OBRABOTKAMETALLOV Vol. 27 No. 2 2025 technology Fig. 3. Boron carbide particles their continuous circulation within that volume and return to the cavitation treatment zone. Boron carbide powder B4C was used as an abrasive (Fig. 3), chosen for its high hardness and resistance to chemical attack. The abrasive powder was added to a level above the treated surface, with a volume concentration of 20%. After the ultrasound was activated, the abrasive was distributed throughout the volume by the acoustic streaming. To minimize the thermal effects during ultrasonic treatment, a glass container holding an etching solution was placed in a large container with water at room temperature of 20 °C. The treatment was interrupted at intervals of 1 to 3 minutes to photograph surface changes. Ultrasonic SPD was performed by pressing the end of the oscillatory system against the sample under its own weight P =70 N (Fig. 4). The treatment was carried out for 10 seconds while photographing the surface every 2 seconds. Comparison of surface treatment mechanisms in CET and CAT To compare the impact mechanisms on the surface during CET and CAT, high-speed photography of the metal plate treatment in water was performed. The metal plate was also positioned at a distance of 20 mm from the end of the radiator. The photography was performed using a Fastec Hispec camera, capable of recording video clips at frame rate ranging from 500 to 112,000 fps. To analyze the movement patterns of cavitation bubbles and abrasive particles over the treated surface, video clips were recorded at 5,339 fps, with a field of view of 3.40×3.3 mm. Subsequently, frame-by-frame processing of the recorded video clips was performed using specialized software provided by the high-speed camera manufacturer. The results are presented as a sequence of frames starting from the moment the ultrasound was activated. The time indicated in the upper right corner of each frame was calculated as the ratio of the frame number N (starting from the moment the ultrasound was activated) to the frame rate (t = N/5,339). Surface structure and roughness studies During all the above-mentioned types of treatment, the lateral surface of the samples was photographed using a METAM-RV-22 metallographic microscope. After ultrasonic SPD, a transverse microsection made from the sample was additionally examined to analyze changes in the microstructure resulting from the surface deformation. After reaching the treatment time beyond which no significant surface changes were observed, the roughness parameters were measured using a Model 130 profilometer to obtain surface profiles in the form of profilograms. The results were based on the average values from five measurements of the height roughness parameters Ra, Rz, Rmax. Changes in the sub-microgeometry of surfaces after treatment were evaluated by atomic forcemicroscopy (AFM) using a SMM-2000 scanning multimicroscope with an MSCT cantilever having a beam stiffness of 0.1 N/m. Microhardness was measured using the Vickers hardness test method on a PMT-3 device by indenting the surface with a diamond pyramid under a load of 50 g for 10 seconds. The results were based on the average values from five measurements taken in different locations of the sample. Fig. 4. Scheme of ultrasonic surface plastic deformation
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