PSI - Issue 83

E.N.T. Isidro et al. / Procedia Structural Integrity 83 (2026) 171–178

176

incomplete fusion and irregular pore distributions were prominent, with the stripes strategy showing greater interconnected porosity and a more severe impact on structural integrity. 3.2. Roughness The experimental roughness results allow for the evaluation of the influence of the process parameters on the surface quality. Table 5 presents the average Ra roughness values obtained for the different samples. Measurements were performed on the XY and XZ planes (see Figure 3). This is particularly relevant due to the anisotropy resulting from layer-by-layer manufacture characteristic (Figure 6).

Table 5. Average Ra roughness values.

Cube

VED

XY plane Mean X

XZ plane Mean Z

Mean Y

1 2 3 4 5 6 7 8 9

96.0 60.0 40.0 26.7 20.0 96.0 60.0 40.0 26.7 20.0

5.2 6.5

5.3 7.6

7.2 7.9 8.5 8.0 9.4 7.3 7.5 7.9 8.9

11.4 14.1 14.3 5.8 14.1 23.5 13.8 13.4

11.6 13.7 13.4

4.9 8.9

13.1 13.5 16.4

10

10.0

28

XY Plane - Measurement in X (Chessboard) XY Plane - Measurement in Y (Chessboard XZ Plane - Measurement in Z (Chessboard) XY Plane - Measurement in X (Stripes) XY Plane - Measurement in Y (Stripes) XZ Plane - Measurement in Z (Stripes)

23

18

13

Roughness [Ra]

8

3

98

90

82

74

66

58

50

42

34

26

18

VED [J/mm³]

Figure 6. Variation of roughness as a function of energy for different measurement orientations and scanning strategies. Seria conveniente modificar o gráfico: escala, disposição e cores para ficar diferente do gráfico do artigo completo

In the XY plane, a notable increase in roughness values along both the X and Y axes is observed at reduced energy levels, specifically at 26.7 and 20 J/mm³, where roughness surpasses 13 µm; this contrasts with values below 8 µm observed at elevated energies (60 and 96 J/mm³). This observation suggests possible problems with the powder fusion process, or an increase in surface imperfections caused by metal splatter. This is often seen in methods that use low energy densities. Moreover, the XZ plane, which is perpendicular to the substrate, usually shows more surface roughness. This is especially true when lower volumetric energy densities (VEDs) are used. However, the differences in roughness across different energy levels are less significant than those seen in the XY direction. This suggests that the "stair-step" effect, which is a key feature of the additive manufacturing process, has a greater impact on roughness. When comparing printed surfaces, those processed at higher energies (60-96 J/mm³) demonstrated lower roughness values (5.2 to 6.5 µm) on top surfaces, while side surfaces ranged from 7-8 µm, indicating that increased energy fosters better fusion and smoother upper surfaces. Conversely, at lower energy densities (20-26.7 J/mm³), the top surfaces showed greater roughness (up to 14.3 µm) compared to the side surfaces (7.5-10 µm). This was due to instability in the melt pool, which led to uneven fusion. Consequently, this resulted in splatter and unbonded particles accumulating on the horizontal plane.