The paper presents a comparative analysis of technologies for forming metal-ceramic coatings of WC-NiCr, Cr₃C₂-NiCr, and Al₂O₃-NiCr systems obtained by high-velocity oxygen fuel (HVOF) and detonation spraying methods. The aim of the study was to determine the influence of the coating technology on the microstructure, physical-mechanical and tribological properties of the coatings. The study included analysis of the morphology of the starting powders and the microstructure of the coatings using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Microhardness was determined using the FISCHERSCOPE HM 2000 system, and tribological characteristics were studied using the ball-on-disc method on an Anton Paar TRB³ tribometer in accordance with ASTM G133-95 and ASTM G99 standards. It was found that the spraying method has a significant effect on the structure and performance characteristics of coatings. For carbide systems (Cr₃C₂-NiCr and WC-NiCr), the HVOF method is more effective, providing the formation of a dense, fine-grained structure, increased hardness, and a reduced friction coefficient. For the Al₂O₃-NiCr oxide system, detonation spraying proved to be preferable, providing higher hardness and stable tribological characteristics. The results obtained allow for a reasonable choice of coating formation technology depending on their composition and operating conditions.

This study investigates the effects of applied voltage and treatment duration during electrolytic-plasma hardening (EPH) on the microstructure, phase composition, hardness, surface condition, and tribological behavior of 20X steel. EPH was performed in a 12 wt.% Na₂CO₃ aqueous electrolyte at voltages of 280, 300, and 320 V for 4 and 6 s. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, instrumented indentation, surface profilometry, and ball-on-disk tribological testing were used to characterize the treated specimens. The 280 V/4 s, 300 V/4 s, 320 V/4 s, and 280 V/6 s conditions produced thermally modified surface layers without visible surface damage, whereas treatment at 300 and 320 V for 6 s resulted in localized surface melting. Among the undamaged specimens, the highest hardness was obtained at 280 V, reaching 329.6 ± 15.8 HV after 4 s and 332.1 ± 26.3 HV after 6 s, corresponding to an approximately 1.83–1.85-fold increase relative to the initial value of 180 HV. XRD revealed a predominantly α-Fe-based matrix, while weak secondary reflections could not be assigned reliably to specific phases. The minimum steady-state coefficient of friction was obtained at 300 V/4 s (0.444 ± 0.054), whereas the narrowest wear track was observed at 320 V/4 s (379.48 ± 36.24 μm). No direct correlation was found between hardness and tribological response, indicating that surface roughness and microstructural state should also be considered when selecting treatment parameters. The results define a stable EPH processing window for 20X steel and demonstrate that parameter selection should be based on a combined assessment of surface integrity, hardness, and tribological performance.