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•Hard Mo-Si-B and Mo-Al-Si-B coatings with h-MoSi2 phase as a main component.•Mo-Si-B possess higher hardness, improved oxidation resistance and better thermal stability.•Coatings ...withstand short-term oxidation at 1600 (Mo-Al-Si-B) and 1700°C (Mo-Si-B).•Oxidation is accompanied by phase transformations with formation of MoB and Mo5Si3 phases.
Mo-Si-B and Mo-Al-Si-B coatings were deposited by DC magnetron sputtering of MoSiB and MoAlSiB composite targets fabricated by the self-propagating high-temperature synthesis method. The structure, element and phase composition of coatings were studied by means of scanning and transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive spectroscopy, and glow discharge optical emission spectroscopy. To evaluate their oxidation resistance, the coatings were annealed in air in the temperature range of 1200–1700°C during different time slots between 10min and 5h. The obtained results demonstrated that the Mo-Si-B coatings possess higher hardness, improved oxidation resistance and better thermal stability compared with their Mo-Al-Si-B counterparts. The 7-μm thick Mo-Si-B coatings were shown to successfully withstand oxidation during short-time exposure for 10min at a temperature as high as 1700°C due to the formation of protective silica scale. The oxidation of Mo-Al-Si-B coatings was accompanied by the diffusion of aluminum to the coating surfaces and the formation of a single Al2O3 layer at 1200–1300°C and a double Al2O3-SiO2 layer at 1500°C which were less protective against oxidation. The surface oxidation processes were also accompanied by phase transformations inside the oxygen-free part of both Mo-Si-B and Mo-Al-Si-B coatings with the formation of MoB and Mo5Si3 phases.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The present paper gives a detailed description of structural changes in three types of MoCN–Ag coatings (Mo51C15N27Ag7, Mo40C31N23Ag6, and Mo43C14N40Ag3) during dynamic temperature ramp tribological ...tests with particular emphasis on the analysis of wear products to identify adaptive friction mechanisms in the temperature range between 250 and 550°C. Thorough structural characterization using high-temperature XRD, SEM, TEM, GDOES, and Raman spectroscopy provided evidence of various tribo-chemical reactions in the zone of tribological contact affecting lubrication. The coating lubrication in the temperature range between 100 and 400°C was observed to be different. Unlike Mo51C15N27Ag7 coating whose friction coefficient monotonously increased with increasing temperature from 25 to 250°C, the Mo40C31N23Ag6 coating demonstrated low values of friction coefficient up to 250°C due to the tribo-activated formation of carbon-based fibers normal to the sliding direction. The good lubrication of the Mo43C14N40Ag3 coating at elevated temperatures was attributed to almost no wear due to its high hardness and to the formation of a thin tribo-activated MoO3 film at 350°C. However, complete oxidation of the wear track at 400°C resulted in intensive abrasion wear and high friction. Above 400°C, all coatings demonstrated similar values of friction coefficient irrespective of phase composition (melt, Ag6Mo10O33, or MoO3+Ag).
