, gas atomization, plasma atomization and induction plasma spheroidization They noticed that the observed differences in terms of particle morphology and surface texture did not significantly impact the parts densities and mechanical properties. All these results indicate that an appropriate LPBF powder feedstock cannot be devised without significant optimization efforts involving the optimization of the powder characteristics, and of the related LPBF process parameters
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