OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 Fig. 9. Micro-stress as a function of processing time for cast and additively manufactured ZhS6U alloy samples after low frequency impact processing 70 MPa to a value of 480 MPa. Thus, HF impact treatment induces the development of second-order stresses in both alloys compared to their initial states. The results of microstress evaluation show the similarity of dependences observed at both LF (Fig. 9) and HF impact treatment (Fig. 10). At the same time, it can be noted that the dependence of the microstress value at HF processing differs from LF by a smoother change of values. The average microhardness values of the initial cast and additively obtained ZhS6U are 430 and 470 HV, respectively (Fig. 11). The impact treatment of the surface of the ZhS6U alloy leads to an increase in the microhardness values. In general, at LF impact treatment of the nickel alloy surface for 20 seconds, the microhardness values reach 600 HV. When a cast sample is LF impacted for 40 seconds, the microhardness drops to 555 HV. The microhardness of additively manufactured ZhS6U at LF impact surface treatment reaches values of 650 HV at an impact time of 40 seconds due to the severe plastic deformation process that occurs after LF impact surface treatment. The increase in the number of deformation bands indicates a high dislocation density, which increases the microhardness (Fig. 3, f). Surface deformation treatment of cast and additively manufactured ZhS6U alloy at high frequencies leads to an increase in microhardness, which is related to the development of plastic deformation and changes in the microstructure of the surface layer (Fig. 4, a-e, Fig. 12). During HF impact treatment of the cast nickel alloy surface, the microhardness values of the samples increase to 580 HV with an impact time of 5 minutes. When the cast sample is subjected to HF impact treatment for 10 minutes, the microhardness decreases to 520 HV; however, with 20 minutes of HF impact treatment, it increases again – to 575 HV. At the same time, HF impact treatment of the surface of the additively manufactured ZhS6U alloy leads to an increase in the microhardness value of the material to 670 HV with an impact time of 10 minutes. HF impact treatment for 20 minutes leads to a decrease in microhardness, which is likely due to recrystallization. Fig. 10. Micro-stress as a function of processing time for cast and additively manufactured ZhS6U alloy samples after high frequency impact processing
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