## 3 Results
Figure 4: Nature of T2 coating destruction during scratch test: end of scribing groove (**a**), nature of coating destruction (**b–d**). Figure 5: Nature of T7 coating destruction during scratch test: end of scribing groove (**a**), nature of coating destruction (**b–d**). For cutting out the lamellae, areas on the border of the scribing groove were selected (Figure 7). These areas allow us not only to study the structure of the coatings, but also provide an opportunity to study the nature of the destruction of the coating and adjacent layers of the substrate under the influence of the movement of the indenter during the scratch test. The study of the interface region of the T2 coating and the substrate reveals a complex, multilayered structure of this region (Figure 8a). As a result of the SAED phase analysis (Figure 8b) and the analysis of the change in the elemental composition (Figure 8c,d), three regions can be distinguished:  
Figure 6: Nature of T12 coating destruction during scratch test: end of scribing groove (**a**), nature of coating destruction (**b–d**). **A. ** The coating region in which the hexagonal phase based on aluminum nitride (Al,Ti)N B4 dominates, but a cubic phase based on titanium nitride (Ti,Al)N B1 is also present. **B. ** The nitrided layer [46; 47; 48; 49; 50] of the titanium substrate with a significant diffusion of aluminum, in which the phases (Al,Ti)N B4 and (Ti,Al)N B1 are also present. This layer differs significantly in crystal structure from the next layer of the titanium substrate. These changes in the elemental composition indicate that the diffusion of aluminum into this layer is uneven; the aluminum content is in the range from 0.5 to 17.0 at.%. The presence of reflections of the (Al,Ti)N B4 phase can be explained by the fact that since this layer is quite thin (about 250 nm), the SAED analysis also captures the (Al,Ti)N layer located above with the selector diaphragm, as well as the presence of a certain amount of diffused aluminum in the B layer itself. A distinctive feature of this layer is also a significant decrease in the grain size (down to the nanometer) compared to the titanium substrate. Of particular interest is the fact of the nitriding of this layer with a flow of gas (nitrogen) plasma during the preliminary etching of the samples. Figure 8: Study of the structure and elemental and phase composition of the T2 coating: structure of the coating–substrate interface (**a**), phase composition of the coating and adjacent substrate layers (SAED) (**b**), change in elemental composition in the coating–substrate interface region (**c**,**d**). **C.** An unmodified layer of the titanium substrate with the dominant Ti A3 phase. Between layers A and B, a thin (10-20 nm) light-contrast layer can be seen, which may be formed by residual titanium oxide (precise identification is impossible due to the low thickness of this layer) [51; 52; 53]. A crack can also be seen that turns into a delamination between the titanium substrate (C) and the nitrided layer with aluminum diffusion (B). This crack was formed as a result of the action of the indenter during the scratch test, and it is worth noting that the delamination did not occur between the coating and the substrate, but between two layers of the substrate. The study of the coating-substrate interface structure in sample T7 shows that a strong adhesive bond is maintained between them (Figure 9a). Directly at the boundary of the coating and the substrate, a layer of grains 3-10 nm in size is observed, possibly residual titanium oxide (an accurate determination of the composition is impossible due to the small grain sizes) (Figure 9b). Figure 9: Coating–substrate interface structure (**a**), grain layer at coating–substrate interface (**b**), study of elemental (**c**) and phase composition (**d**) of T7 coating. In the T7 coating, the cubic phase (Ti,Al)N B1 is dominant (Figure 9d), and no hexagonal phase based on aluminum nitride is observed, which may indicate the complete dissolution of aluminum in the TiN structure.