PSI - Issue 53

S. Senol et al. / Procedia Structural Integrity 53 (2024) 12–28

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

total measurement uncertainty (Fitzpatrick et al., 2002), the residual stress states for AB and R samples are considered to be comparable. On the other hand, the tensile residual stresses decrease considerably in the cases of the ‘PW laser processed’ (61 MPa), EDM (-14 MPa), and M (-136 MPa) samples, suggesting that compressive stresses are introduced on these samples during the respective surface treatments, the most considerable one in this study, being the milling. The full stress tensor can be found in Appendix B. Fig. 4 displays the 3D reconstructions of representative 3PBF samples for each surface condition, focusing on the curved regions. As high density is recorded for all conditions, with no large internal pores or defects, the stair case effect and roughest surface can clearly be observed in the AB state (Fig. 4(a)), as well as the smoother surfaces achieved for R, EDM, and M conditions as visualized in Fig. 4(b), (c), and (d), respectively.

Fig. 4. 3D reconstructions of µCT scans displaying the dense 3PBF samples with different surface conditions; (a) AB, (b) R, c) EDM, and d) M. The XZ and YZ cross sections shown by µCT slices, respectively, for AB (e, i), R (f, j), EDM (g, k), and M (h, l) conditions.

In addition, the microstructure of the etched YZ cross sections is visualized for each condition by OM imaging (Fig. 5). Firstly, in Fig. 5(a), the AB microstructure with randomly distributed B 4 C particles and Ti-rich regions, as well as the rough surface and some spatters can be seen. In Fig. 5(b), it can be noticed that re-melted surface of dL PBF processed (R) samples has noticeable ~200 µm melt-pool depth, indicating the depth of heat affected zone for R samples and suggesting that deeper melt-pools are formed for the re-melted layer as a result of higher energy density used, as compared to the bulk. Furthermore, in Fig. 5(c), the ‘white layer’ with a thickness of 10 to 20 µm at the EDM surface is revealed, while the rest of the microstructure is comparable to the AB sample. Finally, for milled (M) samples, an unaltered microstructure with a very smooth top surface is presented in Fig 5(d).