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.

Thermal-sprayed WC–Co–Cr coatings are widely used to improve the wear and corrosion resistance of steel components operating under severe service conditions. This study investigates WC–Co–Cr coatings deposited by detonation spraying (DS), high-velocity oxy-fuel (HVOF), and atmospheric plasma spraying (APS) before and after ultrasonic nanocrystal surface modification (UNSM). The coatings were characterized using scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS), together with microhardness, tribological, abrasive, erosive, impact-abrasive, cavitation, corrosion, oxidation, and valve endurance tests. The results demonstrate that the deposition technology strongly affects the coating structure and performance. UNSM produced a pronounced increase in microhardness, reaching 1468 HV for DS + UNSM, 1596 HV for HVOF + UNSM, and 1561 HV for APS + UNSM. Ultrasonic treatment also reduced material loss under abrasive, erosive, impact-abrasive, and cavitation conditions. APS + UNSM demonstrated the best performance in the principal laboratory wear tests, with the lowest abrasive mass loss (0.42–0.45 mg), erosive mass loss (0.55–0.60 mg), impact-abrasive mass loss (0.75–0.85 mg), and cavitation mass-loss rate (0.33–0.38 mg/h). In tribological testing, APS + UNSM exhibited the lowest coefficient of friction (0.28), compared with 0.32 for HVOF + UNSM and 0.36 for DS + UNSM. In valve endurance testing, HVOF + UNSM showed the lowest plunger displacement growth rate (0.050 mm/h) and the longest calculated time to reach the 2 mm displacement criterion (22 h). Overall, the combination of thermal spraying and UNSM improves the mechanical and service performance of WC–Co–Cr coatings, while the optimal coating condition depends on the specific degradation mechanism and operating conditions.

The hardness and post-scratch surface morphology of Cr₃C₂–NiCr coatings subjected to ultrasonic nanocrystal surface modification (UNSM) were examined for detonation-sprayed (DS) and high-velocity oxy-fuel (HVOF) deposits. Four treated samples per deposition route were evaluated at static loads of 20 and 30 N and vibration amplitudes of 20 and 30 µm. Instrumental hardness was measured at a load of 300 mN with a dwell time of 10 s. The DS samples exhibited hardness values of 820–970 HV, whereas the HVOF samples covered the wider range of 546–1165 HV. The highest values were recorded for DS-T1 at 20 N/20 µm and HVOF-T4 at 30 N/30 µm. SEM fields acquired after scratch testing showed heterogeneous surface contrast and crack-like discontinuities in both coating series. These observations provide qualitative evidence of the post-test surface condition but do not isolate damage caused by UNSM or establish a ranking of scratch resistance. Available mean friction coefficients are reported as supplementary observations for six treated samples. The results demonstrate a sample-dependent hardness response and emphasize the need to assess local mechanical properties together with surface integrity.

This study investigates the effect of Ultrasonic Nanocrystal Surface Modification (UNSM) treatment on the microstructure, hardness, roughness, and tribological characteristics of 45 steel. The treatment was carried out under static loads of 20, 40, and 60 N. Microstructural analysis was performed using scanning electron microscopy. Mechanical properties were evaluated by instrumental indentation and Vickers hardness methods. It was established that UNSM treatment promotes the formation of a hardened surface layer and grain refinement due to severe plasticdeformation. The maximum instrumental hardness value, HIT, reached 5722.4 N/mm² at a load of 40 N. At the same time, a decrease in surface roughness and friction coefficient was observed. The obtained results demonstrate the high efficiency of UNSM treatment for improving the performance properties of 45 steel.

The effect of Ultrasonic Nanocrystal Surface Modification (UNSM) on the structural, mechanical, and tribological properties of WC–12Co coatings deposited by high-velocity oxygen fuel (HVOF) spraying onto 12 × 18H10T steel was investigated. The coatings were treated with UNSM using four combinations of amplitude (20 and 50 μm) and static load (10 and 40 N). Morphology and microstructure were evaluated using scanning electron microscopy; additionally, surface roughness, porosity, Vickers microhardness, Martens hardness, coefficient of friction, and acoustic response during scratching under a constant load were determined. The greatest relative reduction in Ra was observed for L2 (64.97%), while L4 exhibited the lowest final Ra value (1.512 ± 0.256 μm) and the greatest reduction in Rz (76.07%) and porosity (from 29.632% to 4.838%). The reduction in Ra and Rz was statistically significant for all treatment conditions. The maximum Martens hardness was observed for L3 (9162 N/mm²), whereas the differences in Vickers microhardness relative to the untreated coating were not statistically significant. The average coefficient of friction after UNSM did not decrease relative to the untreated coating, whereas samples L2–L4 exhibited lower maximum acoustic emission values during scratching. Overall, the results indicate a non-monotonic dependence of the coating properties on UNSM amplitude and static load. The findings indicate that the selection of the UNSM treatment mode should be based on the required balance between surface morphology, mechanical properties, and resistance to localized mechanical damage.