OBRABOTKAMETALLOV Vol. 27 No. 1 2025 technology The histogram analysis showed that the processing parameters significantly affect the continuity of the white layer of processed chromium-containing steels 0.4 C-Cr and 0.35 C-Cr-Mn-Si. With CPEDM at the maximum mode, the continuity of the white layer is, on average, two times less than when processed at the minimum mode. It was found that the continuity of the white layer of 0.4 C-Cr steel is higher than that of 0.35 C-Cr-MnSi steel by 10 % with CPEDM at the maximum mode and by 17 % with CPEDM at the minimum mode. Photographs of the processed surface of 0.35 C-Cr-Mn-Si and 0.4 C-Cr steel samples are shown in Fig. 7. Visual assessment of the metallographic examination results showed that numerous microcracks form on the treated surface during the EDM process of 0.35 C-Cr-Mn-Si and 0.4 C-Cr steels. An assessment was made of the number of microcracks per unit area of the surface processed by electrical discharge machining. Table 6 presents the results of the quantitative assessment. Based on the obtained data on the number of microcracks, a histogram was constructed (Fig. 8). The histogram analysis showed that during CPEDM of chromium-containing steels 0.4 C-Cr and 0.35 C-Cr-Mn-Si, the number of microcracks formed varies significantly depending on the parameters of the processing mode. The number of microcracks formed during processing at the maximum parameter settings is more than two times greater than that during processing at the minimum parameter settings. It was established that the number of cracks in the white layer is comparable for 0.4 C-Cr and 0.35 C-Cr-Mn-Si steels, with the difference not exceeding 10 %. Ta b l e 5 Continuity of the white layer of the machined surface after copy-piercing EDM CPEDM mode Continuity of white layer, % 0.4 C-Cr 0.35 C-Cr-Mn-Si min 94.00 51.00 max 84.00 34.00 Fig. 6. Histogram of white layer continuity
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