OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 conventional production methods, additive technologies can eliminate these disadvantages, providing high accuracy and speed in nickel alloy production, and minimize the formation of defects [4, 5] and allow the components to be repaired [6]. The main problem with nickel alloys produced by various methods is the formation of cracks that spread deep into the material over time, contributing to fatigue failure and a reduced product lifespan [7–10]. To minimize fatigue failure of nickel alloys, various methods of surface modification are used, such as laser shock treatment [11, 12], sand blasting [13], shot blasting [14] and electric discharge machining [15, 16]. In [17], the authors investigated the effect of laser shock treatment on the mechanical properties and microstructure of nickel alloy K403. Fatigue tests revealed that the formed nanocrystalline layer significantly increases the fatigue life of the alloy under high-frequency cyclic loading, resulting in a 2.44-fold increase in the samples’ lifespan compared to the initial state. In [18], the authors investigated the effect of ultrasonic nanocrystalline surface modification on the reduction of hydrogen embrittlement of Inconel-625 nickel alloy fabricated by additive manufacturing. Tensile tests showed that after hydrogen saturation, the samples showed an increase in the percentage of elongation of about 6.3 % after surface modification. Grain refinement, as well as formation of residual compression stresses and an increase in dislocation density, which also prevents hydrogen penetration into the material, cause an improvement of mechanical properties. The issue of surface modification of nickel alloy by mechanical pulse impact treatment remains poorly studied. At the same time, this method is widely used in industry as an effective way to improve the properties of metallic materials by forming a hardened surface layer, reducing embrittlement, and reducing the residual stress level [19, 20]. The purpose of this work was to compare the influence of mechanical pulse impact treatment on the change in structural-phase state and surface properties of ZhS6U nickel alloy obtained by electron-beam additive manufacturing and casting. To achieve the purpose, it was necessary to solve the following tasks: – to determine the effect of mechanical pulse impact treatment on the structural-phase state of the surface of ZhS6U nickel alloy produced by casting and by the electron-beam additive manufacturing method (EBAM); – to determine the influence of mechanical impulse impact treatment on microhardness and tribological properties of the surface of ZhS6U nickel alloy obtained by casting and electron-beamadditivemanufacturing. Materials and methods In this work, the ZhS6U nickel alloy (analog of K465) was studied (composition is given in Table), which was produced by casting and electron-beam additive manufacturing (EBAM) methods. Mechanical pulse impact treatment of the surface of the ZhS6U alloy was performed with a tool made of VT20 titanium alloy, with the area of contact with the surface of the sample being 5×5 mm. Composition of ZhS6U alloy Fe C Ni Cr Mo W Co Nb Ti Al Others ≤1 0.13–0.2 Balance 8.0–9.5 1.2–2.4 9.5–11.0 9.0–10.5 0.8–1.2 2.0–2.9 5.1–6.0 ≤0.93 Two impact treatment methods were used to process the ZhS6U alloy surface. The first method involved treating the surface of the ZhS6U alloy samples with a low-frequency (LF) fundamental harmonic of 46.6 Hz and an oscillation amplitude of 498 μm. The exposure times for the samples were 10, 20, and 40 s. The second method involved treating the surface of the alloy samples with a high-frequency (HF) impact frequency of 21.8 kHz and an oscillation amplitude of 6 nm. The exposure times for these samples were 5, 10, and 20 min. Before impact treatment, the surface of the samples was prepared by means of abrasive paper, from rough to fine, as well as 1/0 polishing slurry. The roughness of the obtained initial samples was 0.5±0.1 μm.
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