PSI - Issue 14

6

Anigani Sudarshan Reddy et al. / Procedia Structural Integrity 14 (2019) 449–466 Author name / Structural Integrity Procedia 00 (2018) 000–000

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Table 5: List of etchants used for this study

S.No

Material

Etchant used

1 2 3 4 5 6 7

DMLS IN718 DMLS CoCrMo

Acetic glyceregia

5%HCl electrolytic, 5V, 4sec. 10% HNO3 solution for 10 sec

DMLS Maraging steel

DMLS SS316L DMLS Ti6Al4V Cast FSX-414 Forged X20Cr13

Glyceregia

Keller’s reagent

5%HCl electrolytic, 5V, 4sec.

2% Nital solution

Thickness‐0.5 mm

a

c

d

b

Fig. 2. Schematic showing the orientation of small scale tensile test specimens in (a) Monolithic DMLS samples, (b) Hybrid DMLS sample and the substrate, (c) Micro tensile specimen dimensions and (d) Regular tensile specimen 3. Results and Discussion 3.1. Microstructural characterization of monolithic DMLS Alloys Figure 3 (a, c, e, g, i) shows representative scanning electron micrographs of the starting powders of the five alloys IN718, CoCrMo, Maraging steel, SS316L, Ti6Al4V, respectively. A nearly spherical morphology can be seen for all the alloys, with a particle size distribution and average particle size of 11-84 µm and 34 µm for (IN718), 14-76 µm and 33 µm for (CoCrMo), 16-76 µm and 37 µm for (Maraging steel), 14-76 µm and 33 µm for (SS316L) and 14-86 µm and 37 µm for (Ti6Al4V), as shown in Figure 3(b, d, f, h, j) respectively. The average powder particle size was nearly the same in all the cases, between 33-38 µm. The as printed part porosity is a critical parameter for the final properties and performance of the DMLS alloys. All the samples investigated in present the study were produced with minimal porosity having a density more than 99.5% without any Hot Isostatic Pressing (HIP) by using optimized process parameters. Figure 4 (a-e) shows representative micrographs taken along the build direction. It can be seen that there is little or no porosity in all the five DMLS alloys.