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The surface characteristics of biomaterials play an important role in their interaction with biological systems. Tantalum (Ta) oxides and their coatings have been proved to increase their applications in the biomedical fields such as medical devices and dental implants by improving their osseointegration and corrosion resistance. In this study, Ta and amorphous tantalum oxide coatings were deposited by using magnetron sputtering. A hydrophilic crystalline β-Ta 2 O 5 coating was obtained by rapid thermal annealing of the deposited tantalum oxide coating at 700 °C. In this study, Staphylococcus aureus and Actinobacillus actinomycetemcomitans ( A. actinomycetemcomitans ) are Gram-positive and Gram-negative bacteria, respectively, that exhibit physiological commensalism on the human skin and oral areas. Both bacteria were chosen as the model for in vitro anti-bacterial analyses by a fluorescence staining method employing Syto9. The cytocompatibility of human skin fibroblast cells (CCD-966SK) on the coatings was also determined using an MTT assay. It showed that the amorphous tantalum oxide coatings possessed good antibacterial performance, while the hydrophilic crystalline tantalum oxide coatings exhibited outperformed human skin fibroblast cellular biocompatibility. [ABSTRACT FROM AUTHOR]

Abstract: The high-temperature oxidation behavior of the CrN and Cr–Al–Si–N coatings was studied. These coatings were deposited on silicon substrates by using a cathodic-arc deposition system with lateral rotating arc cathodes. Chromium and Al88Si12 cathodes were used for the deposition of Cr–Al–Si–N coatings. The deposited Cr0.38Al0.56Si0.06N exhibited higher hardness of 41±2GPa and higher H3/E*2 ratio of 0.468GPa than CrN due to the introduction of Al and Si to form a nanocrystalline structure. For the high-temperature oxidation test, the coated samples were annealed at 800°C in air for 2h. The Cr0.38Al0.56Si0.06N possessed much lower oxidation rate as measured by the oxide layer of the coatings. The addition of Al and Si in the coating may inhibit the formation of Cr2N phase and grain coarsening as found in the deposited CrN coating. In addition, the coexisting Al2O3 and SiO2 near the surface retarded the diffusion of oxygen into the Cr0.38Al0.56Si0.06N. The deposited Cr0.38Al0.56Si0.06N showed an oxidation behavior superior to the CrN. The high-temperature oxidation resistance of the CrN coatings can be improved by the formation of nanocomposite Cr–Al–Si–N. [Copyright &y& Elsevier]

Abstract: The plasma in a cathodic arc evaporation process used for the deposition of Cr1−x O x films was studied by an optical emission spectroscopy (OES). With the introduction of Ar and oxygen into the chamber at deposition pressures from 0.7 Pa to 2.7 Pa, high density of evaporated chromium catalyzes the decomposition of oxygen reactive gas, and induces the formation of Cr1−x O x films. Optical emission spectra including atomic and ionized Cr, excited and ionized oxygen revealed that excitation, ionization and charge transfer reactions of the Cr–O plasma occurred during the Cr1−x O x deposition process. A simplified empirical model which incorporates the relevant atomic processes in the gas phase with the chemical composition and deposition rate of the deposited Cr1−x O x coating was developed. Rhombohedral Cr2O3 and tetragonal CrO2 were observed in the Cr1−x O x coatings deposited at higher pressure than 1.3 Pa. The Cr1−x O x coating depicted a dense and compact microstructure with well-attached interface. [Copyright &y& Elsevier]

Abstract: The monolayered TiSiN and multilayered TiSiN/CrN were synthesized by cathodic arc evaporation. The Ti/Si (80/20 at.%) and chromium targets were used as the cathodic materials. With the different I [TiSi]/I [Cr] cathode current ratios of 1.8, 1.0, and 0.55, the multilayered TiSiN/CrN coatings possessed different multilayer periods (Λ) of 8.3 nm, 6.2 nm, and 4.2 nm. From XRD and TEM analyses, both the monolayered TiSiN and multilayered TiSiN/CrN revealed a typical columnar structure and B1-NaCl crystalline, no peaks of crystalline Si3N4 were detected. Among the multilayered TiSiN/CrN coatings, the multilayered coating with Λ =8.3 nm possessed higher hardness of 37±2 GPa, higher elastic modulus of 396±20 GPa and the lower residual stress of −1.60 GPa than the monolayered (Ti0.39Si0.07)N0.54 coating(−7.25 GPa). Due to the higher Cr/(Ti+Cr+Si) atomic ratio, the multilayered TiSiN/CrN with Λ =5.5 nm possessed the lowest friction coefficient. But the lowest of wear rate was obtained by the multilayered TiSiN/CrN with Λ =8.3 nm, because of higher H3/E⁎ 2 ratio of 0.323 GPa. The monolayered TiSiN possessed the highest wear rate of 2.87 μm2/min. Therefore, the mechanical and tribological property can be improved by the design of multilayered coating. [Copyright &y& Elsevier]

Abstract: Chromium carbide and chromium oxide coatings deposited by physical vapor deposition methods have been successfully applied in molding industries for their excellent tribological performances. In addition, nanocomposite coatings have recently attracted interest because of their high hardness, wear resistance, and good thermal and chemical stability. In this study, Cr–C–O/a-C nanocomposite coatings were synthesized by cathodic-arc evaporation with plasma enhanced duct equipment. A pure CO2 reactive gas was introduced to react with chromium to form Cr–C–O/a-C nanocomposite coatings during the deposition process. The atomic content ratio of O/(C+O) increased with increasing CO2 deposition pressure. A nanocomposite structure of coexisting Cr2O3 and Cr7C3 crystallites and amorphous carbon phases was found in the Cr–C–O/a-C coatings. The nanoindentation test revealed the nanocomposite Cr–C–O/a-C coatings with the highest atomic content ratio of O/(C+O) possessed the highest hardness of 23 GPa. [Copyright &y& Elsevier]

