OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 Fig. 8. Coating A surfaces after sliding friction tests: a – load 30 N; b – load 75 N; c – load 100 N; d – load 130 N а b c d Fig. 9 a, b). With increasing load (100 and 130 N), when the oxide layer is almost completely worn out, the metal layer of the coatings of compositions A and B provides the transition to wear by the mechanism of plastic displacement (Fig. 8 c, d and Fig. 9 c, d), which corresponds to a decrease in the magnitude of wear. The study of the chemical composition of the wear surfaces showed that at all selected test loads under sliding friction conditions the inner layers of both compositions were preserved at a maximum load of 130 N (Tables 6 and 7). This confirms the purpose of these layers to prevent tool fracture, which allows timely restoration of wearied outer layers. The results of studies of surface roughness of coatings A and B showed that after sliding friction tests there is a smoothing of the initial surface roughness and a decrease in the value of the arithmetic mean deviation of the profile Ra. The minimum values of the arithmetic mean deviation of the Ra profile are observed after a load of 30 N (Ra = 0.434 μm for coating A and Ra = 0.99 μm for coating B), where the wear of the surface oxide layer, which plays the role of lubrication, occurs. As the sliding friction load increases from 75 N to 130 N, the average Ra value increases (see Fig. 10 c–e and Fig. 11 c–e). Analysis of the surface micro-profile taken during 3D profilometry showed that after friction with 30 and 75 N load, isolated depressions related to the setting processes were observed (Fig. 10 b, c and Fig. 11 b, c shown by arrows). The surfaces after friction with a load of 100 and 130 N (Fig. 10 d, e and Fig. 11 d, e) are characterized by the presence of unidirectional protrusions and depressions. Higher values of roughness parameter Ra for coating B after sliding friction tests are characterized by the presence of more oxides on the surface (see Tables 6 and 7). As a result of the research, it was found that the tribological properties of the studied coatings depend on the chemical composition of the sprayed material and the resulting strengthening phases.
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