PSI - Issue 77

M. Turhan et al. / Procedia Structural Integrity 77 (2026) 543–549

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M.Turhan et al. / Structural Integrity Procedia 00 (2026) 000 – 000

Later in the second set-up lower hatching teeth was changed to mode-off but rest of the parameters were kept same as first set-up. In the third set-up, only perforation was kept as mode-on but in the fourth set-up every feature was mode-off and additionally supports were reinforced by multiple line support. As it is seen from experimental set-ups, supports have been gradually gotten denser to have stable print [17].

a

b

Figure 2 (a) Adjustments of process parameters on EOSPRINT software for fourth experimental set-up; (b) 3D printed horizontal samples of fourth set-up shown with defects due to residual stress and missing supports (shown with red arrows).

While adjusting the support structures, the process parameters have been gradually improved. The colour configuration is shown in Figure 2 in picture a (on the left). The blue colour (substrate section) indicates UpSkin and DownSkin mode-off and modified by minimum time vector as 7 milliseconds to prevent from overheating the area to be exposed by laser scan. The yellow section was adjusted as DownSkin mode-off, the green section (support structure), and magenta section by default parameters. Support structures were designed densely in fourth set-up experiment. As seen in Figure 2 in picture b (on the right), there are missing supports and separations of supports from substrate. This may be caused due to breaking the support by chipping with re-coater and residual stresses caused by thermal cycles [17-18]. The vertical samples were also prepared in same manner as horizontal ones which have dense support and optimized process parameters. Lastly, the heat exchanger unit was printed by default process parameters. Volume support which is solid support was used to connect the large surface of heat exchanger unit to the platform firmly and to avoid from any deformation during printing process. There was no overheating observed because the heat exchanger unit had direct connection to the solid substrate, no cross-sectional increment, and hollow structures which means lesser energy intensity in each layer [17]. 3. Results and discussions 3.1. Tensile tests The tensile test was carried out according to EN ISO 6892-1 standard. The test samples are labelled as Alloy HX (conventional HX), Vert HX (vertically printed EOS HX), and Hor HX (horizontally printed EOS HX). The test samples are grouped and numbered based on exposure atmosphere, exposure temperature, and exposure duration as seen in Table 4. Additionally, the test samples did not undergo any heat treatment prior to exposure and the tensile test which were meant they were proceeded in as-built conditions. Table 4 The tensile results of Alloy HX (conventional HX), Vert HX (vertically printed EOS HX), and Hor HX (horizontally printed EOS HX) at different exposures and atmosphere conditions.

Elongation at fracture A [%]

Material

Yield strength. [MPa]

Tensile strength. [MPa]

Reduction of area Z [%]

Modulus [GPa]

Exposure atm.

Exposure temp. [°C]

Exposure time [hrs.]

Alloy HX 1 Vert HX 1 Hor HX 1

422 543 507

801 772 621

47 32 45

67 58 54

182 141 107

None None None

None None None

None None None