The paper presents the results of electrolytic-plasma surface hardening (EPSH) of steel 40KhN. The optimal electrolyte composition for EPSH of 40KhN steel containing 10% sodium carbonate and 15% carbamide, which does not cause the surface layer to erosion, oxidation and decarburization, is determined. As a result of EPSH, a modified layer was obtained with increased hardness and wear resistance. We studied the changes in the microhardness of the surface layer of steel 40KhN after the EPSH, as well as the dependence of the microhardness on the duration of the effect of the electrolyte plasma. The paper presents tests for wear resistance of samples before and after electrolytic-plasma surface hardening. Tests have shown that the treated samples show a significant decrease in wear rate compared with the original sample. To clarify the structural factors affecting the wear resistance of steel, the structural-phase states of the hardened surface layers of steel 40KhN were investigated. X-ray structural analysis showed that in the initial state the α-phase and cementite (Fe3C) are present in the structure of 40KhN steel. After the EPSH, diffraction patterns showed a broadening of the interference lines from the crystallographic plane (110). The broadening of the interference line (110) is associated with an increase in the density of dislocations and the formation of martensite and is determined mainly by the tetragonal nature of martensite.Keywords: Electrolytic-plasma surface hardening (EPSH), steel, wear resistance, structure
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