## 3 Results and Discussion
### Creep Assessment
#### 3.3.1. Creep Behaviour Assessment--Metallurgical Approach
It could be thus postulated that in general lines, \(\tau_{\text{max}}\) follows similar trends as the net creep depth but in reverse order. According to the comments of [PERSON] et al. [23], this behavior and inter-relation are expected and are exactly associated with the extent of the dislocation mobility the \(\tau_{\text{max}}\) provides. 4. **Stress exponent \(n\)**: Stress exponent \(n\) is an indirect measure of how easily the creep deformation is achieved, and, as a general rule, the higher its values, the more restrained the creep deformation. The stress exponent \(n\), in many cases, dictates the mode and the type of creep behavior [5; 6; 7; 8; 9; 10; 11]. As previously mentioned, in the present effort, the type of creep is a power law creep, which imposes a dislocation glide creep mechanism. The values of \(n\) obtained in the present effort also support this type and are in agreement with other experimental efforts [6; 7; 8; 9; 10; 22]. According to the data of Table 3 and Figure 13, it can be observed that the stress exponent \(n\) is reduced with creep duration time, in general. The second important observation is that the stress exponent \(n\) increases as the preset depth increases. The last important observation is that \(n\) increases as the loading speed decreases, especially in the case of lower loading speeds. As far as the effect of the creep period is concerned, the reduction in time implies that once the primary stage of creep (the stage where the greater portion of the creep deformation is achieved) is met, the creep deformation is not that affected by the applied stress. This is due to the fact that a considerable number of dislocations, as the period increases, are generated that can lead to plastic flow of the material irrespective of the applied stresses. The second effect to be discussed is the effect of the loading speed. It is observed that stress exponent \(n\) increases as the loading speed decreases. This behaviour is associated with the dislocations generated at the initial loading stage. The lower the loading speed, the less the generated dislocations; and the fewer the overall number of dislocations available at the creep stage, the more restricted the deformation they provide, and thus the higher the stress exponent \(n\). Despite these effects, the most important--and obscure, in a sense--is the fact that stress exponent \(n\) increases as the preset depth increases. This trend, as reported in many experimental efforts [7; 8; 9], is a trend mainly associated with FCC high-entropy alloy systems. On the contrary, [PERSON] et al. [9] reported that in the BCC nanocrystalline coatings, the stress exponent remained unaffected by the indentation depth, and recently, [PERSON] et al. [22] reported that stress exponent \(n\) in the MoTaNbvxTi systems they examined was reduced upon increasing the preset depth. It must be mentioned, nevertheless, that during the last effort, the systems consisted of a combination of BCC and HCP phases and not solely of a BCC structure. What also must be mentioned at this point is the fact that the treatment and the discussion of [PERSON] et al. [9] when comparing BCC and FCC structures, are somehow different compared to the present case. [PERSON] et al. [9] compared the BCC structure, which was formed by the addition of Al to a system (Co, Cr, Fe, Ni, and Cu) that, at its equi-atomic composition, possesses FCC structure. In the present effort, the BCC structure is formed solely by BCC refractory metals. The net characteristics between the two BCC structures can be significantly different. The addition of Al creates a more significant lattice distortion, whereas, in the pure BBC refractory high-entropy alloy, the lattice can be undergo further changes. The same trend may occur as far as the stress-elastic strain field within the lattice is concerned. Additionally, lattice defects that can accommodate, incubate, and eventually grow dislocation loops may also be significantly different.