Enhanced corrosion resistance of layered double hydroxides/steam coating composite coating prepared by the hydrothermal method on LA43M magnesium–lithium alloy substrates

An excellent anticorrosion Mg–Al layered double hydroxide (LDH) composite coating was successfully fabricated on LA43M magnesium alloy substrates via an in situ steam coating (SC) process and a subsequent hydrothermal treatment at different temperatures. The microstructure, composition and phase formation of the composite coatings were studied via X-ray diffractometer, energy disperse spectroscopy, and scanning electron microscope, respectively. The corrosion resistance of composite coatings was further investigated using electrochemical measurements and corrosion test. The results showed that LDH/SC composite coating has typical nanosheets microstructure, which effectively seal the defects of SC. As the hydrothermal temperature increases, the thickness and density of nanosheets increases, and the corrosion resistance was significantly improved. Especially, the Mg–Al LDH/SC composite coating prepared at 100°C was the most dense and thickness, and exhibited the optimal and long-term anticorrosion resistance in 3.5 wt.% NaCl soultion. It has the lowest I_corr (1.767 × 10⁻⁸ A/cm²), which decreased by three and two orders of magnitude compared with the bare substrate and SC. Furthermore, it can maintain good chemical stability after immersion in the corrosion medium for 192 h and its hydrogen evolution rate (0.00416 mL·cm⁻²·h⁻¹) and weight lost rate (0.00266 mg·cm⁻²·h⁻¹) were the lowest compared with other samples.     

多色钛阳极氧化膜的耐蚀性研究

钛阳极氧化膜由于其特殊的性能而得到广泛作用。在此通过测量钛阳极氧化膜在０．０５ｍｏｌ／Ｌ氢氟酸溶液中的腐蚀电位随时间的变化以研究其耐蚀性。分析了膜层厚度、膜的形成温度及时间对其耐蚀性的影响。     

Wear-corrosion behavior of ultra-thin diamond-like carbon nitride films on aluminum alloy

Diamond-like carbon films exhibit high hardness, high wear resistance and a low friction coefficient. They are extensively utilized in the mechanical, electronic and biomedical industries. This work evaluates the effect of the thickness of ultra-thin diamond-like carbon nitride films on their corrosion properties and their wear-corrosion resistance in a mixed 1 M NaCl + 1 M H₂SO₄ solution using electrochemical methods. The corrosion current density and weight loss of all films during and after wear-corrosion test are also recorded. This work employs ion beam-assisted deposition (IBAD) to deposit DLC nitride films of various thicknesses (1.5, 2.0, 2.5 and 3.0 nm), containing 60% nitrogen gas in the form of a gaseous mixture of C₂H₂ + 60%N₂. The thickness of the films was measured using a transmission electron microscope (TEM). The atomic bonding structures of these DLC nitride films are analyzed using a Raman spectrometer and by electron spectroscopy for chemical analysis (ESCA). A scanning electron microscope (SEM) was adopted to elucidate the surface morphologies of the specimens after corrosion and wear-corrosion. The results indicated that all of the nitrogen-containing DLC films excellently protected the 5088 Al–Mg alloy substrate with an electroless plated Ni–P interlayer against corrosion, and that the degree of protection increases with the thickness of the film. In the wear-corrosion tests various potentials were applied during wear in the particular corrosive solution. The results further demonstrated that the wear-corrosion resistance of all the nitrogen-containing DLC films was as effective as corrosion protection, and that the wear-corrosion loss decreased as the film thickness increased.     

电流密度对Ti 6Al 4V微弧氧化膜形貌和性能的影响

采用NaAlO2-Na3PO4-NaF溶液体系,研究了电流密度对Ti 6Al 4V合金微弧氧化膜厚度、生长速率、表面形貌、粗糙度、组成相以及氧化膜耐蚀性、耐磨性等影响.结果表明,(1)在试验的电流密度范围内,氧化膜的厚度随电流密度的增大呈线性增大,但氧化膜的粗糙度却几乎呈指数增大,表面质量变差;(2)在质量分数为3.5%的NaCl溶液中显示了比Ti 6Al 4V钛合金更好的耐蚀性;(3)在干摩擦条件下,氧化膜的摩擦系数高于基体的,氧化膜的磨损机制为脆性断裂.     