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•Low-friction coatings for broad temperature range•Various tribo-chemical reactions in the tribological contact zones at elevated temperatures•Low friction coefficients due to tribo-activated formation of carbon-based fibers•Good lubrication of MoCN–Ag coatings at elevated temperatures due to almost no wear•Tribo-activated formation of silver molybdate rods with turbostratic structure at 550°C
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Powders of high-entropy Hf0.2Ta0.2Ti0.2Nb0.2Zr0.2C (HECZr) and Hf0.2Ta0.2Ti0.2Nb0.2Mo0.2C (HECMo) carbides were fabricated through the reactive high-energy ball milling (R-HEBM) of metal and graphite ...particles. It was found that 60 min of R-HEBM is adequate to achieve a full conversion of the initial precursors into a FCC solid solution for both compositions. The HECZr powder possesses a unimodal particle size distribution (40% d ≤ 1 μm, 95% d ≤ 10 μm), and the HECMo powder features a bimodal distribution with a slightly larger particle size overall (30% d ≤ 1 μm, 80% d ≤ 10 μm). Bulk high-entropy ceramics with a minor presence of an oxide phase were fabricated through the spark plasma sintering of these high-entropy powders at 2000 °C with a 10 min dwelling time. The HECZr ceramics possess a relative density of up to 94.8%, hardness of 25.7 ± 3.5 GPa, Young's modulus of 473 ± 37 GPa, and thermal conductivity of 5.6 ± 0.1 W/m·K. HECMo ceramics with a relative density of up to 93.8%, hardness of 23.8 ± 2.7 GPa, Young's modulus of 544 ± 48 GPa, and thermal conductivity of 5.9 ± 0.2 W/m·K were also fabricated. A comparison of the properties of the HECs produced in this study and those previously reported is also provided.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The Mo-Si-B, Mo-Zr-Si-B, and Mo-Hf-Si-B coatings were deposited by magnetron sputtering of the MoSi2-MoB, MoSi2-MoB-ZrB2 and MoSi2-MoB-HfB2 targets. The composition and structure of coatings were ...investigated by glow discharge optical emission spectroscopy, scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron and Raman spectroscopy. Mechanical properties were measured by nanoindentation method. The short-time oxidation resistance of coatings was evaluated at temperatures of 1100, 1300, and 1500 °C. The results showed that all coatings deposited onto alumina substrates were characterized by a dense columnar structure. Mo-Si-B coatings contained phases of hexagonal h-MoSi2 and amorphous a-MoB. With the addition of Zr and Hf, an increase in the lattice parameter and a decrease in the grain size of h-MoSi2 by 50 and 25%, respectively, were observed. The base Mo-Si-B coating had a high hardness of 30 GPa. The introduction of Zr and Hf led to a decrease in hardness by 24 and 20%, respectively. The Mo-Si-B coating was characterized by a minimal oxidation depth (<10 nm) at 1100 °C and 1300 °C, but a network of cracks that penetrated to the substrate was formed. Cracks on the surface of the Mo-Zr-Si-B and Mo-Hf-Si-B coatings were not observed; the formation of oxide layers, 0.3–2.0 μm thick, was revealed. The oxidation resistance of coatings at temperature of 1500 °C increased in direction Mo-Si-B → Mo-Hf-Si-B → Mo-Zr-Si-B. The best results for the Mo-Zr-Si-B coating were associated with a smaller grain size, higher thermal stability, and the formation of a protective layer based on SiO2 with the inclusion of ZrO2 crystallites.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This article reports the results of comparative studies of the composition, structure, high-temperature oxidation resistance, mechanical and tribological properties of (MoTaNbZrHf)-Si-B coatings ...prepared at an identical average power of 1 kW by direct current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HIPIMS). Switching from the DCMS to the HIPIMS mode is found to increase adhesion and crack resistance of the coatings and their wear resistance under friction sliding and cyclic impact conditions, as well as reduce the depth of oxidation at 1300 °C threefold. The record-breaking values of high-temperature oxidation resistance at 1500 °C are achieved due to formation of a surface film based on the borosilicate glass (a-Si:B:O) containing crystallites of the t-HfSiO4, o-Ta2O5, m-HfO2, and m-ZrO2 phases.
