The coupling effects of friction and corrosion significantly exacerbate the wear severity of components during prolonged service in marine environments. In this work, the modulation cycle thickness of soft/hard structure was regulated to fabricate multilayer thick diamond-like carbon coatings using filtered cathodic vacuum arc deposition technology with a high-angle (225 degrees) filtering bent pipe. The tribocorrosion resistance of multilayer DLC coatings was investigated by performing long-term sliding tests (10 h) under high loads (10 N and 20 N) in air and in 3.5 wt.% NaCl solution. The results show that the soft/hard layer structure can significantly relieve the residual stress (about 46.9 %) of the DLC coatings, and the hardness of the prepared multilayer DLC coatings of about 5 mu m thickness can be enhanced to more than 60 GPa. The tribocorrosion mechanism of multilayer DLC coatings in 3.5 wt.% NaCl solution is mainly mechanical fatigue wear making C-sp3 bond to C-sp2 bond conversion, leading to the generation and expansion of micropores. The lubricity of debris and solution mitigates coating wear much more than the coupling effect exacerbates coating wear, enabling the multilayer DLC coating to maintain tribocorrosion protection for a long period of time under high load conditions in 3.5 wt.% NaCl solution. Wear resistance and corrosion protection are critical for precision components in complex environments. Therefore, compared with the absence of deposited protective coatings, multilayer thick DLC coatings with soft/hard layer structures can effectively mitigate wear of precision components during prolonged use in complex environments (such as under high loads and in corrosive solutions), which provides an important reference value for their protective applications in marine environments.

AbstractPolyimides externally deployed in spacecraft or satellites extensively have various aerospace hazards, including atomic oxygen (AO) erosion, irradiation degradation, and electrostatic charge/discharge (ESC/ESD). To cope with these challenges, we fabricate a ZnO/CuNi‐polyimide composite film with augmented permanence. Using spectroscopy and microscopy techniques, we have shown that the combination of chelation and cross‐linking in the interfacial architecture leads to enhanced interfacial compatibility and mechanical robustness. Besides, due to the positive AO diffusion barrier ability of the wurtzite ZnO, our composite film shows remarkable AO resistance and a very small Ey value of 6.88 × 10−26 cm3/atom, which is merely 2.29% of that of pristine polyimide. Moreover, the well‐defined nanocrystalline state with minimal lattice swelling (0.3%–0.7%) of the Fe+‐irradiated ZnO/CuNi‐polyimide at a damaging dose of 353.4 dpa demonstrates its excellent irradiation resistance. Finally, the ZnO/CuNi‐polyimide also shows sufficient electrostatic dissipation capacity to cope with the ESC/ESD events. Our fabrication approach for composite films based on multi‐technology integration shows potential for aerospace applications and deployment.

To address corrosion and friction problems in complex environments, traditional protective coatings are gradually replaced by multicomponent coatings. In this work, a (TiAlCrSi)C multicomponent coating with ultralubrication (COF < 0.1) and excellent corrosion resistance was prepared by FCVAD technology with regulated C2H2 flow. The composition, structure, roughness, dry friction, corrosion and tribocorrosion of the (TiAlCrSi)C coating were analyzed. The results show that the (TiAlCrSi)C coating shows an amorphous structure, and the addition of carbon improves the degree of amorphization of the coating. Carbon exists in the form of carbide and amorphous carbon in the (TiAlCrSi)C coating, the carbon content saturation of the coating is about 70 at.%. The formed carbides and sp2-C in the (TiAlCrSi)C coating have extremely low COFs and good wear resistance. The high proportions of amorphous carbon and sp2-C improve the self-lubricating and nonmetallic properties of the (TiAlCrSi)C coating, which makes the coating have good tribocorrosion resistance in 5.0 wt% H2SO4 solution. The wear mode of the coating changes from abrasive wear to adhesive wear. Therefore, the (TiAlCrSi)C coating has great potential application value for tribocorrosion surface protection in a 5.0 wt% H2SO4 solution environment.

