OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 During impact treatment, a pre-stress of 65 N was applied for all methods, which is attributed to the dynamic loading process. In the case of low-frequency impact treatment, this pre-stress ensures stable contact between the treatment tool and the surface of the material being treated. In the case of small oscillation amplitudes, this pre-stress facilitates energy dissipation in the contact zone between the impact treatment tool and the sample surface, as well as the absorption of impact energy by the sample surface to induce surface deformation. The structure and roughness of the samples’ surface after impact treatment were investigated by optical microscopy using an Olympus LEXT OLS4100 confocal laser scanning microscope. The optical microscopy method was also used to study the structure of the processed alloys in cross section. For this purpose, each sample after mechanical impulse treatment was prepared in the normal to the surface of treatment cross section by the standard technique for metallographic studies, including sanding on abrasive paper (SiC) with grit up to P2,000, followed by finishing polishing on 1/0 polishing slurry. Values of microhardness of the treated surface without preliminary preparation were measured on a Duramin-5 microhardness tester. The phase composition of the treated surfaces of the samples without preliminary preparation was determined using an X-ray diffractometer DRON-8 with CuKα-radiation. The microstresses were analyzed by evaluating the full width at half maximum (FWHM) of the X-ray reflex (220). Due to the absence of a reference (unstressed) sample, the FWHM value of the original sample at symmetric geometry of imaging was taken as a starting point. The real FWHM (β) was calculated using Equation 1: 2 2 B b β = − , (1) where B is FWHM reflex (220) after deformation processing; b is FWHM of initial sample’s reflex (220). Equation 2 defined the lattice microstrain (ε) for each strain value after deformation processing: 4 tan β ε = ⋅ Θ, (2) where Θ is angular position of the analyzed reflex (220). Tribological tests of treated surfaces without preliminary preparation were carried out by the scratchtesting method on a Revetest-RST macro-scratch tester with a diamond indenter at a constant load of 10 N for 3 mm (radius of curvature is 200 μm). Results and discussion Fig. 1 shows optical micrographs of the surfaces of LF-treated ZhS6U alloy samples. The surface roughness of the cast alloy after LF impact treatment ranges from 2 to 5 μm (Fig. 1, a-c), which is similar to the surface roughness of the additively manufactured alloy (Fig. 1, d-f). Optical images of the surface of cast and additive alloy samples subjected to HF impact treatment are presented in Fig. 2. The formation of an additional layer was observed on the surface of all HF-treated nickel alloy samples, the morphology of which varies depending on the impact time. The surface roughness of the cast samples after HF treatment is about 2 μm (Fig. 2, a-c). The microstructures of cast (Fig. 3, a, c, e) and additive obtained (Fig. 3, b, d, f) ZhS6U alloy in cross section after LF mechanical pulse treatment are presented in Figure 3. The analysis of metallographic images showed that the extent of plastic deformation increases with both increasing of processing time and depending on the initial condition of the material. Fig. 3, b, d, f shows that LF mechanical pulse treatment of the additively manufactured ZhS6U alloy results in the formation of a plastically deformed surface layer, characterized by slip bands of varying orientations, as indicated by black lines and red arrows. The alloy structure changes to a depth of ~90 μm with an increase in the processing time up to 40 seconds (Fig. 3, f). The cross-sectional microstructure of the cast (Fig. 4, a, c, e) and additively manufactured (Fig. 4, b, d, f) ZhS6U alloy after HF mechanical pulse treatment exhibits differences primarily related to the initial material condition. However, optical microscopy of the cross-sections reveals that the additively manufactured
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