## 3 Results and Discussion
### Nanoindentation-Based Basic Mechanical Property Assessment  
#### 3.2.1 Obtained Data and Metallurgical-Microstructural Evaluation  
Table 1 summarizes the results concerning the calculation of the standard mechanical properties, i.e., hardness (HV), modulus of elasticity (Eit), and the energy absorbed in the elastic area over the overall absorbed energy (nit). It must be mentioned that the values in Table 1 are given directly by the software of the nanoindentation apparatus and are based on the approach of Oliver-Pharr [26; 27]. It must be mentioned that in Table 1, the designation input and outcome variables are reported, which is important for the correlation analysis that is demonstrated in the following paragraphs. Graphical representations of Table 1 data are presented in Figures 1-3. More specifically, Figure 1 shows the effect of the preset depth and the loading speed on the indentation hardness H\({}_{\text{it}}\), Figure 2 shows the corresponding effect on the indentation modulus of elasticity E\({}_{\text{it}}\), and Figure 3 presents the effects on the absorbed elastic energy n\({}_{\text{it}}\). 1. The indentation hardness values lie within a broad range of roughly 800-1000 HV and are, in general, in good agreement with other experimental efforts dealing with this refractory high-entropy alloy [25]. The two different input parameters, i.e., preset depth and loading speed, seem to have, in general, the opposite effect: the higher the preset depth, the lower the hardness values, whereas the lower the loading speed, the higher the hardness. Concerning the effect of the preset depth, the observed trend is expected since (a) according to the Oliver-Pharr approach [26; 27], the contribution of the load \(P\) and the indentation depth h in calculating the hardness is not analogous (hardness is a function of \(P/h^{2}\)), and as such, as the indentation depth increases, the hardness values decrease; (b) furthermore, if we recall that hardness is practically the resistance to plastic deformation, the observed trend shows that at higher indentation depths, the plastic deformation can be expressed more easily. This is attributed to the fact that at higher indentation depths, the affected material volume underneath the indenter increases, which implies that the number of dislocations to accommodate the plastic deformation increases, which, in this way, increases the capability for the plastic flow to be expressed. The effect of the loading speed, as already stated, is, in general, the opposite. Hardness values decrease as the loading speed increases. It must be mentioned, however, that the effect of the loading speed is not as severe as the effect of the indentation depth. The trend concerning the effect of the loading speed is also associated with the availability for plastic deformation dislocations. As the loading speed increases, the rate of dislocation generation increases, ensuring that there are enough dislocations to contribute to the plastic flow of the alloy. The effect is more profound at lower indentation depths and seems to fade as the indentation depths increase. This is attributed to the fact that the affected material volume where dislocations can generate increases, and this increase gradually compensates for the restriction of dislocations at the lower depths.