PSI - Issue 47

6

P. Ferro et al./ Structural Integrity Procedia 00 (2023) 000–000

P. Ferro et al. / Procedia Structural Integrity 47 (2023) 535–544

540

Fig. 5. Images of IN718 powder: SEM micrograph and b) Vickers hardness indentations

Table 3. EDS analysis of the IN718 particle shown in Fig. 5a C O Al Si Ti

Cr

Fe

Ni

Nb

Mo

7.83 4.02 4.43 1.17

1 2 3 4

12.58 12.23 12.70 44.27

5.95 5.41 5.43

0.31 0.35 0.34 0.11

0.40 0.33 0.36 0.99

0.91 0.71 0.74 0.28

15.05 15.98 16.16

13.30 16.36 15.38

40.16 41.78 41.99 17.32

3.48 2.84 2.45 0.85

21.28

7.10

6.56

3.2. Bi-metallic parts’ characterization As expected, after debinding and sintering heat treatment, the parts underwent a consistent volume and mass reduction (Table 4).

Table 4. Mass before and after the heat treatment Sample Mass of green part [g]

Mass of sintered part [g]

‘Left-right’ ‘Top-bottom’

6.024 5.589

5.018 4.644

Crossed

5.767

4.901

Moreover, geometric models measured by 3D scanner highlight some distortions in heat-treated parts (Fig. 6), due to both a non-optimal heating ramp and the absence of the steel blend around the sample. Macrographs of the FDMS parts are shown in Figs. 7 and 8. It is observed a high amount of porosity concentrated in the HCS zones due to a lack or partial sintering of the steel powder. This suggests that the sintering process parameters in bi-metallic components is limited by the more-demanding alloy in term of temperature and time. Moreover, the particle size plays a fundamental role in the sintering parameters (say, temperature and time) that needs to be carefully investigated and taken into account in future trials. Because of the failed sintering treatment, it was considered useless to evaluate the degree of porosity but rather the focus was on the microstructural features of the powders and the interface.