OBRABOTKAMETALLOV technology Vol. 27 No. 1 2025 Ta b l e 4 Experimental 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 23.86 20.79 max 83.00 58.00 Fig. 5. Histogram of white layer thickness values Visual assessment of the micrographs indicates that a characteristic white layer forms on the processed surface of 0.4 C-Cr and 0.35 C-Cr-Mn-Si steels during CPEDM. The thickness of this layer varies significantly depending on the processing modes (Table 4). To compare theoretical and experimental values of the white layer thickness, a histogramwas constructed (Fig. 5). Based on the analysis of Fig. 5, the experimental values of the white layer thickness range from 20 to 25 μm for CPEDM with the minimum mode and from 55 to 85 μm with the maximum mode. It has been established that with CPEDM under identical conditions, the white layer thickness of lowalloy 0.4 C-Cr steel is greater than that of medium-alloy 0.35 C-Cr-Mn-Si steel. This can be attributed to the higher thermal conductivity and lower melting point of 0.4 C-Cr steel. A correlation between theoretical and experimental values is observed. The deviation of the theoretical values of the white layer thickness from the experimental values is no more than 5 %, confirming the validity of the obtained models. The results demonstrate that the developed theoretical models of pit formation during CPEDM allow, with the stated accuracy, prediction of the white layer thickness depending on the processing parameters and physical and mechanical properties of the workpiece material. Based on the analysis of Fig. 4, the white layer formed during CPEDM of 0.4 C-Cr and 0.35 C-Cr-MnSi steels is distributed unevenly, with numerous voids and cavities observed. To assess the continuity of the white layer, a quantitative assessment of the total area of the white layer on microsections and voids was performed (Table 5). Based on the obtained data, a histogram was constructed (Fig. 6).
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