## 3 Results and Discussion
To assess the nature of coating wear and to establish the relationship between the temperature regime and the degree of surface damage, three-dimensional topographic images and cross-sectional profiles of wear tracks were obtained after tribological tests at temperatures of 21 \({}^{\circ}\)C, 450 \({}^{\circ}\)C, 550 \({}^{\circ}\)C, and 650 \({}^{\circ}\)C (Figure 8). At room temperature (21 \({}^{\circ}\)C), the widest and deepest wear track with a maximum depth of up to \(\sim\)80 \(\upmu\)m is observed (Figure 8a,e). Wear is characterized by significant plastic deformation and the absence of signs of self-organization or the formation of protective layers. Irregularities and pronounced defects along the profile edges indicate an unstable friction regime and intense abrasive action. At 450 \({}^{\circ}\)C, a distinct concave wear track with pronounced irregularities along the edges and noticeable asymmetry in width can be observed on the wear surface topography (Figure 8b,f). The wear depth reaches approximately 60 \(\upmu\)m, and the track width is significantly narrower compared to wear at room temperature. On the side sections, areas with increased roughness are visualized, which may indicate partial microchipping [45]. The central part of the profile demonstrates a deepening characteristic of plastic deformation under conditions of initial softening of the coating. The most favorable nature of wear is observed at a temperature of 550 \({}^{\circ}\)C (Figure 8c,g). Three-dimensional surface topography shows a uniformly formed wear track with a small depth of no more than \(\sim\)20 \(\upmu\)m. The transverse profile has a smoothed shape with minimal height fluctuations, which indicates a stable friction process. Moderate thermal exposure probably activates the mechanisms of plastic deformation of the upper layers of the coating and promotes the formation of a thin oxide film, which plays the role of a lubricating layer. Such a film reduces contact friction between the surfaces and simultaneously limits the wear intensity. The absence of sharp depressions and deformations in the profile confirms that the destruction of the  
Figure 7: Dependences of the friction coefficient on time (number of cycles) at different temperatures: (a) 21 \({}^{\circ}\)C; (b) 450 \({}^{\circ}\)C; (c) 550 \({}^{\circ}\)C; (d) 650 \({}^{\circ}\)C.  
coating at this temperature occurs mainly by the mechanism of soft oxidative wear, without significant brittle destruction. This also correlates with the minimum value of the friction coefficient recorded at this temperature. At a temperature of 650 \({}^{\circ}\)C, the opposite trend is observed (Figure 8d,h). The wear track becomes deeper, reaching \(\sim\)65-70 \(\upmu\)m, and wider compared to 550 \({}^{\circ}\)C. The surface topography shows a symmetrical concave track shape with clearly defined edge zones, indicating increased brittle destruction of the coating material. The transverse profile demonstrates a significant deepening with sharp height differences, which may be associated with the degradation of the previously formed oxide film and the activation of intense oxidation processes. At high temperatures, a loose and non-adhesive oxide phase can form, which does not provide protection against friction, but on the contrary, contributes to its growth. Figure 9 shows the analysis results of the wear of sample No. 1 obtained during tribological tests in the temperature range from 21 \({}^{\circ}\)C to 650 \({}^{\circ}\)C. The diagram reflects changes in the volumetric wear of the sample, volumetric wear of the ball, and mass wear of the sample depending on the test temperature.