PSI - Issue 38

Christophe Grosjean et al. / Procedia Structural Integrity 38 (2022) 94–108 C.Grosjean and al. / Structural Integrity Procedia 00 (2021) 000 – 000

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5

a

b

c

d

Fig. 3. (a) Part produced by MBJ. A global deformation is observed. (b) Deformation in the channel. (c) Metallography exam without etching and (d) after etching.

A measurement of the porosity rate by image analysis was carried out. The measured rate is 0.7% with an average pore size of 16µm for the equivalent diameter and a value of 54µm for the largest (see Fig. 3(c)) . After etching, the structure is mostly martensitic with a delta ferrite network (see Fig. 3(d)) . Mechanical properties were measured and show that the yield strength (Rp0,2) is significantly lower in the vertical direction compared to the horizontal direction (see Table 2). Table 2. Mechanical properties of 17-4PH produced by MBJ on an ExOne R2 machine after a heat treatment (Annealing 1030°C 1h + ageing 480°C 2h). Average over 2 samples.

R m [MPa] R p0.2 [MPa] A%

Z%

E [GPa]

Horizontal 1243

1069

15,3 42,0 192 14,5 37,0 190

Vertical

1220

634

4.3. LWC production and characterization LWC is a more widespread and mature process than AM. The heat treatment performed is different from other processes with a modified ageing temperature of 610°C. A wax model is produced using a polymer AM machine. This wax model is then assembled with others to create a wax tree. A multi-layered ceramic shell is added around it by immersing the wax tree in a slip several times and then drying it. Due to the constraints of filling the mold, the geometry of the hydraulic block was modified by simplifying the attachment area (see Fig. 4). Additional machining was then necessary. The weight was slightly increased by about 15%. The parts were subcontracted to the Fonderie Lajoinie who gave typical values of mechanical resistance on this alloy R m = 990 MPa, R p0,2 = 885 MPa and A% = 14.5%.