## 3 Results and Discussion
### Microstructural Analysis  
The SEM micrographs of the IN718 parts are presented in Figure 8. Figure 9 represents the results of the dimensional analysis performed on melt pool size for all the samples,  
Figure 7: Vickers hardness evaluation of the LPBF-processed samples fabricated on top of support structures with different type and geometry. As reference, the Vickers hardness values of wrought IN718 (AMS 5663 [72]) and cast IN718 (AMS 5383 [73]) are also reported.  
with the depth of melt pools being calculated. Regardless of the variation in size, the average depth of the pools was found higher than the initial layer thickness for all the samples. This proves the overlapping of laser tracks resulting in overlapping of melt pools, which has been reported as one of the thermal behaviors of the LPBF technique [79, 80, 81]. According to the results, the pin-type (PT53G80) gives rise to the highest average melt pool depth of ~79.1 \(\upmu\)m followed by cone-type (CT53G80) to ~71 \(\upmu\)m. However, the angled-type (AT53G80) showed the lowest average melt pool depth of ~62 \(\upmu\)m in the fabricated sample. Therefore, as the contact area between the main part and the supports increased, shallower pools formed in the sample. This can be again attributed to the different thermal conditions and heat transfer rate experienced by the sample caused by different types of support used. A higher contact area between the main sample and support (see Table 3) facilitates heat dissipation through conduction and therefore faster solidification and less time for the molten material to penetrate into the deeper layers. This condition underwent by the sample with angled-type support causes the formation of shallower pools. Conversely, less contact area for the sample fabricated with pin-type support provides a better condition for flowing the molten material into underneath layers, re-melting these layers, and the overlapping of pools. This led to the formation of deeper pools in the microstructure of the sample. The observation is in agreement with previous studies where the formation of deeper pools was attributed to the numerous reheating cycles and laser overlapping [69]. It also has been reported that overlap between the melt pools associates with reheating cycles which acts similar to the heat treatment process. This causes more evenly dispersion of fine \(\gamma^{\prime\prime}\) particles in the matrix [15, 32, 70] which improves the hardness value. This is consistent with the higher hardness value observed for the sample fabricated on pin-type support, with deeper pools being revealed in its microstructure. When it comes to the effect of geometrical parameters on the melt pool dimensions, the influence of thickness can be observed by comparing samples supported by AT80G80 and AT33G80, and also AT33G100 and AT60G100. A slight increase in depth of the pools can be seen for AT33G80 compared to AT80G80, and AT33G100 as against AT60G100. As expected, depth of the pools is higher for samples fabricated with a lower thickness value (i.e., less contact area). Therefore, it is consistent with the logic discussed for the different types of supports. Comparing the pool depth of the samples supported by AT33G80 and AT33G100 revealed that the gap value didn't affect the dimension of pools considerably.