The Effect of Electrolytic-Plasma Hardening Time on the Microstructure, Hardness, and Corrosion Behavior of Medium-Carbon Steel

Mukhametov Y. Shynarbek A. Rakhadilov B. Zhassulan A. Ibragimov N. Ormanbekov K. Kadyrbolat N.
December 2025 Multidisciplinary Digital Publishing Institute (MDPI)

Crystals
2025 #15 Issue 12

This study investigates the effect of electrolytic-plasma hardening time on the microstructure formation, hardness distribution, and corrosion behavior of grade 45 structural steel. The treatment was performed in a 15% aqueous sodium carbonate (Na₂CO₃) solution at an applied voltage of 300 V for different holding times (8, 10, and 12 s). Scanning electron microscopy and X-ray diffraction analyses revealed that increasing the EPH duration promotes the formation of a more uniform martensitic layer and reduces the amount of residual cementite. Microhardness measurements showed an increase in surface hardness from 190 HV for the untreated steel to 770 HV after the longest treatment. The cross-sectional hardness profile indicated the presence of a thin decarburized sublayer and a zone of maximum hardness corresponding to the martensitic structure. Potentiodynamic polarization tests in a 0.5 M NaCl solution showed a slight increase in corrosion current density after treatment; however, the corrosion rate remained within the range of 0.19–0.45 mm year⁻¹, confirming the satisfactory corrosion resistance of the hardened layer. The results demonstrate that controlling the EPH duration allows for optimizing the balance between enhanced hardness and maintained corrosion resistance of grade 45 steel.

corrosion resistance , decarburization , electrolytic-plasma hardening , grade 45 steel , martensite , microhardness , microstructure

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Engineering Center «Strengthening Technologies and Coatings», Shakarim University, Semey, 071412, Kazakhstan
Department of Physics and Informatics, Shakarim University, Semey, 071412, Kazakhstan
Plasma Science LLP, Ust-Kamenogorsk, 070000, Kazakhstan
Department of Bioengineering Systems, Shakarim University, Semey, 071412, Kazakhstan

Engineering Center «Strengthening Technologies and Coatings»
Department of Physics and Informatics
Plasma Science LLP
Department of Bioengineering Systems

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