PSI - Issue 17

Thomas Simson et al. / Procedia Structural Integrity 17 (2019) 843–849

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Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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and “waste” powder which accumulates in areas outside the process frame due to liquid splashes expelled from the melt bath. The corresponding particle size distributions are depicted in Fig. 3. The original fresh powder (Fig. 2a) exhibits the typical morphology of inertly gas atomized molten metal particles which are mainly spherical in shape, exhibit a slight satellite formation (adherent fine particles from collisions during atomization) and only a few irregular particle s. If compared to the “used” powders (Fig. 2b), the differences are only marginal. This is also displayed by the corresponding particle size distributions which are nearly identical for the “new” and repeatedly “used” powders (Fig. 3). Only a tendency can be observed in the form of a slight broadening of the size distribution width and a reduction of finest particles after multiple use.

a)

b)

c)

50 µm

50 µm

200 µm

25 µm

25 µm

50 µm

5 µm

5 µm

25 µm

Fig. 2. Representative SEM micrographs of the steel powders used within this study: (a) “ new ” , (b) “ used ” and (c) “ waste ” powder fractions at different magnifications (note less magnification for (c)). White arrows point on surface oxides (dark areas).

Fig. 3. Particle size distribution of the investigated powder (a) “ new ” , (b) “ used ” and (c) “ waste ” .