VN Coatings Research Articles

The Green Lubricant Coatings Deposited by Physical Vapor Deposition for Demanding Tribological Applications: A Review

The emergence of nanotechnology and surface engineering techniques provides new opportunities for designing self-lubricant coatings with enhanced properties. In recent years, green coating technologies have played a vital role in environmental preservation. This article mainly reviews five typical types of self-lubricant coatings including MoN coatings, VN coatings, WN coatings and TMN (Transition Metal Nitride) soft-metal coatings, and DLC (Diamond-like Carbon) with lubricant agents deposited by PVD (Physical Vapor Deposition) for the demanding tribological applications, which is the latest research into the green lubricant coatings. Furthermore, it is of great significance for designing the green self-lubricant coatings to adapt the demanding tribological applications to meet the industrial requirements.

Optical emission spectroscopy of vanadium cathodic arc plasma at different nitrogen pressure

Optical emission spectroscopy studies of vanadium plasma in a cathodic-arc discharge in a nitrogen atmosphere have been carried out. Spectral lines of neutral atoms and ions of the cathode material V, V1+, and V2+, and nitrogen N2 and N2+ were observed in the discharge plasma. Analysis and comparison of the intensity of vanadium and nitrogen spectral lines as a function of nitrogen pressure showed that in vacuum excited ions V2+ and V+ are registered, with increasing pressure, the lines V+*, N2*, and N2+* are observed, and at pressures above 0.5 Pa, the neutral vanadium lines are additionally registered. The electron temperature of Te decreases from 5.9 to 3–4 eV with increasing pressure. Studies of cross-sectional scanning electron microscopy images of VN coatings deposited at different nitrogen pressures have shown that a dense, homogeneous, fine-grained microstructure is formed in the coating when the number of neutral V in the plasma is low, while in the presence of a large number of neutrals, the coating structure changes to a dense structure with columnar growth.

Influence of Magnetron Sputtered TiN and VN Coatings on the Electrical Impedance of Aluminium Electrodes

In this work, TiN and VN coatings were applied on aluminium electrodes by direct current (DC) magnetron sputtering in order to study the influence of the protective coatings on the electrical impedance of the substrate. The structure of the samples was studied using X-ray diffraction (XRD). The microhardness of the substrate and the coated samples was also determined. The electrical impedance of the substrates with and without coatings was also studied and the results were used for evaluation of the applicability of such coatings for interface electrodes for flexible electronics. Electric impedance spectroscopy in a wide frequency range was applied for interlayer and surface contact properties determination. Results showed improved stability and conductivity of the electrodes coated using the TiN and VN thin films, particularly in the low frequency range.

Effect of Nitrogen Pressure and Substrate Bias Voltage on Structure and Mechanical Properties of Vacuum Arc Deposited VN Coatings

The binary vanadium–nitrogen (V–N) coatings were formed using cathodic arc evaporation. Two sets of coatings were produced using: (a) nitrogen pressure (pN2) from 0.001 Pa to 3 Pa at a constant substrate bias voltage (UB) of − 100 V and (b) a substrate bias voltage from − 50 to − 300 V at a constant nitrogen pressure of 1.5 Pa. The influence of the above parameters on the coating properties, in particular on the insufficiently investigated and described adhesion of the coatings to the substrate, was demonstrated. The phase transformation V → V + V2N → V + c-VN → h-VN → h-VN + c-VN and c-VN → h-VN occurs for coatings formed with increasing nitrogen pressure and substrate bias voltage, respectively. With the increase in pN2 and UB, an increase in coating hardness and adhesion to the substrate is observed, as well as an improvement in wear resistance.

Thermostability, oxidation, and high-temperature tribological properties of nano-multilayered AlCrSiN/VN coatings

In this study, monolithic AlCrSiN, VN, and nano-multilayered AlCrSiN/VN coatings were deposited using a hybrid deposition system combining arc ion plating and pulsed direct current magnetron sputtering. The microstructure, thermostability, mechanical, oxidation and tribological properties of the coatings were comparably investigated. The multilayered AlCrSiN/VN coating exhibited a face-centered cubic (fcc) structure with (200) preferred orientation and showed the highest hardness (30.7 ± 0.5 GPa) among these three coatings due to the multilayer interface enhancement mechanism and higher compressive stress. The AlCrSiN sublayers effectively prevented the V element from rapid outward diffusion to the surface of AlCrSiN/VN coating at elevated temperatures, which improved the oxidation resistance of the coating. Decomposition of V (Cr)–N bonds occurred at annealing temperatures from 800 °C to 1000 °C and V2N phase appeared at 1100 °C. The AlCrSiN/VN coating showed excellent tribological performance at high temperatures by combining the merits of VN layers for low friction coefficient and AlCrSiN layers for superior oxidation resistance. Compared to VN and AlCrSiN coatings, AlCrSiN/VN coating showed the lowest wear rate of 2.6×10-15 m3/N·m at 600 °C and lowest friction coefficient of 0.26 at 800 °C with a relativity low wear rate of 39.4×10-15 m3/N·m.

