OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 1 2023 Quantitative determination of the amount of wear was carried out by determining the cross-sectional profile of wear tracks according to the standard ASTM G133-05 method. To do this, cross-sectional profiles of wear tracks formed on the surfaces of specimens were reconsrtucted for the as-printed bronze C65500 (Fig. 17, a) and bronze with the addition of aluminum filament (Fig. 17, b) using the software. The obtained profiles confirm the presence of the material deformation and its displacement to the periphery of the wear tracks. The key feature of the formation of burrs is the relationship between its height and the mechanical properties of the specimens. The most ductile and least hard specimens are more severely deformed during friction and the highest burrs are formed on its surface. Harder specimens printed with the addition of aluminum filament are less prone to plastic deformation during sliding friction, and the height of the burrs formed on its surface is 2–3 times less (10–15 µm) than for specimens made of bronze (20–30 µm). a b Fig. 17. Cross-section profiles of the wear tracks of specimens, printed from bronze С65500 (a) and with the addition of aluminum filament (b) In accordance with the standard method, the cross-sectional areas of the wear tracks were determined. It can be observed from Figure 18, that the largest cross-sectional area of the wear track was formed during testing of the annealed specimens of bronze C65500 in accordance with its lowest microhardness. As a result, under conditions of microcontact interaction in a friction pair, its material is easier to deform and wear out. In turn, the use of pre-deformation followed by annealing makes it possible to reduce wear by 15–30% for specimens printed from bronze C65500. This is ensured by a fine structure, which more effectively resists plastic deformation due to the presence of a large number of grain and twin boundaries. Among the specimens printed with the addition of aluminum filament, the highest wear resistance was obtained when intermixing the bronze with the Al-5Si alloy. Its wear is 25% less than that of the most wear-resistant specimen of as-printed bronze C65500. This is due to its high microhardness and mechanical strength. The decrease in wear resistance of alloys printed with the addition of aluminum and Al-12Si is due to its mechanical properties and phase composition. In the first case, the alloy has low ductility and subsurface fracture is more feasible during sliding. In the second case, the addition of Al-12Si to C65500 greatly increases the amount of silicides, which adversely affect the properties of the alloy. During sliding, these fine silicides can be pulled out of the matrix and then act on the surface as abrasive particles, increasing the wear of the bronze surface. In addition, alloys printed with the addition of aluminum filament are less prone to the formation of oxide layers. Because of this, the protective function of the oxide layers is not fulfilled and wear occurs mainly due to the adhesive mechanism. As a result, despite high mechanical properties and microhardness, wear reduction is not so significant.
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