The tribological performance of BCN films under ionic liquids lubrication

Boron carbon nitride films were deposited onto silicon substrates by medium frequency magnetron sputtering from graphite and boron targets with Ar and N₂ as feedstock. The three elements of B, C and N were bonded to each other and an atomic-level hybridized B–C–N had been formed in the films. The tribological performances of the boron carbon nitride film with 1-butyl, 3-methylimidazolium tetrafluoroborate ionic liquid as lubricant and the electrochemical corrosive behaviors of the BCN film were investigated. The boron carbon nitride film demonstrated excellent tribological properties and corrosion resistance as compared with diamond like carbon film. An extensive discussion of the effect of film intrinsically structure on both lubrication and corrosion under ionic liquid condition is given. In addition, the interrelation between the tribological properties and corrosion resistance is illustrated.     

Microstructure,mechanical and tribological properties of TaCN composite films by reactive magnetron sputtering

In this paper, a series of TaCN composite films with different carbon content were deposited by the magnetron sputtering system and the microstructure, mechanical and tribological properties were investigated. The results showed that the deposited TaCN films exhibited a three-phase of face-centered cubic (fcc) Ta(C,N), hexagonal closed-packed (hcp) Ta(C,N) and amorphous CNx. With the increase of carbon content, the hardness of the TaCN films first increased and then decreased, after reaching a maximum of 33.1 GPa; the adhesion strength increased gradually; the coefficient of friction decreased monotonically and the wear property initially improved and then weakened at room temperature. The coefficient of friction of the TaCN film at 28.21 at.% carbon decreased first, then increased and then decreased again and its high-temperature wear rate first decreased slightly and then increased, as the temperature increased from room temperature (RT) to 600 °C. The TaCN film at 28.21 at.% carbon exhibited excellent an elevated-temperature tribological properties.     

Temperature Dependence of Diamondlike Carbon Film Tribological Characteristics

The tribological characteristics of a diamondlike carbon (DLC) film deposited on high-speed steel were investigated systematically by using a ball-on-flat reciprocating tribometer over a range of temperatures (from −40° to 20°C). The results indicated that the temperature dependence of the DLC film's tribological behavior was associated with the counterpart material. DLC presented favorable tribological behavior while sliding on itself. However, when a steel ball slides against the DLC film, there is evidence that the heat generated has a significant impact on friction and wear. Microanalysis of wear tracks on the films showed that multiple wear mechanisms took place during testing. At higher temperatures, material transfer dominated the wear behavior, while fatigue-induced microcracking was the predominant wear mechanism at low temperatures. Raman analysis indicated that the DLC film was mechanically worn rather than removed by tribochemical interactions between the friction pairs.     

Effect of Annealing Temperature and Alumina Particles on Mechanical and Tribological Properties of Ni-P-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Composite Coatings

In this study, the effect of annealing temperature and alumina particles on micro-hardness, corrosion, wear, and friction of Ni-P-Al₂O₃ composites coating is studied. The electroless nickel composite coating with various alumina particle content is deposited on a mild steel substrate. The corrosion behaviour and tribological behaviour (wear and friction) of the composite coated samples are investigated and compared with Ni-P coated samples. The micro-hardness, wear resistance, and corrosion resistance of the composite coating improved significantly after heat treatment (400 °C) and in the presence of alumina particles. The composite coating deposited with alumina particle concentration of 10 g/L in an electroless bath and heat treated at 400 °C shows excellent results compared to Ni-P, as-deposited Ni-P-Al₂O₃ coating and coatings heat treated at different annealing temperature (200 °C, 300 °C, and 500 °C). Microstructure changes and composition of the composite coatings due to incorporation of alumina particles and heat treatment are studied with the help of SEM (scanning electron microscopy), EDX (energy dispersive X-ray analysis and XRD (X-ray diffraction analysis).     

Corrosion,wear and wear–corrosion behavior of graphite-like a-C:H films deposited on bare and nitrided titanium alloy

This work presents a comparative wear, corrosion and wear–corrosion (the last one in a simulated physiological solution) study of graphite-like a-C:H (GLCH) films deposited on bare and nitrided Ti6Al4V alloy. Films, deposited by r.f. PACVD, presented low porosity and promoted high corrosion resistance. The friction coefficient of the films was very low with appreciable wear resistance at room conditions. However, due to the simultaneous action of both load and the corrosive environment in wear–corrosion tests a marked reduction in the coating lifetime was observed. Unexpectedly, films deposited on the nitrided alloy presented a lifetime at least ten times shorter than that of films on bare alloy. We explain such a result in terms of film/substrate interaction. The weak GLCH/nitrided alloy interaction facilitates fluid penetration between the film and the substrate which leads to a fast film delamination. Such an interpretation is supported by force curve measurements, which show that the interaction between GLCH and nitrided alloy is four times weaker than that between GLCH and bare alloy.     

