OBRABOTKAMETALLOV technology Vol. 27 No. 1 2025 a b c d e Fig. 8. Microstructures of samples obtained at different working tool inclination angles: a – at α = 90°; b – at α = 75°; c – at α = 60°; d – at α = 45; e – without SPD The formation of a regular microrelief is clearly visible in the profilograms when processing with tool inclination angles of 90° and 75°. At smaller angles, the regularity is disrupted, but a greater change in roughness parameters occurs. Structure, hardness and microhardness When a significant clamping force is applied, the deforming element and emitter oscillate in common mode, i.e., the tool does not detach from the workpiece surface, and the processing conditions are close to smoothing. The main mechanism creating deformation of the surface layer is loading the workpiece surface with a ball under the action of a static clamping force and a significantly larger dynamic force created by the emitter vibrations. This results in both hardening and smoothing of the surface. Obviously, when the tool inclination angle is α = 90°, the force acting on the surface has only one normal component, FN, which creates the most favorable conditions for surface hardening (work hardening). As the angle decreases, the normal component FN decreases, and the tangential component Fτ increases. This leads to a decrease in hardness and a reduction in the depth of the hardened layer, but it also reduces the size of micro-irregularities due to smoothing. The results of metallographic studies are presented in Fig. 8. As the experimental results show (Fig. 9), the depth of the work-hardened layer increases with an increase in the inclination angle α of the working tool. At α = 45°, changes in the structure and properties extend to a depth of up to 50 μm, and at α = 90°, the depth reaches 345 μm. Obviously, the depth of the deformed layer is determined by the magnitude of the normal component FN of the force. At the same time, the highest microhardness at a depth of up to 50 μm is achieved at α = 45°, which is related to the shear strains created by the tangential component Fτ. Friction torque and wear Comparative wear tests of the specimens were carried out at a constant clamping force between the specimen and the counterbody N = 25 N. The spindle speed was n = 160 rpm. As a result, the dependence of the change in friction torque Mfr over 1,000 cycles was obtained (Fig. 10).
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