Electrolytic-Plasma Nitriding of Austenitic Stainless Steels After Mechanical Surface Treatment
Rakhadilov B. Satbayeva Z. Maulit A. Kadyrbolat N. Rustemov A.
November 2025Multidisciplinary Digital Publishing Institute (MDPI)
Crystals
2025#15Issue 11
In this work, the effect of preliminary mechanical surface treatment on the kinetics of formation, phase composition, and functional properties of the nitrided layer during electrolytic-plasma nitriding (EPN) of austenitic stainless steel 12Kh18N10T (AISI 321) was investigated. In contrast to traditional approaches, for the first time, this work establishes a direct correlation between the degree of surface deformation induced by shot peening and the formation of the expanded austenite (γN) phase under low-temperature plasma conditions. Quantitative X-ray phase analysis revealed a lattice parameter expansion of Δa/a0 ≈ 1.4–1.8% and a gradual transformation of γ-Fe → γN without the formation of CrN nitrides at moderate intensity of preliminary treatment. According to SEM/EDS data and microhardness profiles, a multilayer structure was formed, consisting of a thin surface film of CrN/Fe4N, a developed γN zone with a thickness of 12–15 µm, and a stable austenitic γ-Fe matrix. The surface microhardness increases to 880 ± 20 HV, while the friction coefficient decreases to 0.35–0.40, corresponding to a wear reduction of approximately 55% compared to the initial steel. The results provide a mechanistic understanding of nitrogen diffusion through defect-enriched subsurface layers and show that optimal preliminary deformation (d = 6 mm, v = 40 Hz, t = 20 min) promotes controlled formation of the γN phase with minimal lattice instability. The proposed combined approach—shot peening + EPN—is an effective method for producing wear- and corrosion-resistant surfaces of austenitic steels under atmospheric plasma conditions.
electric discharge , electrolytic-plasma nitriding , electron density , emission spectroscopy , expanded austenite γN (S-phase) , shot peening , surface modification
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PlasmaScience” LLP, Ust-Kamenogorsk, 070018, Kazakhstan
Research School of Physical and Chemical Sciences, Shakarim University, Semey, 071412, Kazakhstan
Engineering Center “Strengthening Technologies and Coatings”, Shakarim University, Semey, 071412, Kazakhstan
PlasmaScience” LLP
Research School of Physical and Chemical Sciences
Engineering Center “Strengthening Technologies and Coatings”
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