OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 6 No. 3 2024 tween the melt bath and the solidified metal. On samples No.1–3 (Fig. 2a–c) there are chaotically arranged pores with a diameter of 40–65 μm. The surface of sample No.4 is characterized by the smallest number of structural defects (pores with a diameter of 20–28 μm, cracks up to 2–3 μm wide). When examining these samples for the presence of defects (pores, microcracks), it was found that the most suitable sample for EDM is No.4 (Fig. 2d). Copy-piercing electrical discharge machining was carried out on an Electronica Smart CNC machine (Fig. 3b) in a transformer oil environment. The workpiece to be processed was made of stainless steel 0.12C-18Сr-10Ni-Тi. The values and range of input parameters are presented in Table 2. A Mahr Perthometer S2 profilometer (Fig. 3c) was used to evaluate the surface quality parameter Ra. The evaluation was carried out according to the GOST 2789-73 methodology. The surface topography of the samples and the number of defects on its surface were assessed using an inverted metallographic microscope of the NIM900 research class (Fig. 3d) at magnifications of ×300 and ×500. In order to determine the dependencies of the formation of the roughness parameter Ra of TE, as well as the wear of the working surface of TE, made of MS1 maraging steel, obtained using selective laser melting Fig. 2. Surfaces of sample: а – No.1; b – No.2; c – No.3; d – No.4 а b c d Ta b l e 2 Modes of copy-piercing EDM machining Mode Current I, A Pulse activation time Тon, μs Voltage U, V Minimum level 4 50 50 Medium level 6 75 75 Maximum level 8 100 100
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