OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 a b Fig. 4. Average values of strength (a) and ductility (b) of coating A: 1 – Oxide layer; 2 – Transition layer; 3 – Metal layer a b Fig. 5. Average values of strength (a) and ductility (b) of coating B: 1 – Oxide layer; 2 – Transition layer; 3 – Metal layer The results of tribological tests of coatings under sliding friction conditions are presented in Figs. 6 and 7. It is shown that the coating of composition A has increased wear resistance compared to the coating of composition B, which also agrees with the data obtained on the values of microhardness and micromechanical properties (see Tables 2–5) [23]. Coating A is characterized by minimum mass loss (~ 1.5 times less than that of coating B) and maximum coefficient of friction (f ~ 0.3). At the initial stage of friction at a load of 30 N there is a run-in period characterized by the highest wear rates (mass loss) and friction coefficients f ~ 0.6 for both coatings. Further, at a load of 75 N, the frictional heating temperature of the friction surface increases, which leads to softening of the scale layer and to a decrease in the friction coefficient f ~ 0.4 for both coatings, which provides an accelerated transition to steady-state wear. At a load of 100–130 N, the steady-state wear on the sliding distance is characterized by almost the same change in mass loss (Fig. 6), as well as close levels of friction coefficient f ~ 0.3–0.4 for coating A and f ~ 0.4 for coating B (Fig. 7 It is worth noting that the temperature of frictional heating of friction surfaces in the case of coating B is lower. It is especially noticeable at friction with loads of 30 and 75 N. The study of wear surfaces of coatings A and B showed that after sliding friction tests at loads of 30 and 75 N, setting processes characterized by detachment of outer coating particles develop (Fig. 8 a, b and
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