OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 nickel alloy. Analysis showed that both treatment methods significantly modify the surface and bulk of the material; however, the nature of the changes depends on both the frequency of the impact and the initial state of the alloy. During LF treatment of the cast alloy, an increase in the volume fraction of the strengthening γ’ phase (Ni3Al(Ti)) is observed, correlating with an increase in microstrains up to 220 MPa and microstrains up to 0.1 %. For the additively manufactured alloy, a similar treatment induces more pronounced changes: microstresses reach 600 MPa, and strains reach 0.3 %, which is probably related to the initial inhomogeneity of the structure characteristic, typical for additive technologies. HF treatment, in contrast, leads to the formation of an additional surface layer containing the TiO2 phase, which is absent after LF treatment. This suggests thermo-activation processes, such as oxidation, that are activated by high-frequency impact. The mechanical properties of the alloys exhibit a dependence on the treatment method and initial structure. The microhardness of both materials increases after impact treatment; however, the additively manufactured alloy retains its advantage: after LF impact treatment, its hardness reaches 650 HV, compared to 555 HV for the cast counterpart, while after HF impact treatment, it reaches 670 HV compared to 580 HV. Interestingly, a decrease in hardness is observed with prolonged treatment (40 seconds of LF treatment or 20 minutes of HF treatment), which may be explained by stress relaxation or partial recrystallization. The additivelymanufactured alloy also exhibits increased sensitivity to stress accumulation: after LF impact treatment, its microstresses are 2–3 times higher than those of the cast material, due to defects typical of additively manufactured production. HF impact treatment, in turn, causes a smoother increase in stresses, likely due to the lower intensity of plastic deformation at high frequencies. The tribological properties of the alloys, assessed using scratch testing, demonstrate mixed trends. For the cast alloy, LF treatment reduces the coefficient of friction only at the maximum treatment time (40 seconds), whereas the additively manufactured alloy shows a progressive reduction in friction from 0.19 to 0.075, which may be associated with surface hardening and a reduction in adhesion. HF treatment leads to opposite effects: friction decreases in the cast alloy with longer treatment, while temporarily increasing in the additively manufactured alloy, correlating with the formation and instability of the TiO2 oxide layer. The scatter in the coefficient of friction values, particularly noticeable under a constant load of 20 N, is explained by the surface roughness after impact treatment. Comparing LF and HF treatments highlights their key features. LF treatment provides intensive strengthening but is accompanied by a significant increase in stresses, particularly critical for the additively manufactured alloy. HF treatment, in contrast, promotes the formation of multiphase surface layers involving oxide phases, which potentially improves wear resistance; however, it requires careful selection of treatment time to minimize softening. These differences necessitate an individualized approach to selecting treatment parameters depending on the alloy manufacturing method. In conclusion, this study confirms that the additively manufactured ZhS6U alloy, despite its initially high hardness, requires caution during long LF treatment due to its tendency to accumulate stresses. HF treatment, in turn, opens up opportunities for controlling the structure of the surface layer, but its effectiveness depends on the stability of the phases formed. For practical application of the results, further research is important, focusing on evaluating the cyclic stability of modified structures and their corrosion resistance under operating conditions. Conclusion The structural-phase state of the treated surfaces after low-frequency (LF) and high-frequency (HF) impact treatment is similar for both alloys. The main phases in both materials, as in the initial state, are Ni(γ) and Ni3Al(Ti) (γ’). However, LF impact treatment of the cast ZhS6U alloy leads to an increase in the volume fraction of the γ’ phase, while HF impact treatment results in the formation of TiO2 in the alloy. In addition, high-frequency impact treatment of both alloys leads to the formation of an additional layer on the treated surface, the morphology of which depends on the treatment time. Electron beam additive manufacturing (EBAM) alloy samples exhibited higher values of lattice microstrains, microstresses, and surface microhardness compared to the cast alloy samples, regardless of
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