Understanding corrosion and tribology behaviors of VN and VCN coatings in seawater

VN and VCN coatings were prepared using multi-arc ion plating technique on 316L stainless steel and single silicon substrates. Microstructures, mechanical performances, corrosion behaviors and tribology properties of VN and VCN coatings in the atmosphere, distilled water and seawater were contrastively tested. It was confirmed that the VCN coating had a typical nanocystallite/amorphous structure. Moreover, the hardness increased from 30.5 to 36.5 GPa and the corrosion current density decreased from 2.16 × 10−6 to 0.82 × 10−6 A cm−2 after carbon was doped into the VN coating. Compared with the VN coating, the VCN coating had the lowest friction coefficient of 0.26 and wear rate of 0.68 × 10−6 mm3 Nm−1 in seawater, which could be ascribed to the lubrication of graphitization transfer film and improvement of the comprehensive performance.

Properties of VN Coatings Deposited by ICP Assisted Sputtering: Effect of ICP Power

Properties of VN Coatings Deposited by ICP Assisted Sputtering: Effect of ICP Power

유도결합 플라즈마 파워가 VN 코팅막의 미세구조, 결정구조 및 기계적 특성에 미치는 영향에 관한 연구

The effects of ICP (Inductively Coupled Plasma) power, ranging from 0 to 200 W, on the crystal structure, microstructure, surface roughness and mechanical properties of magnetron sputtered VN coatings were systematically investigated with FE-SEM, AFM, XRD and nanoindentation. The results show that ICP power has a significant influence on coating microstructure and mechanical properties of VN coatings. With the increasing of ICP power, coating microstructure evolves from a porous columnar structure to a highly dense one. Average crystal grain size of single phase cubic fcc VN coatings was decreased from 10.1 nm to 4.0 nm with increase of ICP power. The maximum hardness of 28.2 GPa was obtained for the coatings deposited at ICP power of 200 W. The smoothest surface morphology with Ra roughness of 1.7 nm was obtained from the VN coating sputtered at ICP power of 200 W.

The microstructure and phase evolution of cone-like VN coating in a wide temperature range

Abstract The cone-like VN coatings were deposited on the surface of Si (100) substrate by RF magnetron reactive sputtering and their oxidation behavior was investigated in ambient air at temperatures ranging from 25 to 700 °C. The phase structure, surface morphologies and oxidation mechanism were studied using EPMA, SEM, XPS and TEM. The results reveal that there are three stages for the oxidation of cone-like VN coating. From 25 to 300 °C, the cone-like structure of VN coating has no change although a few cracks appeared due to the formation of V2O3 scales. The V2N phase could transform to V2O3 or VN phases. From 300 to 600 °C, the cracks start to expand and become more, meanwhile some grains start to grow and becomes irregular shape. The VN phase transforms to V2O3 and V2O5. Some formed V2O3 phase also transforms to V2O5. From 600 to 700 °C, the cone-like structure disappears although the grain boundaries are still apparent. The VN phase transforms to V2O5 and no V2O3 phase forms.

Structure and properties of Si-implanted VN coatings prepared by RF magnetron sputtering

VSiN coatings with silicon content ranging from 0 to 19.8at.% were deposited by reactive magnetron sputtering technique. The structure, mechanical, tribological properties and corrosion performance were investigated. The results show that VSiN coatings consist of a mixture of fcc-VN, h-V2N, amorphous Si3N4 phases with slight (111) preferential orientation. The hardness, H/E and H3/E2 ratios of VSiN coatings first increase and then decrease and the maximum values are 27GPa, 0.098 and 0.325GPa, respectively, at 10.2at.% Si. The friction coefficient and wear rate first decrease and then increase with increasing the silicon content. The minimum values of 0.35 and 5.1×10−6mm3·N−1mm−1 are obtained at 10.2at.% Si, respectively. The corrosion resistance of the substrate coated with VN or VSiN coatings is superior to the bare substrate.

