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The ZrN/Zr/a-C multilayered coatings were deposited onto Ti6Al4V and Si substrates using a closed field unbalanced magnetron sputtering. The morphology and microstructure of the multilayers were performed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM). The multilayer consists of a-C layers, Zr layers and ZrN layers. The Zr interlayers can improve the weak adhesion between a-C layers and ZrN layers. The multilayer exhibits a low residual stress of − 0.5 GPa and a hardness of 18.7 GPa. The tribological properties were evaluated by a ball-on-disk tribometer. The friction coefficient and wear rate of the multilayer in fetal bovine serum (FBS) kept very low values during sliding at an applied load of 2 N, which indicated excellent long-term wear resistance. What is more, the multilayer also presented a low wear rate in FBS even at a high applied load of 10 N. Additionally, the corrosion resistance of Ti6Al4V in Hank's solution is significantly improved by the multilayer. This study demonstrates that the ZrN/Zr/a-C multilayer exhibits excellent performance including low residual stress, high corrosion resistance as well as good bio-tribological properties and it is proper to protect Ti6Al4V alloy. [ABSTRACT FROM AUTHOR]

A novel ionothermal strategy for developing a chemical conversion film on magnesium alloys is proposed based on the interaction of a deep eutectic solvent (DES) with the substrate. Upon heating the choline chloride/urea mixture-based DES can react with the AZ31B magnesium alloy surface to form a promising anti-corrosion conversion film. Interestingly, the chemical conversion film is mainly composed by MgH 2 and MgCO 3 phases. The as-grown conversion film exhibits superhydrophobicity after surface modification in a stearic acid/ethanol solution. Electrochemical tests and visual investigations indicate the corrosion resistance of the magnesium alloy can be improved by the conversion film. [ABSTRACT FROM AUTHOR]

Abstract: The collective influence of crucial electrodeposition parameters (temperature, deposition voltage and bath composition) on the properties of Zn–Ni films electrodeposited in a choline chloride–urea eutectic-based ionic liquid was investigated. The microstructures, chemical compositions, phase structures and corrosion behaviors of electrodeposited films were analyzed using scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction and linear cyclic voltammetry, respectively. The surface morphologies and chemical compositions of the films were strongly dependent on the electrodeposition parameters. It was found that the amounts of nickel in the Zn–Ni alloy films were significantly higher than that present in the electrolytes and was always above 50%, indicating normal codeposition mechanism. Electrodeposition of high Zn content alloy is favorable at high electrodeposition voltages, high temperatures and high Zn (II)/Ni (II) ratios. Electrochemical measurements shows that under the conditions considered, the Zn–Ni film from 0.45M Zn (II)–0.05M Ni (II) deposited at 55°C and 0.8V exhibits the highest barrier corrosion resistance compared with the other films and this was attributed to a dense, smooth and crack free morphology with optimum Zn content. [Copyright &y& Elsevier]

Abstract: A comparative study was carried out on the deposition mechanism, microstructure, and corrosion resistance of Cu films electrodeposited from the base electrolyte of CuCl2·2H2O in a choline chloride–ethylene glycol eutectic solvent with absence and presence of the additive of ethylene diamine (EDA). The base electrolyte is unstable and produces rough Cu films with columnar grains. Upon the introduction of EDA, the modified electrolyte becomes stable and the nucleation of Cu deposits is strongly inhibited, thus producing a smooth and compact surface with finer grains. Uniform corrosion and decreased corrosion current density are recognized in the fine grained Cu films. [Copyright &y& Elsevier]

Abstract: A fully dense nanocrystalline (nc) Ni film on the brass substrate was fabricated by a simple electrodeposition from a choline chloride-based ionic liquid (choline chloride–ethylene glycol) at working voltage (between the two electrodes) of 1.0V and room temperature. It is found that the nc Ni with an average grain size of about 6nm has a face-centered cubic crystal structure. At the film/substrate interface, the epitaxial growth of some nc Ni grains on brass grains can be evidenced by the high resolution transmission electron microscope. The 6nm grain sized Ni exhibits a high strain rate sensitivity (m =0.051) and enhanced hardness values in the range of 7.6–9.7GPa. The deformation mechanism of the nc Ni under indentation is also discussed with the theoretical model fitting. The potentiodynamic polarization curve shows that the nc Ni film exhibits a much negative corrosion potential, which provides a sacrificial anode protection for the brass substrate. [Copyright &y& Elsevier]

a-C/a-C:Ti multilayer films were deposited on medical Ti6Al4V alloy using a closed field unbalanced magnetron sputtering system with various substrate bias duty cycle. The tribological and corrosion behaviors of the multilayer films in Hank's solution were evaluated by a ball-on-disk tribometer and an electrochemical workshop. The duty cycle has a significant effect on the bonding structure, and mechanical and tribological properties of the films. The polarization resistance of the films on Ti alloy is approximately ten times more than that of Ti6Al4V which indicates that higher corrosion resistance can be achieved in Hank's solution at 37 °C. However, the polarization resistance and corrosion current do not change so much with the variation of duty cycle, implying that its influence on corrosion behavior of these a-C/a-C:Ti multilayer films is not so obvious. [ABSTRACT FROM AUTHOR]

Biomedical Ti6Al4V alloy exhibits excellent mechanical and anti-corrosion properties but poor wear resistance. In order to improve the combination performance of Ti6Al4V alloy, Zr-doped graphite-like carbon (GLC) nanomultilayer and nanocomposite coatings are deposited by magnetron sputtering. The microstructures of the coatings are characterized by transmission electron microscopy (TEM) and Raman spectroscopy. The Zr-doped GLC nanomultilayer shows low friction coefficient and wear rate at applied loads of 1 N and 3 N in Hank's solution. In addition, both the Zr-doped GLC nanomultilayer and nanocomposite coatings present high corrosion resistance, which results from the corrosion-resistant GLC and zirconium oxide. Compared to the Zr-doped GLC nanocomposite, the nanomultilayer is more promising in the applications under simultaneously tribological and corrosive conditions. [ABSTRACT FROM AUTHOR]

Abstract: An electroless Ni–P deposition process has been developed to treat the AZ91D magnesium alloy surfaces against corrosion. Magnesium alloy AZ91D was first phosphatized in a zinc phosphating bath containing molybdate. Then an electroless Ni–P deposition was carried out on the phosphate coating from a sulfate solution. The phases in the phosphate coatings were analyzed by XRD. Microstructures of phosphate coatings and electroless Ni–P depositions were observed by SEM and EDS. It was found that there was metallic zinc in the phosphate coating and the addition of Na2MoO4 in the phosphating bath resulted in the increase of zinc in the coating. A lot of disperse metallic zinc particles acted as the catalyst nuclei for the succeeding Ni–P deposition. Consequently, the Ni–P depositions with dense and fine microstructure were obtained on the phosphate coatings gained from the phosphating bath wherein 2.0∼2.5g/L Na2MoO4 was added. The Ni–P plus phosphate coatings on the AZ91D magnesium alloy exhibited acceptable corrosion resistance as shown by the results of the Salt Spray Corrosion Test. [Copyright &y& Elsevier]