## 3 Results and Discussion
### Creep Assessment
#### 3.3.1. Creep Behaviour Assessment--Metallurgical Approach
Similar observations can also be found in other experimental efforts [8; 9; 22]. The second important outcome is the fact that the higher the preset depth, the higher the creep deformation, which is particularly profound during the prolonged creep stage (30 s). On the contrary, for the short creep duration (10 s), it can be seen from Table 3 and Figure 11 that there is no significant alteration in creep deformation for a given loading speed. The answer behind this behavior is based on the type of the relation, h\({}_{creep}\) versus time. As previously mentioned, the fitting parameters used to show an exceptional correlation suggest the presence of a power law creep, which is mostly associated with dislocation glide mechanisms [2; 4; 5; 9; 11; 12; 34]. During this mode of deformation, creep displacement  
Figure 14: The effect of the different testing parameters on the critical volume for dislocation nucleation (Vcr). is significantly high at the initial periods of the creep stage and gradually reduces. As such, during the first 10 s, the highest proportion of the overall creep deformation is obtained, which seems to be a common behavior for all the different preset depths. For the more prolonged creep duration, however (30 s), the situation is altered and, as already stated, the preset depth seems to affect the net creep displacement. In this case, the parameter that is activated is the volume underneath the indenter that is plastically deformed. According to [PERSON] [4], the higher the indentation depth, the more expanded this plastically deformed zone. Since this zone is expanded and in conjunction with the fact that the time is considerably increased, the mobile dislocations within this zone, can move more extensively to provide plastic deformation. [PERSON] et al. [22] and [2; 5; 9; 11; 12; 34] also reported similar observations concerning the effect of the preset depth. The third point to be discussed is the effect of the loading speed at the loading stage prior to the net creep stage. It can be seen from Table 3 that as the loading speed decreases, the creep deformation decreases. This behaviour is most likely (a) associated with the number of dislocations being generated at the loading stage. At low loading speeds (i.e., low strain rate), the rate of dislocation generation is reduced, a fact that has a direct impact on the number of available mobile dislocations that could accommodate the plastic deformation; (b) the expression of micro-creep phenomena prior to the net creep stage. If we recall the loading stage presented in Figures 7-9, it was observed that at low preset depths and lower loading speeds, the presence of serrations was traced. Serrations indicated micro-creep phenomena at the loading stage, and this premature micro- creep drains the creep deformation that could be expressed at the net creep stage. These observations agree with other research efforts [5; 6; 7; 8; 9; 10; 11; 22; 23]. 3. For a more thorough assessment of creep behavior, it is important to take into consideration other parameters in addition to the net creep deformation obtained from the previous paragraphs. **Maximum shear stress (\(\tau_{\text{max}}\)): \(\tau_{\text{max}}\)** is the stress that practically drives the deformation process since it is the stress that makes the dislocation move and provide the plastic flow of the material. It can be seen from the data of Table 3 and Figure 12 that \(\tau_{\text{max}}\) decreases, in general, as the preset depth increases. This is expected since, according to the calculation sequence, \(\tau_{\text{max}}\) is directly related to the hardness, which, as shown and explained previously, is also reduced as the indentation depth increases. What is significant is that this trend is more profound for the lower creep periods (10 s). Additionally, it appears that \(\tau_{\text{max}}\) is also slightly affected by the loading speed, with this effect being more significant for the lower preset depths.