OBRABOTKAMETALLOV technology Vol. 27 No. 2 2025 In this case, a significant portion of the energy generated by bubble collapse is transferred to the abrasive particles, which, upon impacting the surface, perform micro-cutting. This redistribution of energy changes the nature of the treatment towards a predominantly mechanical abrasive process. After one minute of CAT, a significant portion of the spheres is removed. The formation of sites characteristic of both CT and CET+CT is almost imperceptible. This suggests that defects with poor adhesion are preferentially removed first due to the impact of the abrasive. Further, the effect of CET+CT is that CT etches defects, reducing the strength of their adhesion to the surface, after which they are removed by the abrasive. Defects with high adhesion strength, primarily those resulting from spheroidization, deform upon impact of the abrasive, leading to a reduction in the height of the relief irregularities. As a result, after 10 minutes of treatment with CAT, the surface consists of significantly deformed spheres and melting tracks, also exhibiting traces of abrasive action. The mechanism of ultrasonic SPD involves the plastic deformation of surface irregularities (Fig. 10). Under the action of a force applied normally to the surface, the protrusions of irregularities deform. The height of the spheres decreases with the formation of a flattened area, while they simultaneously grow in width and begin to touch other spheres. Consequently, deformed areas of a sufficiently large size are formed on the surface. With continued treatment, the spheres located below begin to deform, and the area of the deformed regions increases. The largest area is achieved after approximately 10 seconds of treatment. As the treatment time increases further, no significant changes occur, likely due to the achievement of the maximum degree of deformation. Despite the significant effect of surface smoothing, treatment of microrelief depressions is not achievable with this method, as illustrated in all the photos. Despite the significant effect of surface smoothing, treatment of microrelief depressions is not available for this method, which is illustrated in all the photos. The analysis of microstructure changes is presented below. Analysis of surface roughness changes The surface changes resulting from the considered treatment methods lead to change in surface roughness. Profilometer traces, each 2.5 mm long, and height roughness parameters for all treatment types are presented in Table 2. Рис. 10. Dynamics of surface changes during ultrasonic SPD
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