In this work, a novel CrAlNiYN coating was prepared by filter cathode vacuum arc (FCVA) technique. The evolution of the microstructure and properties of the coatings with varying N2 flow rates was systematically investigated. The results revealed that as the N2 flow rate increased from 10 to 90 sccm, the N content in the coating increased from 2.54 to 46.20 at.%, while the Ni content significantly decreased from 67.54 to 31.15 at.%. Simultaneously, the phase structure transitioned from the intermetallic compound AlNi3 to the solid solution Al (Cr)N. This transformation, along with solid solution strengthening and grain refinement, resulted an increase in hardness from 13.4 +/- 0.4 to 26.6 +/- 0.6 GPa. Moreover, the H/E, H3/E2 and W e values also displayed a gradually increasing trend, indicating improved resistance to plastic deformation. However, the adhesion strength presented a weakening trend from HF1 to HF3. Furthermore, the corrosion current density of coatings first increased and then slightly decreased with the increase of N2 flow rate, while the polarization resistance had the opposite trend of change. Among them, the coating at 10 sccm exhibited the best corrosion resistance, with the lowest i corr of 0.150 mu A cm- 2 and the highest Rp of 302.1 k Omega cm2.

A novel four-arc co-filter cathodic vacuum arc deposition technique which was optimized was introduced to deposit (AlCrMoTiV)Nx high-entropy alloy nitride films that were corrosion-resistant, high hardness and adhesion. The effect of nitrogen on the microstructure, corrosion resistance and mechanical properties of films was systematically investigated. As the N2 gas flow rate continues to increase, the phase structure of the (AlCrMoTiV) Nx films transforms from a body-centred cubic structure to an amorphous structure, and then to a nanocomposite structure with nano- crystallites embedded in the amorphous matrix. The hardness of the films is proportional to the ratio of N2:Ar and reaches maximum (34.08 GPa) at a ratio of 7:4. The adhesion of deposited films was higher than 20 N owing to the bombardment of the substrate by energetic ion beams during the deposition of coatings. The enhanced hardness at higher N contents is mainly gives rise to the combined effect of formation of strong metal-nitrogen bonding, solid solution strengthening, the formation of the nanocomposite structure and ion beam assisted bombardment strengthening. Furthermore, the excellent corrosion resistance can be obtained by the (AlCrMoTiV)Nx films.

A magnetically filtered cathode vacuum arc deposition system was used to deposit Ti-doped diamond-like carbon coatings (Ti-DLC) on pin surfaces to improve the wear resistance of high-power density diesel engine piston pins. The coating structure, composition, and morphology were characterised using field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and other techniques. Friction tests were carried out using a universal tribometer to study the tribological properties of pins with or without coatings under dry friction and oil lubrication. The surface morphology and cross-sectional morphology of the Ti-DLC coating show that the coating has a uniform cross-section and good surface properties. The XPS spectrum shows that the coating contains Ti-C, Ti-C*, sp2-C, sp3-C, and C-O/C=O. Raman spectroscopy shows that there is an amorphous carbon phase in the Ti-DLC coating. The friction test shows that the friction temperature increase of the pin with the Ti-DLC coating is lower than that without the coating, especially under dry-friction conditions. At the end of the test, the difference in temperature increase is 16.7%. The friction coefficient when using high-viscosity lubricating oil with a coating is relatively lower than that without a coating, especially under low-speed and heavy-duty conditions. In the dry-friction state, the coated surface has better wear resistance than the uncoated surface, which primarily manifests as abrasive wear, and the surface without a coating mainly experiences adhesive wear.

Convection diffusion equation is widely applied in many fields of science and technology. Many practical en-gineering problems can be expressed by this equation in unsteady state. However, it is usually difficult and time-consuming to find its solution. In this paper, a boundary type method named half boundary method (HBM) is proposed for two dimensional unsteady convection-diffusion equations. The main idea of HBM is introducing new variables to reduce the order of the equation and build relations of variables between nodes inside the area and nodes at half of the boundaries, namely the unknown variables. Since only variables at half of the boundaries are chosen as unknown variables, using HBM can realize dimensionality reduction and the maximum matrix order is less than that in finite volume method when considering large division number, which makes HBM fast and efficient. After the unknown variables are obtained by the boundary conditions, all variables at nodes can be obtained simultaneously according to the relations mentioned above. Numerical studies are carried out for convection dominated problems, problems with variable or discontinuous coefficient and problems with mixed boundary conditions, which show the validity of HBM for two-dimensional unsteady convection-diffusion problems and high accuracy for convection-domination problems.

