THE EFFECT OF THE ELECTROLYTE COMPOSITION ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF STEEL 45 AFTER CATHODIC ELECTROLYTE-PLASMA NITRIDING

In the present work, a study was conducted on the spectral characteristics of the electric discharge during the electrolytic plasma nitriding process, as well as the structural and phase changes occurring in austenitic stainless steel. The treatment was carried out in an electrolyte containing 10% soda ash (Na₂CO₃), 20% carbamide (CO(NH₂)₂), and 3% ammonium chloride (NH₄Cl) at a temperature of 550 °C for 10 minutes. Emis-sion spectroscopy revealed the presence of active nitrogen species (N₂⁺, N I), hydrogen (Hα), and oxygen (O I) in the plasma composition. The calculation of electron density based on the broadening of the Hα line from the Balmer series yielded a value of ap-proximately 8.5 × 10¹⁸ cm⁻³. X-ray phase analysis revealed the formation of nitride phases CrN and Fe₃N, as well as a solid solution of nitrogen in γ-Fe. Microstructural investigations using SEM revealed a three-layer structure of the nitrided layer: a ni-tride zone, a transition region, and the original austenitic matrix. Energy-dispersive X-ray analysis confirmed the presence of a nitrogen concentration gradient with depth.

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