OBRABOTKAMETALLOV technology Vol. 27 No. 1 2025 challenges in machining by cutting include hardening and the low thermal conductivity of the material being machined. During the cutting process, a significant amount of heat is generated, intensifying and localizing thermal effects on the cutting edge and accelerating tool wear [4‑5]. Wire-cut electrical discharge machining (WEDM) is an alternative method for manufacturing newgeneration, heat-resistant alloys [6‑10]. WEDM relies on removing material from the workpiece surface through heat generated by electrical impulses between the tool-electrode (TE) and the workpiece-electrode (WE). This process is independent of the material’s mechanical strength, hardness, toughness, and brittleness. There is no mechanical impact on the surface being processed [11‑14]. When implementing WEDM in production, it is essential to investigate surface quality assurance during machining. In WEDM, short-time unit pulses create intense, localized thermal and chemical effects on the workpiece surface. This forms an outer surface layer with physical and mechanical properties that differ from those of the base material. This layer may exhibit hardness values that differ from the base material and may contain cracks and other surface defects. The energy of each pulse and its duration determine the thickness of the modified layer. In addition to surface defects, residual stresses are also intensified in this layer. The intense thermal influence can cause residual stresses to appear in the surface layer of the workpiece. The magnitude and direction of these stresses depend directly on the processing modes, the material’s physical and chemical properties, and the surface layer characteristics [15‑18]. Tominimize the thickness of the modified surface layer, it is necessary to study the influence of machining modes on the formation of this layer [19‑21]. Machining modes affect the surface quality indicator, Ra (roughness). After WEDM, inhomogeneities can be observed in the surface relief, which is formed by the superposition of numerous craters. These craters result from the impact of unit pulses on the workpiece surface. The surface microrelief after WEDM differs from surfaces obtained by blade tool. The actual purpose is to provide surface quality at machining of heat-resistant nickel alloys of new generation by wire-cut electrical discharge machining. The purpose of this work is an experimental investigation with qualitative and quantitative analysis of the analysis of defects on the surface of samples made of a heat-resistant nickel alloy VV751P after WEDM. Objectives: – to analyze the thickness of the defective layer (white layer) on samples of the heat-resistant alloy VV751P manufactured in this study. – to analyze the surface quality indicator, Ra (µm), of the manufactured samples. – to conduct surface investigations for microcracks and structural defects using a laser scanning microscope and evaluate the temperature effect on the formation of the surface microrelief. – to conduct cyclic fatigue tests on specimens made of the heat-resistant alloy VV751P after WEDM. Research methodology The experiments were conducted at the Center of Additive Technologies of the ITM Department of the Perm National Research Polytechnic University. During the experiments the samples shown in Fig. 1 were produced. Wire-cut electrical discharge machining (WEDM) was performed using an Electronica EcoCut machine manufactured by ElectronicaMachineTools (Pune, India). Throughout the study, BercoCut wire manufactured by Berkenhoff GmbH (Herborn, Germany) with a diameter of 0.25 mm was used as the toolelectrode. Distilled water served as the working medium to facilitate the machining process The samples were machined using minimum and maximum modes. Each experiment was repeated three times to exclude the appearance of random errors. The pulse on-time (Ton, μs), pulse off-time (Toff, μs), and sample height were selected as the variable machining parameters. The modes of WEDM are presented in Table 1. The surface roughness of the machined samples after WEDM, in terms of the Ra parameter, was measured using a Perthometer S2 profilometer (Mahr GmbH, Göttingen, Germany) with a base trace length of 0.8 mm.
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