Organic light-emitting diode devices (OLEDs) industry is developing rapidly, however, OLEDs are very sensitive to oxygen and water, determining how to achieve better barrier effect is one of the main challenges of flexible OLEDs technology. Based on the filtered cathode vacuum arc (FCVA) technology, a dense aluminum oxide (Al2O3) film with a thickness of about 100 nm was grown at room temperature for OLEDs encapsulation. The composition, structure, surface roughness, refractive index, light transmittance and other physical properties of the film were analyzed. The water vapor transmission rates (WVTRs) of the films were tested at 85 degrees C and 85% relative humidity (R.H.). Photoluminescence spectrum (PL) test was carried out to study the luminescence ability of tris(8-hydroxyquinoline) aluminum (Alq(3)) before and after the deposition of Al(2)O(3 )film. The results show that the amorphous Al(2)O(3 )film with dense structure prepared by FCVA has high visible light transmittance. The Al2O3 film reduces the WVTRs of the polyethylene naphthalate (PEN) film by four orders of magnitude and maintains the light-emitting performance of the organic light-emitting layer. These results indicate that the FCVA technology is a feasible method for preparing barrier films of flexible OLEDs.

In order to improve the tribological and tribocorrosion performance of Ti-DLC films, a series of Ti-DLC films were prepared by filtered cathodic vacuum arc technique by controlling C2H2 flow rate. The microstructure, mechanical properties, tribological and tribocorrosion performance of Ti-DLC films with different C2H2 flow rates were investigated. As the C2H2 flow rate increased from 10 to 140 sccm, the columnar cross-sectional structure of the Ti-DLC films transformed to dense and uniform structure. The increase in C2H2 flow rate also resulted in an initial increase followed by a decrease in hardness and compressive stress. The results showed that the Ti-DLC films on substrate can significantly improve its tribology, anti-corrosion and anti-tribocorrosion properties. Under dry friction condition, the film prepared at 20 sccm with hardness of 49.1 GPa showed low wear rate at a reciprocating frequency of 1 Hz under a load of 2 N (2 N/1 Hz), however, the film was worn through due to the high compression stress at 10 N/5 Hz. The film at 140 sccm showed great tribology performance with the lowest coefficient of friction of 0.017 and the lowest wear rate of 5.91 x 10(-8) mm(3)/N center dot m at 10 N/5 Hz, which was attributed mainly to the formation of sp(2)-carbon rich transfer layers on the counterpart. The tribocorrosion properties test demonstrated that the coating prepared at 140 sccm exhibited the best tribocorrosion resistance with the lowest coefficient of friction of 0.055, the lowest wear rate of 3.56 x 10(-7) mm(3)/N center dot m and high stable value of OCP of 0.116 V under the synergistic action of corrosion and friction.

To improve the anti-tribocorrosion property, and decrease the metal dissolution and wear of stainless-steel components caused by the synergistic action of corrosion and friction in marine environments, Ti-DLC coatings were obtained on steel substrate using a filtered cathodic vacuum arc (FCVA) system by adjusting bias voltage. The structure, mechanical properties, corrosion, and tribocorrosion behavior were investigated. Increasing the bias voltage from −50 V to −300 V, Ti content decreased from 23.9 to 22.5 at.%, and grain size decreased first, and then increased. Obvious TiC grains embedded in the amorphous carbon matrix were observed in the coating from the TEM result. Hardness increased from 30.23 GPa to 34.24 GPa with an increase in bias voltage from −50 to −200 V. The results of tribocorrosion testing showed that the Ti-DLC coatings at −200 V presented the best anti-tribocorrosion performance with the smallest friction coefficient of 0.052, wear rate of 2.48 × 10−7 mm3/N∙m, and high open-circuit potential, which is mainly due to the dense structure, high value of H/E* and H3/E*2, and great corrosion resistance. Obtained results suggest that the Ti-DLC coating with nanocomposite structure is a potential protective material for marine equipment.