Carbon doping to improve the high temperature tribological properties of VN coating

VN and VCN coatings were deposited by the cathodic arc ion plating technique. Microstructures, mechanical properties and tribological properties of both coatings in ambient air were comparatively investigated. Results showed that the sp2C–C, sp3C–C and VC phases were found in VCN coating. The VCN coating exhibited lower friction coefficients and wear rates than VN coating in different temperatures. The lower friction coefficient and better anti-wear property of the VCN coating were closely related to the self-lubricating amorphous carbon and V2O5 phase, indicating its potential application as a lubricant coating for tribo-components under high temperature conditions.

Enhancing the wear resistance of magnetron sputtered VN coating by Si addition

Although Si addition into transition metal nitrides has been long known to enhance hardness of coatings, relatively less evidence indicates that the hardness gain can be translated into a significant improvement of wear resistance as expected. The reported wear rates of TM–Si–N coatings are generally greater than 10−16m3/Nm. Here, we prepared VSiN coatings by adding Si into VN coatings, and investigated the friction-wear behavior of the VSiN coatings which achieved wear rates on the 10−17m3/Nm order of magnitude. The friction-wear behavior was studied by ball-on-plate sliding tests against Al2O3 balls (3 or 6mm in diameter), followed by microscopic examination on the worn surfaces. For the VN coating mild wear transited to fatigue failure after ~104 sliding cycles with crack growth and propagation, whereas the VSiN coatings retained mild wear more than 105 cycles, in which the sliding wear proceeded predominately by tribo-oxidation removal mechanism. The enhanced wear resistance of the VSiN could be mainly attributed to their special nanocomposite structure that limited intergranular cracks, and then suppressed fracture-dominated wear. Based on the results, it was proposed that the resistance to fracture-dominated wear could be taken into account for developing low-wear transition-metal nitride coatings.

Angle-resolved X-ray reflectivity measurements during off-normal sputter deposition of VN

VN coatings were deposited by reactive sputtering at different deposition angles χ. The thin film growth was monitored by angle-dispersive in situ X-ray reflectivity measurements. These measurements were realized using a monochromatic X-ray beam and exploiting its angular divergence. Already during deposition of the first few nm, the measurements revealed the formation of a porous coating with stable growth rate. The growth rate decreased with increasing tilt angle. The reduction was less than expected from the flux projection onto the sample surface. This can only partially be explained by the porosity increase with increasing tilt angle. SIMTRA simulations confirmed that the deposition rate is strongly influenced by the interplay between deposition geo-metry and particle transport.

Thermodynamic Analysis of Chemical Vapor Deposition of the VN Coating

The VN coatings were coated by chemical vapor deposition on T12 substrate using V2O5, H2 and N2 as reactants. Thermodynamic calculation and analysis of formation reaction of VN were done by thermodynamic potential function. As shown by the experimental results, chemical vapor deposition of the VN coating with preheating temperature of 973K and deposition temperature of 1573K under normal atmospheric pressure was feasible.

Influence of Nitrogen Partial Pressure and Substrate Bias on the Mechanical Properties of VN Coatings

Vanadium nitride coatings were deposited via magnetron reactive sputtering system with varying nitrogen partial pressures and negative substrate bias to further understand the influence of the sputtering conditions on the microstructure and the mechanical performance. Grazing incidence X-ray diffraction, field emission scanning electron microscopy equipped with energy dispersive X-ray and X-ray photoelectron spectroscopy were used to characterize the microstructure; nano-hardness tester and profilometer were used to measure the mechanical performance. By varying the nitrogen partial pressures from 0.007Pa to 0.29Pa, more compact coating with higher hardness (22.9GPa) was achieved at 0.29Pa. In parallel, the influence of bias voltage on the residual stress and hardness was significant.

Electronic property and bonding configuration at the TiN(111)/VN(111) interface

Multilayered TiN(111)/VN(111) coatings find many technological applications where the behaviors of their inside interfaces are known or suspected to influence functionalities in such an engineering surface system. Here, we demonstrate, by first-principles calculations on energetics and electronic structures of a total of 36 candidate interfaces, that the preferred geometries (i.e., that having the largest adhesion energy) are those that retain the interface structures as in either of the nitride bulks both atomically and electronically. Using several analytic methods, we have thoroughly characterized electronic states and determined that the interfacial bondings are mainly ionic, yet maintain a small amount of covalent character. The theoretical calculations presented provide insight into the complex electronic properties of the functional TiN/VN interface that could be difficult to obtain by experiment alone but which are practically important for further understanding and improvement of such a multilayered coating at the atomic scale.

