Rezumat
CZU 544.558+66.088
DOI https://doi.org/10.52577/eom.2021.57.5.27
The structural-phase composition and some properties of medium-carbon steel modified surface after cathodic plasma electrolytic nitriding in a solution of ammonium chloride and ammonia have been studied. It is shown that cathodic nitriding of a steel surface is accompanied by high-temperature oxidation with the formation of oxides FeO, Fe2O3, and Fe3O4, as well as nitrogen diffusion and quenching with the formation of FeN, Fe3N, and Fe4N phases, martensite and the retained austenite. The competing effect of surface erosion by the actions of discharges and high-temperature oxidation on the morphology and roughness of the surface was revealed. It was established that the maximum microhardness of the modified layer reaches 1040 HV, and the corrosion current density of the nitrided surface decreases by a factor of 1.5–2.4.
Keywords: cathodic plasma electrolytic treatment, nitriding, microstructure, surface roughness, microhardness, corrosion resistance.