PSI - Issue 66

Vladimír Chmelko et al. / Procedia Structural Integrity 66 (2024) 426–432 Author name / Structural Integrity Procedia 00 (2025) 000–000

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a/

b/

Fig. 3. a/ a curved defect; b/ a sharp defect.

3.3. Surface roughness Additive manufacturing of components produces a specific surface in the as-built condition that appears as a high roughness surface. This is due to the fluidic conditions at the front of the melting pools during the laser beam trajectory, which cause droplets of molten material to be stripped off. These fall back onto the surface [11-15] and result in the so-called bailling surface (Fig. 4).

Fig. 4. Left: bailing on the surface with crack(316L); Right: internal and surface defect (AlSi10Mg)

The condition of the surface is important in terms of fatigue crack formation. However, in the case of AM materials, neither the initiation nor the propagation of fatigue cracks are caused by bailing. The critical locations are defects whose notching effect is stronger and these defects occur not only in the internal microstructure but also on the surface of the material. Any additional machining of the material will expose the internal defects on the outer surface. The specific surface roughness after AM production has a more adverse effect on the tribological properties than on the fatigue strength.