Deposition and Characterization of Hard Coatings in the Material System V–Al–N by Reactive Magnetron Sputter Deposition

AbstractBinary and ternary hard coatings in the system V–Al–N were deposited with varying substrate bias at substrate temperatures around 350 °C by reactive d.c. and r.f. magnetron sputtering in an Ar/N2 gas mixture from a V and/or Al target. For each experiment, Si (100) and polished 1.2379 steel substrates were placed on the rotating substrate table. VN coatings were deposited at a constant Ar flow of 250 sccm, while the bias voltage was varied between −80 and −200 V. The influence of this variation on the mechanical properties hardness and reduced elastic modulus was examined by microindentation and the critical load of failure by scratch test, friction coefficient was determined by ball‐on‐disc tribometer tests. For the deposition of AlN and VAlN coatings bias voltage, Ar/N ratio and the total pressure were varied. The chemical composition of the obtained coatings was determined by electron microprobe analysis and the crystal structure of the films was characterized by X‐ray diffraction.

Erosion-resistant coatings for gas turbine compressor blades

The effect of ion-plasma coatings made from high-hardness metal compounds on the erosion and corrosion resistance and the mechanical properties of alloy (substrate) + coating compositions is comprehensively studied. The effects of the thickness, composition, deposition conditions, and design of coatings based on metal nitrides and carbides on the relative gas-abrasive wear of alloy + coating compositions in a gas-abrasive flux are analyzed. The flux contains quartz sand with an average fraction of 300–350 μm; the abrasive feed rate is 200 g/min; and the angles of flux incidence are 20° (tangential flow) and 70° (near-head-on attack flow). Alloy + coating compositions based on VN, VC, Cr3C2, ZrN, and TiN coatings 15–30 μ m thick or more are shown to have high erosion resistance. A detailed examination of the coatings with high erosion resistance demonstrates that a zirconium nitride coating is most appropriate for protecting gas turbine compressor blades made of titanium alloys; this coating does not decrease the fatigue strength of these alloys. A chromium carbide coating is the best coating for protecting compressor steel blades.

Increase of hardness and oxidation resistance of VN coating by nanoscale multilayered structurization with AlN

AlN/VN nanoscale multilayered coatings with various bilayer periods from 2.1 nm to 10.0 nm have been prepared by alternating deposition of AlN and VN. The maximum hardness, 45.4 GPa, was obtained for the AlN/VN nanoscale multilayered coating with bilayer period of 2.1 nm, which is an increase of 54% over the rule of mixture hardness value (29.5 GPa) of AlN and VN coatings. The mass gain of heat-treated AlN/VN nanoscale multilayered coating at temperatures from 600 °C to 700 °C in air was measured to be less than that of the VN single layered coating, which indicates that the oxidation resistance as well as hardness of the VN coating can be increased by nanoscale multilayered structurization with AlN.

The Beneficial Effect of High-Temperature Oxidation on the Tribological Behaviour of V and VN Coatings

The mechanisms for frictional self-adaptation of advanced hard coatings with optimum tribological properties are based on the formation of thin reaction films in sliding contacts. The aim of this work was to characterize VN and V coatings deposited by unbalanced magnetron sputtering and to determine the influence of oxide phase formation on their friction and wear properties during high-temperature exposure in ambient air. Dry sliding experiments were performed in the temperature range between 25 and 700 °C. Structural changes and oxide phases were identified by X-ray diffraction and Raman spectroscopy after tribometer testing. The friction coefficient of the V coatings decreases from about 1.05 at RT to 0.27 at 700 °C, while the VN coating has a lower coefficient of friction (∼0.45) at RT which further decreases at temperatures above 400 °C. The onset of rapid oxidation of V and VN coatings, as evidenced by differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA), occurred at 400–450 °C with the formation of vanadium oxides, which were identified by XRD as V2O5, VO2 and V6O13. For both coatings evaluated, a significant decrease of the friction coefficient at temperatures above 400 °C was observed reaching a value of 0.25–0.27 at 700 °C, due to the formation of V2O5, giving rise to solid lubrication, and subsequent melting of this phase at temperatures above 600 °C, leading to liquid lubrication.