PSI - Issue 53

Mariana Cunha et al. / Procedia Structural Integrity 53 (2024) 386–396 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Figure 2- Particle size range-wise yield of milled powders (wt. %) for each milling procedure

Powder particles from PND 1 exhibited a distinct flake-like shape and irregularity, as seen in Figure 3, with an aspect ratio (AR) of 0.5 unlike spherical powders (with AR close to 1) commonly used for AM printings, which are typically produced through gas atomization process. Moreover, the cold-welding phenomenon characterized by the bonding of smaller particles during the milling process can be observed in magnified section of Figure 3. As mentioned earlier, the typical size range for metal powders utilized in L-DED falls between 50 and 150 µm. However, for this study it was decided to use metal powders with a size range between 38 and 212 µm after carefully considering the density and flowability measurements of either particle size ranges (Table 4). This evaluation reveals that the use of a larger size rang can provide a better flowability and densification. This behaviour is attributed to the accommodation of particles of a larger size range.

Figure 3- SEM image of particles with a size between 38 µm and 212 µm resultant from PND 1

Table 4 Loose & tap density, and flowability of powders of different particle sizes

PPS (µm)

Loose density (g/cm 3 )

Tap density (g/cm3)

Flowability

53-150 38-212

2.96 3.35

3.95 4.14

19.40 15.02