Tribomechanical and microstructural properties of cathodic arc-deposited ternary nitride coatings

Sintered carbides are promising materials for surfaces that are exposed to extreme wear. Owing to their high service load, ceramic-based thin films are coated on carbides using different techniques. In this study, non-toxic and cobalt-free powder metallurgy-sintered carbide samples were coated with TiN, TiAlN, CrAlN, and TiSiN ceramic-based thin film coatings by cathodic arc physical vapor deposition. The microstructure (phase formation, coating thickness, surface roughness, and topography), mechanical properties (hardness, modulus of elasticity, and plasticity indices), and tribological properties (nanoscratch and wear behavior) of the thin film coatings were investigated. No cracks or defects were detected in these layers. The ceramic-based ternary nitride thin film coatings exhibited better mechanical performance than the TiN coating. The TiN thin film coating had the highest average surface roughness, which deteriorated its tribological performance. The ternary nitride thin film coatings exhibited high toughness, while the TiN thin film coating exhibited brittle behavior under applied loads when subjected to nanoscratch tests. The wear resistance of the ternary nitride coatings increased by nearly 9–17 times as compared to that of the TiN coating and substrate. Among all the samples investigated, the substrate showed the highest coefficient of friction (COF), while the TiSiN coating exhibited the lowest COF. The TiSiN thin film coating showed improved mechanical and tribological properties as compared to other binary and ternary nitride thin film coatings.     

Simultaneous enhancement of hardness and wear and corrosion resistance of high-entropy transition-metal nitride

Binary transition-metal nitrides (TMNs) are widely used as protective coating materials, and enhancing key performance characteristics are crucial to improving their robust and durable applications in harsh service environments. Compositional modulation via multiple elemental species offers an effective approach for optimizing physicochemical properties of TMNs, and establishing the composition–property relation is essential to the design of high-performance TMNs. In this work, we report on a comparative study of our synthesized NbN, NbMoN, and (NbMoTaW)N films and examined their microstructure, mechanical properties, and tribological and corrosion behaviors. The high-entropy (NbMoTaW)N film exhibits the highest hardness of 23.5 ± 1.35 GPa, which is ascribed to its high structural stability, increased elastic constant, and elastic modulus compared to the NbN and NbMoN films. The (NbMoTaW)N film also possesses the best wear resistance stemming from the highest H/E ratio and formation of self-lubricating MoO₃ and WO₃ species; moreover, this film shows the best corrosion resistance attributed to the sluggish diffusion of Cl⁻ due to lattice contraction and the structural stability caused by high-entropy effect. This work demonstrates simultaneously enhanced hardness and wear and corrosion resistance in a high-entropy TMN, opening a pathway for developing a new generation of advanced protective coating materials.     

类金刚石薄膜在人工关节摩擦副表面改性进展

类金刚石（DLC）薄膜由于其优异的减摩耐磨性以及良好的生物相容性被引入到人工关节材质中。该文综述了DLC薄膜在人工关节摩擦副表面改性的研究现状,包括DLC薄膜的分类和制备方法。尽管该薄膜已被研究数十年,但在人体复杂的生理力学环境中高负荷摩擦腐蚀等综合作用下,仍存在高内应力导致结合力不足,从而限制其在人工关节领域的应用。该文介绍了降低DLC薄膜内应力提高膜基结合力的方法和DLC薄膜生物相容性的研究进展。最后,对不同DLC薄膜人工关节摩擦副的研究进展进行了阐述。根据该综述,提出厚的无氢DLC涂层（高sp3含量）,且在两个滑动表面上均有DLC薄膜的人工关节副具有优异的耐磨性,对于承重植入体应用至关重要。     

Improving the mechanical and tribological properties of amorphous carbon-based films by an a-C/Zr/ZrN multilayered interlayer

Amorphous carbon (a-C) films have been widely investigated to reduce the wear of medical implants due to their excellent tribological performance; however, the high internal stress of a-C films generated during the fabrication process remains an important scientific problem. Herein, we report novel a-C-based films with an a-C/Zr/ZrN multilayered interlayer. Our results reveal that, with increasing thickness of the multilayered interlayer, the hardness of the films decreased while their toughness and adhesion were improved. The Zr layers could act as a ductile phase, providing a toughening effect. A film with a 2:1 thickness ratio of multilayered interlayer to a-C top layer exhibited favorable tribological properties at various applied loads, especially at high applied load. The results indicated that by introducing a multilayered interlayer into a-C based films, the toughness and adhesion could be significantly improved without adversely sacrificing hardness. The tribological properties could be optimized by carefully tailoring the thickness ratio of multilayered interlayer to a-C top layer.     

