OBRABOTKAMETALLOV Vol. 27 No. 1 2025 technology Table 3 presents theoretical values of the thickness of the white layer formed during CPEDM, obtained on the basis the analysis of Fig. 3. Table 3 presents theoretical values of the thickness of the white layer formed in the CPEDM process, obtained on the basis of the analysis of Fig. 3. Fig. 4 shows images obtained from metallographic examination of microsections of 0.35 C-Cr-Mn-Si and 0.4 C-Cr steel samples after copy-piercing EDM at maximum and minimum modes. Ta b l e 3 Theoretical values of white layer thickness CPEDM mode Average value of white layer thickness, µm 0.4 C-Cr 0.35 C-Cr-Mn-Si min 25 20 max 80 60 a b с d Fig. 4. Microstructure of the surface layer of samples after copy-piercing EDM at 200× magnification: a – 0.4 C-Cr, min; b – 0.4 C-Cr, max; c – 0.35 C-Cr-Mn-Si, min; d – 0.35 C-Cr-Mn-Si, max
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