Metal bipolar plates (BPPs) are candidates with great promise to replace conventional carbon-based BPPs. However, the drawbacks caused by the corrosion and passivation of metal bipolar plates need to be addressed urgently. In present study, corrosion-resistant and interfacial conductive high-entropy alloy and ceramic coatings possess great potential in the application of surface modification of bipolar plates in proton exchange membrane fuel cells (PEMFCs). An original co-filtered cathodic vacuum arc deposition (C-FCVAD) is designed to prepare AlTiVCrMo high-entropy alloy (HEA) and (AlTiVCrMo)Nx high-entropy ceramic (HEC) coatings with different nitrogen content, and their feasibility as surface modification methods of bipolar plates is investigated by analyzing the microstructure, corrosion properties, interfacial conductivity and hydrophobicity of the coatings. The obvious body-centered cubic (BCC) structure can be observed in HEA coating, and amorphous structure is gradually formed as the nitrogen content increases to 28.12 at. %. Finally, polycrystal structure is formed when nitrogen content reached the maximum. The electrochemical corrosion and interfacial contact resistance (ICR) results significantly demonstrate that the coatings have enhanced corrosion resistance and conductivity. The bipolar plates with AlTiVCrMo HEA and (AlTiVCrMo)Nx HEC coatings as surface modification methods have good application potential in PEMFCs operating environment.

The corrosion behaviors of TA2 titanium were investigated by in situ electrochemical measurements in a solution of 2.3 ppm Li+ and 1500 ppm B3+ at a temperature of up to 300 °C. The morphology, phase structure, and composition of the oxide film, after 800 h exposure time in a solution at 300 °C and 14 MPa, were characterized by scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), etc. The growth mechanism of the oxide film based on the activation energy was discussed. The potentiodynamic polarization and electrochemical impedance spectroscopy analyses showed that the corrosion resistance of titanium significantly weakened when increasing the solution temperature from 30 to 300 °C, but it increased in the initial stage of holding time (0–66 h) at 300 °C, then gradually decreased (66–378 h), and reached a stable state after 378 h. The oxide film, which was about 5 μm thick, consisted of anatase phase and a small amount of B2O3. The growth mechanism is a combination of layer by layer and island growth.

Hydrogen-free diamond-like carbon (DLC) films with thickness of 36 μ m and 50 μ m have been prepared on Si and AISI 304L stainless steel substrates, respectively, by filtered cathodic vacuum arc (FCVA) together with a high-voltage pulse power. The structure, chemical bonding state, mechanical properties and wear, corrosion resistance and anti-erosion performance were evaluated. The thick DLC films with compressive stress of 0.71 GPa and hardness of 3160 HV were obtained. The preparation of the low stress but high hardness coating mainly due to the appropriate high negative bias and short pulse duration, which could result in an alternate ion bombardment and deposition. The 50 μ m-thick coating showed corrosion resistance with high polarization resistance of 4.69 × 10 8 Ω·cm 2 and low corrosion current density of 5.47 × 10 −8 A·cm −2 . Thick coating exhibited outstanding sand particle erosion resistance with low average mass loss rate of 0.035 mg g −1 . Under high-speed sand erosion conditions, the coating remains unbroken, without peeling or cracking were observed on the erosion center. In addition, DLC coatings showed good tribological performance under dry, water- and oil-lubricated condition.

Flexible hard coatings with high density, high surface integrity and smooth surface morphology exhibit simultaneously high hardness, high toughness and high crack resistance which represent a new class of high-performance coatings. However, their depositions are a hard work. Deep oscillation magnetron sputtering (DOMS) is a novel high-power impulse magnetron sputtering, which has become a hotspot in tribological hard coatings around world. Using a series of modulated micro-pulse of voltage oscillation, DOMS can achieve virtually arc-free high-power discharge to generate highly ionized target species to obtain high dense plasma with low ion energy and high ion flux, These features allow preparing high-performance nanostructured coating, which can be modulated by composition, structure and properties using a series of micro-pulse under optimized deposition conditions. In this paper, we summarized characteristics of flexible hard nanostructured coatings and research progress in recent years of flexible hard nanostructured coatings deposited by DOMS technology.

In this work, amorphous hydrogenated carbon and titanium carbide composite (a-C: H/TiC) films are deposited on titanium bipolar plates which are used in proton exchange membrane fuel cells (PEMFCs). It was fabricated by high power pulsed magnetron sputtering (HiPIMS) with TiN and TiCN transition layers. The microstructure results indicated that the titanium element was introduced in the films with a form of titanium carbide, and the increasing ID/IG values imply the graphitization of films. Amorphous carbon with a large content of sp2 hybrid bonds leads to an excellent conductivity of 1.6 m omega.cm2 at 1.4 MPa and improves the corrosion resistance by inhibiting the growth of columnar crystal. In addition, a number of sp2-riched clusters on the surface enhance the hydrophobicity of the film. The a-C: H/TiC films prepared in this work significantly improved the hydrophobicity, corrosion resistance and interfacial conductivity of titanium bipolar plates, showing a great potential for applications in PEMFCs.

