## 3 Results and Discussion
### Hardness Analysis  
The mechanical properties of all the seven main parts were evaluated in terms of Vickers microhardness at room temperature, as represented in Figure 7. For comparison, the hardness value of the wrought IN718 [based on the AMS 5663, [72] and cast IN718 [based on the AMS 5383 [73]] are also presented in the same figure. To evaluate the effect of support type on the hardness, the angled-type of support (AT53G80), cone type support (CT53G80), and pin type support (PT53G80) were compared. From Figure 7, as the lattice parameter decreased, the hardness of the samples increased for the samples fabricated with different types of support. The PT53G80 sample resulted in the highest hardness of 460.5 HV, while the AT53G80 and CT53G80 support yielded a hardness value of 354.6 HV and 341.6 HV, respectively. This can be attributed to the different levels of secondary phases and precipitations explained in Section 3.1. It has been reported that the hardness of the IN718 alloy is dependent on the precipitation of two main secondary phases, \(\gamma^{\prime\prime}\) and \(\gamma^{\prime}\) \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{4}{c}{**Elements**} \\ \cline{2-5}  & **Ni** & **Cr** & **Fe** & **Ti** \\ \hline AT53G80 & 46.1 & 17.6 & 16.1 & 1.0 \\ CT53G80 & 52.9 & 23.6 & 20.8 & 2.5 \\ PT53G80 & 57.3 & 21.1 & 20.3 & 1.2 \\ AT33G80 & 50.3 & 19.4 & 17.4 & 1.1 \\ AT80G80 & 44.8 & 16.3 & 14.2 & 1.2 \\ AT33G100 & 54.6 & 20.4 & 18.5 & 1.2 \\ AT60G100 & 54.5 & 20.6 & 18.5 & 1.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: EDS analysis showing chemical compositions at the core of columnar dendrites of LPBF-processed Inconel 718 parts fabricated using different support structures. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **Top Area (mm2)** & **Bottom Area (mm2)** & **Support Volume(mm3)** \\ \hline AT53G80 & 28.18 & 40.77 & 120.46 \\ CT53G80 & 11.30 & 40.77 & 115.49 \\ PT53G80 & 10.08 & 40.77 & 113.11 \\ AT33G80 & 16.87 & 33.20 & 92.43 \\ AT80G80 & 38.69 & 48.00 & 142.63 \\ AT33G100 & 12.97 & 27.76 & 81.10 \\ AT60G100 & 28.00 & 39.00 & 115.11 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The top area, bottom area, and support volume for different support structures. phases [74]. Another study conducted by [PERSON] et al. demonstrated that the \(\gamma^{\prime}\) phase had a more significant role in the hardness of the as-fabricated IN718 [36]. In a similar study, [PERSON] et al. [75] stated that a reduction in the strengthening phase leads to lower values of Vickers hardness. In agreement with the literature, the sample fabricated on top of the pin-type support structure (PT53G80) had a higher portion of secondary phases resulted in a higher hardness value. Moreover, the significant increase in hardness for this sample can be attributed to the crystal and grain size of the main part. As mentioned in Section 3.1, due to the broader and shallower diffraction peak observed for the sample with PT53G80 support, finer grain size can be inferred based on the Scherrer equation [76]. Also, based on the Hall-Petch equation, there is an inverse relationship between the hardness and grain size [77], which explains the highest level of hardness for the sample with finer grain size supported by PT53G80. However, since some other factors such as the condition of distribution of \(\gamma^{\prime}\) particles and the size of this strengthening phase can also affect the hardness of IN718 alloy, more investigation is needed to find the exact phenomenon that resulted in a significant rise in the hardness of this sample. In terms of geometrical parameters, a similar effect can be observed in the thickness variation for the supports. The sample fabricated with lower thickness support (AT33G80) showed a higher hardness value compared to the one fabricated with thicker support (AT80G80), due to the difference in level of precipitates discussed. The same trend was seen for samples with AT33G100 and AT60G100.