The development of thin, wear-resistant coatings is a relevant area in the field of surface engineering, especially given the increasing demand for resource efficiency and reliability of machine elements. In this study, we investigate the structural and phase composition, tribological characteristics, and physical and mechanical properties of zirconium carbonitride (ZrCN) coatings deposited by high-velocity oxygen-fuel spraying (HVOF) on U8G carbon steel substrates. Particular attention is paid to the influence of spraying parameters, in particular air pressure, on the formation of coatings and their performance properties. X-ray phase analysis methods revealed the formation of Zr₂CN, ZrC, ZrN, ZrO₂, and Fe₃O₄ phases, with the dominance of the cubic phase ZrN(C) with a lattice parameter of a = 4.6360 Å. Tribological tests have shown that at an air pressure of 0.38 MPa, the minimum friction coefficient is achieved, presumably due to the formation of an amorphous CN_x phase with a self-lubricating effect. The wear mechanism is predominantly abrasive in nature; the width of wear tracks is 329–759 μm. The coatings demonstrate a significant increase in microhardness—up to 1512–1857 HV, which is 4–4.5 times higher than the substrate. The results of adhesion tests carried out in accordance with ASTM D4541-22 showed a maximum adhesion strength of 14.56 MPa. The results obtained confirm the high efficiency of thin ZrCN coatings obtained by the HVOF method as a promising solution for protecting metal surfaces subject to intense wear in tribological systems.

This study investigates the effect of oxygen pressure during high-velocity oxy-fuel (HVOF) spraying on the formation and structural-phase characteristics of ZrCN coatings deposited on 65G steel. The coatings were produced using the Termika-3 system under fixed parameters of fuel, air flow, and spray distance, with oxygen pressure varied in the range of 4.0-4.5 bar. X-ray diffraction analysis revealed that the main coating matrix consists of a Zr(C,N) solid solution with a face-centered cubic lattice (Fm-3m). Increasing the O₂ pressure leads to partial thermal decomposition of ZrCN and the formation of ZrC, ZrN, and oxide phases such as t-ZrO ₂ . Oxygen enrichment of the coatings results in grain refinement and lattice parameter expansion. The microhardness of the coatings (a-c) reaches 1512-1857 HV, which corresponds to an approximately fivefold increase relative to the initial sample. Based on the obtained results, it was shown that regulating the oxygen pressure in the HVOF jet significantly affects the phase composition, morphology, and adhesion quality, providing an optimal combination of hardness, ductility, and thermal stability.

Tungsten borides are promising superhard materials, but their mechanochemical synthesis requires prolonged processing, leaving the early and intermediate stages of mechanical alloying (MA) and the role of boron content largely unexplored. This study investigated the effect of boron content and high-energy MA duration (2–10 h) on the morphology, particle size distribution, and structural and phase evolution of W–B powder mixtures, comparing a near-stoichiometric W90B10 composition with a boron-excess W80B20 composition. Scanning electron microscopy, laser diffraction, X-ray diffraction, and TEM-EDS were used for characterization. The average particle size of W90B10 initially increased to 3.48 μm after 6 h and then decreased to 1.28 μm after 10 h, whereas W80B20 exhibited non-monotonic behavior, stabilizing at approximately 4.3 μm. With increasing MA duration, bcc-tungsten reflections broadened and weakened, indicating a highly disordered nanocrystalline state. Reflections of hexagonal WB₂ (crystallite size 12.5 nm) appeared in W90B10 after 8 h, whereas no crystalline boride phases were detected in W80B20 up to 10 h. TEM–EDS and SAED analyses revealed local compositional inhomogeneity and provided additional crystallographic support for the formation of nanocrystalline WB₂. These results show that boron content determines the kinetics of boride phase formation and the morphology evolution pathway during MA, identifying W90B10 as the more favorable composition for rapid nanocrystalline WB₂ synthesis.

This study investigates the effect of oxygen pressure on the structural-phase state, microstructure, mechanical properties and tribological behavior of Zr(C,N)-based coatings deposited on U8G tool steel by high-velocity oxygen fuel (HVOF) spraying. The coatings were produced at oxygen pressures of 4.0 × 10 ⁵ , 4.3 × 10 ⁵ and 4.5 × 10 ⁵ Pa, while the spraying distance, propane pressure and air pressure were kept constant. Variation in oxygen pressure was found to affect the relative XRD peak intensities, Rietveld-refined phase fractions, diffraction-line broadening parameters, coating thickness, porosity and tribological response. However, since the coatings exhibited differences in thickness, the interpretation of XRD intensity variations was performed with consideration of possible thickness-related effects and substrate contribution. X-ray diffraction and Rietveld refinement indicated the formation of a multiphase Zr(C,N)-based system containing carbonitride, carbide, nitride, oxide and α-Fe phases. The coating deposited at 4.3 × 10 ⁵ Pa showed the most favorable combination of Zr(C,N)-type phase retention, reduced oxide fraction, low apparent cross-sectional porosity and relatively uniform microstructure. Williamson–Hall analysis suggested the largest coherent scattering domain size of approximately 82 nm and the lowest microstrain of approximately 0.30% for this condition, although these values should be considered as comparative estimates due to partial overlap of Zr ₂ CN, ZrC and ZrN reflections. SEM/EDS analysis showed that the coating obtained at 4.3 × 10 ⁵ Pa had the most homogeneous distribution of Zr, C and N and relatively low oxygen content. This coating also exhibited the highest microhardness (1826 ± 38.4 HV _0.5 ), the highest apparent pull-off adhesion strength (18.4 MPa) and the lowest friction coefficient (μ ≈ 0.54 ± 0.01). Quantitative wear assessment according to ASTM G99 showed that this coating had the lowest wear volume and specific wear rate among the investigated samples. SEM examination of wear tracks suggested a correlation between oxygen pressure, coating morphology and wear-track features; however, direct post-wear chemical analysis of the tribofilm would be required to confirm the detailed wear mechanisms. Overall, the results indicate that an oxygen pressure of 4.3 × 10 ⁵ Pa provides the most balanced coating characteristics under the investigated HVOF conditions.

This study examines the effect of spark plasma sintering (SPS) temperature on the phase composition, microstructure, densification, and microhardness of cobalt-free WC–Fe and WC–Fe–Ni hard alloys. Increasing the sintering temperature from 1250 °C to 1300 °C improved densification in both alloy systems. Residual porosity decreased from 13.2% to 12.7% in the WC–Fe–Ni alloy and from 13.8% to 12.0% in the WC–Fe alloy, while the density increased from 12.39 g/cm³ to 12.46 g/cm³ and from 12.15 g/cm³ to 12.40 g/cm³, respectively. The WC–Fe -Ni alloy exhibited a more homogeneous microstructure and higher microhardness, increasing from 708 $\pm$ 10 HV_0.2 to 823 ± 15 HV_0.2, whereas the WC–Fe alloy showed an increase from 630 ± 15 HV_0.2 to 770 ± 5 HV_0.2. X-ray diffraction analyses identified Fe₃W₃C, FeNi₃, and (Fe, Ni) solid-solution phases formed during SPS. The results indicate that both the sintering temperature and binder composition influence densification, phase evolution, and mechanical performance. Among the investigated materials, the WC–Fe–Ni alloy showed better microstructural stability and hardness than the WC–Fe alloy. These findings suggest that Fe–Ni binders are promising candidates for cobalt-free cemented carbides, although additional studies on fracture toughness and wear resistance are required before practical cutting-tool applications can be fully assessed.