Coating crack and interfacial delamination are recognized as two critical factors inducing spallation of thick diamond-like carbon (DLC) coatings. The effect of the two factors is found to dramatically accelerate the failure of thick DLC coatings. However, there are few reports on the effect of interfacial delamination on coating crack. In this work, in order to investigate the evolution of the coating crack and interfacial delamination, as well as the effect of interfacial delamination on coating crack, a finite element model that combines the bilinear cohesive zone model and the extended finite element method (XFEM) is established. It is found that the occurrence of interfacial delamination triggers a second expansion of coating crack. Factors influencing the degree of interfacial delamination on coating crack can be modulated by coating thickness and coating elastic modulus. As the coating thickness increases, the length of interfacial delamination increases, and thus the propagation of coating crack is accelerated. In contrast, the increase of coating elastic modulus could reduce the length of interfacial delamination, which consequently weakens its influence on the propagation of coating crack.

High-performance coatings originated in ingenious coating designs and advanced preparation techniques are expected to fulfill imperious demands in propulsion, bearings and mechanical seals, etc in marine systems for seawater lubrication. In this work, TiSiCN nanocomposite coatings were deposited by high power impulse magnetron sputtering at a power of 4–8 kW. As power is increased, TiSiCN coatings possess nanocrystalline (TiN, TiC, TiCN)/amorphous (Si3N4, SiC, sp2-C) nanocomposite structure without distinctly preferred orientation. The highest hardness (H) of 43 GPa and effective Young’s modulus (E*) of 360 GPa were achieved at 8 kW, while the highest H/E* of 0.123 and H3/E*2 of 0.61 appear at 7 kW due to refined nano-grains, uniform distribution, high surface/interface integrity and fully dense microstructure. Rockwell C adhesion level increased from HF2 at 4 kW to HF1 at 8 kW. TiSiCN coatings with high H, H/E*, H3/E*2 and adhesion exhibit high open circuit potential of −0.07 V, low friction coefficient of 0.25 and specific wear rate of 4.78 × 10−5 mm3 N−1 m−1, resulting from mild abrasive wear without the occurrence of pitting corrosion in 3.5 wt.% NaCl aqueous solution. Moreover, cycling tribocorrosion tests revealed that passive films possess strong abilities of regeneration and self-repairation on sliding contact surface.

Tribological properties of CrN/TiN superlattice coatings deposited on IN 718, WC-6%Co and Si(100) by the combined deep oscillation magnetron sputtering were investigated. The results show that the coating growth is independent of the nature of substrate materials. As the hardness of substrate materials is increased, the scratch critical loads increase. Adhesion failure mode changes from buckling failure to cooperative deformation of substrate/coating system with only small cracks in the whole scratch track. Wear mechanism of the coatings deposited on IN 718 and WC-6%Co changes from abrasive and oxidative wear to mild abrasive wear under a normal load of 2 N. Under a normal load of 4 N, the coatings on IN 718 suffer severe oxidative wear, while the coatings on WC-6%Co suffer the combined abrasive and oxidative wear. The production, accumulation and mass transfer of oxides result in the oscillation of friction coefficient during dry sliding wear tests.

Three CrN coatings were deposited on the Inconel X750 through the metal vapor vacuum arc ion implantation and the magnetic filtered cathodic vacuum arc deposition system (MEVVA-FCVA) with the N2 flow rates of 10, 50, and 100 sccm, respectively. The surface morphologies and cross-section morphologies of the CrN coatings were obtained through scanning electron microscopy (SEM) and an optical profilometer. The microstructures of the coatings were characterized through X-ray diffraction (XRD). The hardness and the elastic modulus of the coatings were tested by a nano-hardness tester. The adhesion strength and friction coefficients were investigated through scratch tests and ball-on-disk tests and the wear tracks were tested by the optical profilometer. The experimental results indicate that the CrN coating deposited on the Inconel X750 substrate displays a uniform thickness and a smooth surface. The mechanical properties behaves well as the N2 flow rate varies. The CrN coating significantly reduces the friction coefficient fluctuation and improves the antiadhesion and anti-wear properties of the Inconel X750.