Effects of Ti ion deposition on corrosion resistance of WE43 alloy

Ti films with different thicknesses were successfully deposited on the surface of WE43 alloy by filtered cathode vacuum arc technology, and the microscopic morphology, structural composition, and corrosion resistance of the films were studied by means of X-ray diffractometer, X-ray photoelectron spectroscopy and scanning electron microscope. The results show that when the deposition time of Ti ions is 800 s, the thickness of the Ti film is 2.35 μm, the surface of the film is dense, and there are few defects. Meanwhile, Ti800 alloy has the best corrosion resistance among the four modified alloys. It has a corrosion current density (I_corr) of 2.9 μA·cm⁻², which is about 50 times lower than that of unmodified alloy. This conclusion is also confirmed by the complete film layer of Ti800 alloy and the tight bonding with the substrate after immersion experiments. Good corrosion resistance is attributed to a dense and relatively chemically stable TiO₂/Ti structure in simulated body fluid corrosive media.     

Mechanical,tribological and electrochemical behavior of Zr-based ceramic thin films for dental implants

To determine the possibility of using new thin films architectures as biocompatible materials, an experimental and computational study was performed to evaluate the mechanical, tribological, and corrosion properties in simulated physiological media (saliva and blood plasma) of Zr, ZrN, and ZrN/Zr coatings, deposited by PVD magnetron sputtering. The crystalline structure and chemical composition were well correlated with high resistance to plastic deformation, wear, and corrosion, making these materials excellent candidates for functionalizing and protecting dental prostheses. The predominant wear mechanism under consideration was abrasion, which was reduced when using ceramic ZrN coating as a base for the superficial Zr thin film. When exposed to simulated body fluids, these materials exhibited high corrosion resistance, which was demonstrated by potentiodynamic measurements. These results are consistent with those predicted by Density Functional Theory computational models, which showed that electron transfer associated with the wear mechanism is kinetically impeded, as a consequence of the large energy barriers for this process associated with the adsorption of the molecular species on the ZrN surface. Additionally, calculated adsorption energies indicated that urea (from the simulated saliva solution) interacts strongly with the surface. This interaction was associated to the formation of passivating protective layers, which is a key mechanism to protect against corrosion, acting in synergy with the kinetic barriers.     

铝锰合金表面直流反应磁控溅射制备氧化铟锡薄膜

采用直流反应磁控溅射在AlMn合金表面制备出ITO薄膜.采用扫描电镜、X射线衍射、紫外-可见光测试、磨损试验、盐雾试验、薄膜厚度测量和显微硬度试验等方法对制备的ITO薄膜表面进行检测分析.结果表明:在溅射功率210 W、衬底温度120℃、溅射时间20 min的条件下,AlMn合金表面的ITO薄膜晶粒尺寸细小,与基底结合良好,AlMn合金表面光泽度好,强度、硬度高,并具有一定的耐磨、耐蚀性能.     

Preparation,characterization and properties of Cr-incorporated DLC films on magnesium alloy

Cr-incorporated diamond-like carbon (Cr-DLC) films were deposited on AZ31 magnesium alloy as protective coatings by a hybrid beams deposition system, which consists of a DC magnetron sputtering of Cr target (99.99%) and a linear ion source (LIS) supplied with CH₄ precursor gas. The Cr concentration (from 2.34 to 31.5 at.%) in the films was controlled by varying the flow ratio of Ar/CH₄. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to investigate the microstructure and composition of Cr-DLC films systematically. An electrochemical system and a ball-on-disk tribotester were applied to test the corrosion and tribological properties of the film on the AZ31 substrate, respectively. At low Cr doping (2.34 at.%), the film mainly exhibited the feature of amorphous carbon, while at high doping (31.5 at.%), chromium carbide crystalline phase occurred in the amorphous carbon matrix of the film. In this study, all the prepared Cr-DLC films showed higher adhesion to AZ31 than the DLC film. Especially for the film with low Cr doping (2.34 at.%), it owned the lowest internal stress and the highest adhesion to substrate among all the films. Furthermore, this film could also improve the wear resistance of magnesium alloy effectively. But, none of the films could improve the corrosion resistance of the magnesium alloy in 3.5 wt.% NaCl solution due to the existence of through-thickness defects in the films.     

