PSI - Issue 53

Sunil Raghavendra et al. / Procedia Structural Integrity 53 (2024) 119–128 Author name / Structural Integrity Procedia 00 (2019) 000–000

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layer was used in the deposition process, with an overlap of 50% of the track width between the tracks. The deposition pattern in specimens 1 and 2, the laser power was decreased by 100 W for each layer, with the minimum laser power of 1700 W used for the top two layers. While for specimens 3 and 4, all five layers were deposited using 2000 W of laser power. Additionally, two different carrier gas flow rates were used for the deposition, as indicated in Table 2. A schematic of the top view of the multiple tracks is shown in Fig 2(a), the cross-section in Fig 2(b), and the pins extracted for the Pin-on-Disc test in Fig. 2(c),

Table 3 DED process parameters for multi-layer deposition

Scanning speed (mm/min)

Carrier gas flow rate (L/min)

Laser power (W)

Feed rate (g/min)

Laser power variation Decreasing Decreasing

Spec No

No. of Layers

1 2 3 4

2000 2000 2000 2000

8 8 8 8

800 800 800 800

5 5 5 5

4.5

6

4.5

Constant Constant

6

Figure 2 Schematic diagram of (a) top view of the deposition (b) cross-section of the multi-layer deposition and (c) cylindrical pins extracted for the Pin-on-Disc test

2.3. Porosity, microhardness and microstructure The characterization was carried out to evaluate the deposition quality obtained from the DED process for single track and multiple-layer specimens. 2.3.1. Porosity It has been determined that the DED process parameters impact the pores within the samples. Therefore, to gain insights into how these parameters affect porosity, the cross-sections of single-track and multi-layer depositions were analysed. The specimens underwent a series of steps, including cutting, mounting, and polishing, using SiC abrasive papers with grit sizes ranging from 500 to 4000. Subsequently, the specimens were polished on cloth using diamond suspension solutions with particle sizes of 3 µm and 1 µm. Comprehensive images of the specimens were captured using a light optical microscope (LOM) and stereomicroscope in the case of multi-layered pins and subjected to analysis using ImageJ®. The percentage of porosity within the specimens was determined using Equation 1. ��������� ∑���� �� ����� ����� ���� � 100 (1)