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•A multilayer target with a (MoTaNbZrHf)-Si-B working layer was produced.•DCMS and HIPIMS coatings exhibited a hardness of 13–14 GPa.•The transition from DCMS to HIPIMS improves crack- and wear resistance.•The coatings demonstrated high oxidation resistance at 1100–1500 °C.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Nanocrystalline Fe100–56.8Ti0–13.5B0–34.2 films 1.4 µm thick are prepared by dc magnetron deposition on glass substrates. The structure and magnetic properties of the films are comprehensively ...characterized and analyzed. The lattice parameter and the grain size of the bcc Fe-based phase (2-25 nm), parameters of the stochastic magnetic structure (the relative size and the effective anisotropy field of stochastic domains D1/2 and the local magnetic anisotropy field at the grain scale), saturation magnetization Ms, coercive field Hc, static permeability mst, and ferromagnetic resonance frequency fr of the films are quantitatively estimated and their interrelations are studied. As Ti and B contents increase, the phase composition of the films changes in accordance with the sequence αFe - αFe(Ti) - αFe(Ti) + TiB2 - amorphous, wherein Ms decreases from 2.1 to 0.3 T. The Hc values vary in the interval 7–70 Oe determined by the D1/2 field or by other magnetic anisotropy sources. The μst values vary in the interval 20–140. The μst values obtained by the Lorentzian dispersion law adequately fall within the range of the calculated permeabilities, which is limited by the coercive field obtained from the hysteresis loops and the anisotropy field determined by Kittel equation. The μst values of the films are kept up to the frequencies of at least 1.5 GHz. The frequency dependences of the permeability of the films are analyzed taking into account the influence of skin effect and are considered in terms of Acher’s law. The obtained values of the Acher’s constant (less than 0.3) indicate the possibility of reaching the higher values of μst and fr at the expense of elimination of the perpendicular anisotropy, in particular, via the formation of thinner films as compared to the films under study (1.4 µm thick). According to the available literature data, the presented investigations, using the FeTiB films as an example, were performed for the first time.
•Nanocrystalline Fe100–56.8Ti0–13.5B0–34.2 films are prepared by dc magnetron deposition.•As Ti and B contents increase, the phase composition changes from αFe to amorphous.•The magnetic structure of the films under study consists of stochastic domains.•The resonance frequencies correlate with the anisotropy fields of stochastic domains.•Static permeability falls within the range of calculated permeabilities.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Protective Zr-Si-B-N coatings were deposited by magnetron sputtering of the 66%ZrB2 + 26%ZrSi2 + 6%Si + 2%ZrO2 composite target at varied partial pressure of nitrogen. The coatings were studied in ...terms of structure, optical characteristics, mechanical and tribological properties, cyclic impact and oxidation resistance. All the coatings were characterized by a dense and defect-free structure, without any well-defined columnar elements. The base of the non-reactive Zr-Si-B coatings was the hexagonal ZrB2 phase with the crystallite size of about 20 nm. Nitrogen doping led to grain size reduction and coating amorphization. An increase in the nitrogen concentration leads to the formation of an amorphous phase а-Si(Zr)BN. The high content of nonmetallic bonds ensured the high transmittance (up to 90 %) in the visible and infrared spectral ranges for the coatings characterized by the maximum nitrogen content. Hardness of the coatings deposited in working gas Ar and Ar + 15%N2 was ~20 GPa. When the coatings were deposited in an atmosphere of pure nitrogen, this value was ≤15 GPa. Due to structure modification as well as increasing elastic recovery and elastic strain to failure, nitrogen doping of the coatings contributed to reduction of the friction coefficient and increased wear resistance under sliding friction conditions and cyclic impact loading. High-temperature oxidation resistance and thermal stability of the coatings decreased after nitrogen doping. The Zr-Si-B coating exhibited the highest oxidation resistance and withstood long-term exposure to 1200 °C and short-term exposure to 1400 °C. The high protective properties were ensured by formation of the silica-based surface protective layer with zirconia crystallites dispersed in it.
