Electrolytic Plasma Nitriding of Medium-Carbon Steel 45 for Performance Enhancement

This article analyzes the effect of electrolytic plasma nitriding on the performance of medium-carbon steel 45 under increased mechanical loads and in aggressive environments. Nitrided samples in carbamide electrolytes, both with and without the addition of ammonium nitrate, were compared to the initial material. SEM with EDX and XRD analysis was used to examine the microstructure and phase composition of nitrided samples. Wear resistance was studied using the ‘ball-on-disk’ method and Vickers microhardness testing, while corrosion resistance was studied using potentiodynamic polarization curves. The study results show that the sample without ammonium nitrate demonstrated better mechanical and corrosion properties due to a more homogeneous and denser nitride layer, approximately 10 µm thick, containing phases FeN and Fe4N. Its wear resistance doubled compared to that of the initial sample. The sample treated in an electrolyte with the addition of ammonium nitrate demonstrated a higher current density (2.8672 × 10−5 A/cm2) and a lower corrosion potential (−0.565 V) compared to the initial sample (i_corr = 1.8971 × 10⁻5 A/cm2, E_corr = −0.480 V) and the sample without ammonium nitrate (i_corr = 1.7315 × 10−5 A/cm2, E_corr = −0.376 V). This is due to the formation of an uneven nitride layer and the presence of microcracks on the surface.