## 3 Results and Discussion
### Thermal Stability under Nanoindentation  
The temperature dependence of hardness and compressive stresses for Ta-Zr-Si-B-C and Ta-Zr-Si-B-N coatings is presented in Table 1.  
In the case of Ta-Zr-Si-B-C coating, the temperature increase from 20 to 1000 \({}^{\circ}\)C led to a decrease in E by 8%, in W by 25% and in the parameters H/E and H\({}^{3}\)/E\({}^{2}\) by 30 and 70%, respectively. For the Ta-Zr-Si-B-N coating, an increase in temperature from 20 to 1000 \({}^{\circ}\)C was accompanied by an increase in E from 229 to 275 GPa, in W from 74 to 77% and in H\({}^{3}\)/E\({}^{2}\) from 0.232 to 0.260 GPa. The H/E parameter decreased slightly with an increase in temperature from 20 to 1000 \({}^{\circ}\)C.  
Figure 11: XPS spectra of Ta4f (**a**), Si2p (**b**) and N1s (**c**) for Ta-Zr-Si-B-N coatings after vacuum annealing at temperatures of 600, 800 and 1000 \({}^{\circ}\)C.  
For the Ta-Zr-Si-B-C coating, an increase in temperature from 20 to 1000 \({}^{\circ}\)C was accompanied by a gradual decrease in hardness from 25 to 16 GPa and in the level of internal stresses from \(-1.1\) to 0 GPa (Figure 12a). A decrease in internal stresses during thermal exposure may be associated with the ordering of the coating structure and the crystallization process [50,51]. A decrease in the hardness of the Ta-Zr-Si-B-C coating by 36% may be associated with stress relaxation during thermal exposure, by analogy with [52]. When the Ta-Zr-Si-B-N coating was heated to 200 \({}^{\circ}\)C, the hardness increased slightly from 23 to 24 GPa; in the range of 200-800 \({}^{\circ}\)C, the values stabilized at -25 GPa, which is explained by a minimal change in the level of internal stresses (Figure 12b). The absence of a change in \(\sigma\) is due to the absence of structural changes and phase transformations in the coating at temperatures of 20-800 \({}^{\circ}\)C. At 1000 \({}^{\circ}\)C, stress relaxation was observed, associated with the pronounced crystallization of the coatings. The abrupt rise in hardness to 27 GPa at 1000 \({}^{\circ}\)C cannot be explained by high internal stresses, since \(\sigma\) = 0 GPa at this temperature, and is most likely associated with the beginning of the crystallization process and the release of h-Ta\({}_{5}\)Si\({}_{3}\) and c-TaN phases. Thus, for the Ta-Zr-Si-B-C coating, a clear correlation was observed between the decrease in the level of residual stresses and the decrease in hardness with increasing temperature. The processes of structure ordering and crystallization occurring at temperatures of 600-1000 \({}^{\circ}\)C in the Ta-Zr-Si-B-C coating seem to have a negative effect on the level of mechanical properties. For the Ta-Zr-Si-B-N coating, the influence of crystallization prevails. A similar effect of crystallization on the mechanical properties was revealed for Ta-Si-N coatings [53]: the hardness of the coatings increased from 17 to 21 GPa with an \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline  & & & \multicolumn{4}{c}{**Coating Ta-Zr-Si-B-C**} & \multicolumn{4}{c}{**Coating Ta-Zr-Si-B-N**} \\ \cline{2-13}
**T**, \({}^{\circ}\)**C** & **H**, **GPa** & **E**, **GPa** & **W**, \%** & \(\sigma\)**, **GPa** & **H/E** & **H\({}^{3}\)/E\({}^{2}\)** & **H**, **GPa** & **E**, **GPa** & **W**, \%** & \(\sigma\)**, **GPa** & **H/E** & **H\({}^{3}\)/E\({}^{2}\)**, \({}^{4}\)** \\  & & & & & & & & & & & & & \\
20 & 25 & 259 & 71 & \(-1.1\) & 0.096 & 0.233 & 23 & 229 & 74 & \(-1.1\) & 0.100 & 0.232 \\
200 & 27 & 277 & 80 & \(-0.7\) & 0.097 & 0.256 & 24 & 241 & 75 & \(-1.3\) & 0.099 & 0.238 \\
400 & 23 & 250 & 70 & \(-0.6\) & 0.092 & 0.195 & 25 & 245 & 78 & \(-1.4\) & 0.102 & 0.260 \\
600 & 24 & 281 & 72 & \(-0.6\) & 0.085 & 0.175 & 25 & 252 & 74 & \(-1.3\) & 0.099 & 0.246 \\
800 & 21 & 273 & 67 & 0 & 0.077 & 0.124 & 25 & 259 & 72 & \(-1.2\) & 0.096 & 0.233 \\
1000 & 16 & 239 & 53 & 0 & 0.067 & 0.072 & 27 & 275 & 77 & 0 & 0.098 & 0.260 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Mechanical characteristics of coatings depending on temperature.