Enhancement of Medium-Carbon Steel Corrosion and Wear Resistance by Plasma Electrolytic Nitriding and Polishing

Andrey Apelfeld,Anatoly Borisov,Igor Suminov,Ilya Dyakov,Ivan Tambovskiy,Sergey Silkin,Sergey Grigoriev,Sergei Kusmanov,Boris Krit

doi:10.3390/met11101599

Andrey Apelfeld, Anatoly Borisov + Show 7 more

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https://doi.org/10.3390/met11101599

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Abstract

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.

Highlights

Plasma nitriding is a widely used technological process in the surface engineering of metal machine parts
The results of X-ray diffraction analysis of the samples after plasma electrolytic nitriding (PEN) show the formation of FeO and Fe3 O4 phases as a result of high-temperature oxidation of steel in the vapor-gaseous envelope (VGE), iron nitrides Fe4 N as a result of diffusion of nitrogen, martensite and retained austenite as a result of quenching (Figures 1–3)
In contrast to the weight loss, the amount of iron in the solution after the plasma electrolytic polishing (PEP) without electrolyte circulation exceeds that when the electrolyte flows around the samples

Summary

Introduction

Plasma nitriding is a widely used technological process in the surface engineering of metal machine parts. In discharges with a hollow cathode [4,5] and arc discharges [6,7], nitriding is carried out in vacuum chambers with special screens and surface erosion by ion sputtering is blocked. For cleaning and etching the surface, along with ion beams, neutral fluxes of atoms and molecules are used [8,9]. These technologies in [4,5,6,7,8,9,10] are intermediate before the application of hard ceramic coatings to cutting tools. Plasma electrolytic technologies show an obvious tendency to expand in usage that is reflecting in the number of publications, and in the more systematic description of these methods

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