PSI - Issue 77

V. Kroužecký et al. / Procedia Structural Integrity 77 (2026) 161 – 169 Vít Kroužecký / Structural Integrity Procedia 00 (2026) 000 – 000

163

3

(Aziz et al., 2025; Hajnys et al., 2019; Li et al., 2022, 2022; Trubačová et al., 2016) . As-built microstructures are predominantly γ -austenite with cellular – columnar grains, whose morphology and orientation influence mechanical response and fatigue behavior (Hajnys et al., 2019; Iron and Steel Institute of Z. I. Nekrasov National Academy of Sciences of Ukraine et al., 2022; Trubačová et al., 2016) . Porosity and lack-of-fusion defects adversely affect strength and overall performance and are sensitive to powder quality, particle size distribution (PSD), and build orientation (Deng et al., 2020; Król et al., 2018). Process refinements such as two-step remelting or post-processing techniques (such as electropolishing and laser polishing) have been shown to increase density and reduce surface roughness, thereby enhancing wear resistance (Fang et al., 2025; Lu et al., 2020; Lyczkowska-Widlak et al., 2019). Surface roughness critically affects fatigue life and functional performance. Its prediction through process parameters enables targeted post-processing strategies to meet application-specific requirements. (Fang et al., 2025; Wang et al., 2024). 2. Material and experimental procedures The experimental specimens were fabricated by selective laser melting (SLM) using an EOS M290 system (EOS GmbH, Germany). The machine is equipped with a single 400 W fiber laser featuring a focal spot size of 100 μm Throughout the process, the build chamber was filled with an inert argon atmosphere to minimize oxidation. A hard recoater made of high-speed steel (HSS) was for setting powder. The build platform was preheated to 80 °C, and the nominal layer thickness was set to 40 μm. The specimens were produced using repeatedly recycled 316L stainless steel powder. The chemical composition of the powder is presented in Table 1 Chemical composition

Table 1 Chemical composition

Cr

Ni

Mo

Mn

Si

Cu

N

C

P

O

Element

Fe

17

13

2,25 2,79 3,00

Min

Balance

17,79

14,05

1,3

0,51

0,17 ≤0,5

0,07 ≤0,1

0,012 ≤0,03

0,016

0,046

Result

19

15

≤2,0

≤0,75

≤0,025

Max

Analysis of powder The 316L stainless steel powder used in this study had undergone multiple recycling cycles and was characterized in terms of particle size distribution and morphology. Particle size distribution was determined using image analysis, and the characteristic values (D10, D50, and D90) are summarized in Table 2. Powder morphology was assessed by scanning electron microscopy (SEM), with particular attention paid to particle sphericity and the presence of satellite particles. Comparison with the manufacturer’s spe cified limits (Table 2 Particle size distribution) indicates that the recycled powder exhibits a shift toward finer particles, with D10 and D50 below the lower limit and D90 slightly below the specified range. Morphological analysis revealed that the sphericity of the recycled powder did not meet the minimum requirement, while the aspect ratio exceeded the upper limit. These findings demonstrate that the repeatedly recycled powder no longer conforms to the manufacturer’s specifications, which may negatively affect the stability and quality of the SLM process.

Table 2 Particle size distribution

Used powder Virgin powder

Limits

D10 [µm] D50 [µm] D90 [µm] Sphericity Aspect ratio

5,8

21 32 46

20-32 32-44 48-65

19,2 40,7

0,871 1,196

0,907 0,851

≥0,891 ≥0,832