PSI - Issue 13

Ali Waqas et al. / Procedia Structural Integrity 13 (2018) 2065–2070 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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3. Results and Discussion

The results of absorbed energy are presented in the following table for specimens in both horizontal and vertical direction.

Table 1. Absorbed energy of sub-size specimen in Charpy impact test and Brinell harness of the specimen.

Absorbed Impact Energy of sub-size sample (J)

Normalized Lateral Expansion (%)

Brinell Hardness (BHN)

Direction

Sample Number

H1 H2 H3 H4 H5 V1 V2 V3 V4 V5

98.5 87.6 98.5 93.9 93.5

46.94 47.32 47.71 43.32 45.32 51.12 52.72 47.88 53.00 49.2

148 152 148 149 149 150 148 149 148 149

Horizontal

91.75 108.1 100.4 110.2

Vertical

99.3

Sample H1 to H5 have been taken from the direction parallel to the deposition direction and are referred as horizontal while V1 to V5 have been taken in the direction perpendicular to the deposition direction and are referred as vertical specimens as presented in Table.1. The average results in horizontal direction is almost 94 J while the average result in vertical direction is approximately 102 J for sub-size samples. Although, additive manufacturing process can result in different behavior and properties in both horizontal and vertical direction due to factors including variations in temperature in successive layers and penetration of molten pool in the previously deposited layer, the difference in both the directions is within 10 % which should not be considered significant. The results indicate homogenous properties in both the directions without any heat treatment process. To further strengthen the homogeneity of obtained structure, metallography has been performed taking the sample larger than the layer height so that transition in structure can be observed if there is any.

Fig. 3. Microstructure attained by an optical microscope (a) 200 µm; (b) 50 µm.

The microstructure as shown in Fig. 3 reveals a uniform structure throughout. As the specimens have been taken from steady stage area, the fusion of layers in this area is so even that variation in layers cannot be judged in the layer build-up direction. So uniform properties are expected in both directions, parallel and perpendicular to the deposition. The average grain size number calculated as per ASTM E112-12 standard is 10.5. The grain refinement is due to the preheat and post heat effect of each successive layer during the welding process thus giving the average hardness of 149 BHN.