•The Zr-Si-B-N coating with the maximum N content had a high transmittance of ~90 %.•The increase in N2 flow rate led to a decrease friction coefficient and wear rate.•The coatings, obtained in Ar and Ar + 15%N2, retain protective properties at 1200 °C.•Zr-Si-B coating had the best oxidation resistance at 1400 °С.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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The processes of the pulsed magnetron sputtering (PMS) of multicomponent ceramic targets are studied upon deposition of functional coatings of various purposes. The regularities of changes in the ...structural characteristics, as well as mechanical and tribological properties, under increasing magnetron power frequency are studied. Summarizing the results obtained using the PMS technology upon the deposition of coatings using multicomponent SHS cathodes, the following conclusions can be drawn. a) The structure of coatings. Pulsed sputtering leads to the development of a denser and, at the same time, more defective structure with a high level of internal stresses and roughness. The effect of the pulsed mode on the grain size depends on the sputtering type and configuration of magnetic fields. For reaction sputtering, structural refinement is observed in some cases. The effect of increasing the thickness of reaction coatings due to the commencement of interaction between atoms sputtered from the target and nitrogen atoms at precipitation and minimization of target surface poisoning is found. b) Coating properties. The effect of a pulsed mode on the adhesion strength of coatings is reduced to its decrease. Dependences of hardness and other mechanical properties on the frequency of the pulse power have an extreme character with a maximum at 50 kHz. The use of low frequencies (50–150 kHz) leads to a decrease in the friction factor. At the transition to the pulsed mode, the friction factor stabilizes during the test and, in most cases, wear resistance increases.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Using the Cr
3
C
2
–NiAl cathode prepared by self-propagating high-temperature synthesis, Cr‒Ni–Al–C–N coatings are deposited by pulsed cathode arc evaporation in argon, nitrogen, and ethylene ...atmospheres. The coating structures are investigated by scanning electron microscopy, X-ray diffraction analysis, glow-discharge optical emission spectroscopy, and Raman spectroscopy. Mechanical and tribological properties are investigated by nanoindentation and pin-on-disk tribological testing. Anticorrosion properties are evaluated by voltammetry in the medium of a 1-N H
2
SO
4
solution. The nonreactive coating deposited in an inert Ar atmosphere contains the Cr
3
C
2
fcc phase with a size of crystallites below 20 nm. The deposition in the C
2
H
4
and N
2
reaction media leads to amorphization of the coatings. The samples deposited in argon and nitrogen exhibit high hardness values of 24–25 GPa. The deposition of coatings in C
2
H
4
gives rise to a 40% decrease in the hardness. However, the carbon-containing sample has a relatively low coefficient of friction at a level of 0.28, as well as better wear and corrosion resistances due to the positive effect of the diamond-like carbon phase.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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•TiNbCN–Ag coatings for wide temperature range tribological applications.•Alloying with Nb and Ag improve tribological properties and oxidation resistance.•Ag-rich TiNbCN coatings ...show friction coefficient below 0.45 in range of 25–700°C.•Ag-doped coatings show active oxidation protection and self-healing functionality.
Ag- and Nb-doped TiCN coatings with about 2 at.% of Nb and Ag contents varied between 4.0 and 15.1 at.% were designed as promising materials for tribological applications in a wide temperature range. We report on the structure, mechanical, and tribological properties of TiNbCN-Ag coatings fabricated by simultaneous co-sputtering of TiC0.5+10%Nb2C and Ag targets in comparison with those of Ag-free coating. The tribological characteristics were evaluated during constant-temperature tests both at room temperature and 300°C, as well as during dynamic temperature ramp tests in the range of 25–700°C. The coating structure and elemental composition were studied by means of X-ray diffraction, scanning and transmission electron microscopy, and glow discharge optical emission spectroscopy. The coating microstructures and elemental compositions inside wear tracks, as well as the wear products, were examined by scanning electron microscopy, energy-dispersive spectroscopy, and Raman spectroscopy. We demonstrate that simultaneous alloying with Nb and Ag permits to overcome the main drawbacks of TiCN coatings such as their relatively high values of friction coefficient at elevated temperatures and low oxidation resistance. It is shown that a relatively high amount of Ag (15 at.%) is required to provide enhanced tribological behavior in a wide temperature range of 25–700°C. In addition, the prepared Ag-doped coatings demonstrated active oxidation protection and self-healing functionality due to the segregation of Ag metallic particles in damage areas such as cracks, pin-holes, or oxidation sites.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