Sealing effects of anodic oxide films formed on Mg-Al alloys

Mg alloys were anodized in alkaline NaOH solutions with various additives as a non-chromate method. Specimen AZ91 was anodized at a potential that produced a strong surface dissolution reaction and generated a large amount of Mg(OH)₂. The effect of sealing after anodizing was investigated, focusing on the effects of sealing time, temperature and solution conditions. The current density decreased with increasing A1(OH)₃ concentration in 1 M NaOH solution during anodizing; sparking occurred at potentials above 80 V. The best corrosion resistance with anodizing in 1 M NaOH solution occurred at a potential of 4 V, which caused the strongest active dissolution reaction. The sealing effect improved with increasing time and temperature, and corrosion resistance was proportional to the relative ratio of Mg(OH)₂. If the oxygen thickness observed by EDX equaled the film thickness, the film formed at 4 V in 1 M NaOH was 10–15 Μm thickness. The optimum corrosion resistance in sealing at various solutions after anodizing was 1M-NaOH solution.     

Corrosion and tribological properties of ultra-thin DLC films with different nitrogen contents in magnetic recording media

The corrosion spot density and contact–start–stop tribological properties that correlate to mechanical properties, electrical resistivity and lubricant bonded ratio of DLC overcoats on different disks of various surface roughness were investigated. DLC overcoats of hydrogenated carbon (CH) and nitrogenated carbon (CN) films were deposited by ion beam deposition (IBD) and sputter, respectively. Results show that the intensity ratio I(D)/I(G) increases with decreasing IBD-CH film thickness and increasing N₂ concentration of sputtered-CN layer, which implies that the films prepared at higher N₂ concentration contain a relatively lower sp³ bonded carbon. The composite hardness and Young's modulus of DLC films decrease with decreasing IBD-CH thickness and increasing N₂ concentration of sputtered-CN layers. Compared to disk overcoats deposited with only IBD-CH of comparable thickness, the lubricant bonded ratio is dramatically increased from 12 to 30% when the 0.5 nm CN is deposited on IBD-CH film. By increasing the N₂ concentration in the CN layer from 10 to 50 at.%, the electrical resistivity decreased from 3.6 to 0.8 kΩ and the lubricant bonded ratio increased from 30 to 46%. The corrosion spots density of sputtered-CN film surface decreases with increasing N₂ concentration. It is concluded that the dual layer of 1.5 nm IBD-CH/0.5 nm sputtered-CN with 30% N₂ deposition has the best integrated performance of corrosion resistance and CSS tribological properties.     

Preparation and properties of modified graphene oxide incorporated waterborne polyurethane acrylate

In this study, a new modifier (KPG) was prepared by modifying graphene oxide with γ‐glycidoxypropyl trimethoxysilane (KH560) and polydimethylsiloxane (PDMS). KPG was in turn added to aqueous urethane acrylate for the fabrication of waterborne polyurethane polyacrylate emulsion modified with KH560‐PDMS composite (KPG/WPUA). Textural characterizations of the KPG/WPUA coating were achieved via Fourier transform infrared, SEM, TGA and AFM techniques, which revealed that the KPG/WPUA film possessed a smooth surface. The synthesized KPG/WPUA films were tested for mechanical properties, hydrophobicity and acid/water corrosion performance which suggested their highly hydrophobic surface. KPG/WPUA with 0.1% KPG showed a contact angle of 118.35°, 30.35° higher than that of pristine WPUA. The KPG/WPUA film exhibited higher thermal stability, i.e. a 5% weight loss temperature of 305 °C, which was 30 °C higher than that of pristine WPUA film. The Young's modulus and elongation at break of the KPG/WPUA film were 34.1 MPa and 74.88% respectively, which were higher than that of WPUA film. Furthermore, KPG/WPUA films exhibited greater resistance (without obvious blistering and the white spotting phenomenon) to H₂O₂, HCl and water corrosion than pristine WPUA. The superior performance of KPG/WPUA films was attributed to the network chain structure formed upon the introduction of KPG into WPUA. The outstanding performance of KPG/WPUA films in terms of mechanical properties, thermal stability and high resistance to acidic and water corrosion makes them interesting alternative contenders for target applications. © 2019 Society of Chemical Industry