The influence of technological parameters of plasma electrolytic nitriding and polishing on the wear resistance and corrosion resistance of medium-carbon steel is considered. The morphology and roughness of the surface, phase composition and microhardness of the modified layer have been investigated. Wear resistance was studied under dry friction conditions with bearing steel as counter-body. It was found that plasma electrolytic polishing removes the loose part of the oxide layer and provides a two-fold decrease in surface roughness compared with untreated steel, and 2.8 times compared with the nitrided one. Combined processing at optimal technological parameters leads to an increase in microhardness up to 1130 HV, an increase in wear resistance by 70 times, and a decrease in the corrosion current density by almost 3 times in comparison with untreated steel.

The possibility of using an aqueous non-toxic electrolyte of ammonium nitrate and glycerin for the cathodic plasma electrolytic nitrocarburizing of low-carbon steel is considered in this paper. Surface morphology and roughness, element and phase compositions, and microhardness of the modified layer were investigated. Kinetic calculations of the processes of nitrogen and carbon diffusion into the steel surface are proposed, taking into account their mutual influence. Wear resistance was studied under dry friction conditions with tool alloy steel as a counter-body. Corrosion studies are performed using potentiodynamic polarization curves in 3.5% sodium chloride solution. The plasma electrolytic nitrocarburizing in an aqueous electrolyte with ammonium nitrate and glycerin is established to increase surface hardness up to 980 HV due to the formation of a nitrocarburized layer with 1.35 ± 0.12% carbon and 0.32 ± 0.08% nitrogen concentration. The influence of erosion in electrolyte plasma and high-temperature oxidation on the morphology and surface roughness is shown. The presence of a dense oxide layer, low surface roughness, and high hardness of the diffusion layer favor a decrease in the friction coefficient by 1.3 times, weight wear by 1.8 times and corrosion current density by 1.4 times.