Abstract: Ti1−x Si x N coatings were synthesized by cathodic arc evaporation with plasma-enhancing filter duct, using Ti80Si20 alloy target as cathodes. Optical emission study revealed that excitation, ionization and charge transfer reactions of the Ti-Si-N plasma occurred during the Ti1−x Si x N deposition process. The chemical content of Si varied from 3.3 to 6.0at% in Ti1−x Si x N depending on the nitrogen partial pressure of the reaction chamber. All the Ti1−x Si x N coatings displayed a NaCl structure and a preferred (200) orientation parallel to the substrate surface. Among the studied Ti1−x Si x N coatings, the Ti1−x Si x N with 6at.% Si possessed the highest hardness of 45GPa and H 3/E*2 ratio of 0.527GPa, indicating the best resistance to plastic deformation. We found that the structure and mechanical properties of the Ti1−x Si x N films were correlated with the nitrogen pressure and silicon content of the coatings. [Copyright &y& Elsevier]

Abstract: Ternary TiCrN and nanocomposite TiCr(C,N)/amorphous carbon (a-C) coatings with different carbon contents (0–26.6 at.%) were synthesized by cathodic arc evaporation with plasma enhanced duct equipment. The structural, chemical, and mechanical properties of the deposited films were studied by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and nanoindentation measurement. The atomic content ratios of carbon/(Ti+Cr) and carbon/nitrogen increased with increasing C2H2 flow rate. A nanocomposite structure of coexisting metastable hard TiCr(C,N) crystallites and amorphous carbon phases was found in the TiCr(C,N)/a-C coatings, those possessed smaller crystallite sizes than the ternary TiCrN film. XPS analyses revealed the concentration of a-C increased with increasing carbon content from 8.9 at.% to 26.6 at.%. Exceeding the metastable solubility range of carbon within the TiCrN lattice, the carbon formed a-C phase in the deposited coatings. The nanocomposite TiCr(C,N)/a-C coatings exhibited higher hardness value of 29–31 GPa than the deposited TiCrN coating (26±1 GPa). It has been found that the structural and mechanical properties of the films were correlated with the carbon content in the TiCr(C,N)/a-C coatings. [Copyright &y& Elsevier]

Abstract: Multilayered TiAlN/CrN as well as monolayered CrN and TiAlN coatings were synthesized by cathodic arc evaporation with plasma enhanced duct equipment, using Cr and Ti50Al50 alloy cathodes. Optical emission spectra including atomic and ionized Ti, atomic Al and Cr, excited and ionized nitrogen (N2, N2 +, and N2 2+) revealed that excitation, ionization and charge transfer reactions of the Ti–Al–N and Cr–N plasma occurred during the multilayered TiAlN/CrN coating process. The preferred orientation was changed from (200) in CrN and TiAlN monolayered coatings to (111) plane in the multilayered TiAlN/CrN coatings. The multilayered TiAlN/CrN films had smaller crystallite size than the monolayered CrN and TiAlN films. The multilayered TiAlN/CrN coating with periodic thickness of 18 nm exhibited the highest H 3/E*2 ratio value of 0.193 GPa, indicating the best resistance to plastic deformation, among the studied CrN, TiAlN and multilayered TiAlN/CrN coatings. The multilayered TiAlN/CrN coatings also showed the best adhesion strength during scratch tests. It has been found that the structural and mechanical properties of the films were correlated with the multiple cathode design and nanolayer thickness. [Copyright &y& Elsevier]

During physical vapor deposition (PVD), bias voltage is usually applied to the substrate for tuning the ion energies and tailoring the coating structure and mechanical properties of a protective hard coating for specific applications. In the present study, AlTiN/CrTiSiN multilayer coatings were deposited by a multisource cathodic arc ion deposition system with negative substrate bias voltages ranging from −20 to −180 V. During the coating process, graded CrN, CrN/AlTiN and CrTiSiN were deposited as interlayers to enhance adhesion strength of the coatings. Multisources of Cr, TiSi and AlTi alloy targets were used. Residual stresses and mechanical properties of AlTiN/CrTiSiN multilayer coatings deposited under various bias voltages were investigated. All the AlTiN/CrTiSiN multilayer coatings possessed higher hardness values (38.2–39.6 GPa) than AlTiN (32.5 GPa). As compared to the monolithic AlTiN, which had high residual stress of −9.8 GPa, the AlTiN/CrTiSiN multilayer coatings showed lower residual stresses of −2.4~ −9.1 GPa. The higher bias voltage was used the higher residual stress was observed. The AlTiN/CrTiSiN multilayer coating deposited at −20 V possessed the lowest residual stress (- 2.4 GPa). A cyclic impact test with high frequency were performed to evaluate the impact fatigue performance. The AlTiN/CrTiSiN multilayer coating deposited at −20 V showed the highest H/E (0.082) and H3/E2 (0.265) values to resist impact fatigue. The design of AlTiN/CrTiSiN multilayer coatings via low bias voltage can decrease residual stress and possessed good impact fatigue performance. Although the AlTiN/CrTiSiN coating deposited at high bias voltage of −180 V had similar hardness value to other AlTiN/CrTiSiN coatings under −20 V and −100 V, worse resistance to impact fatigue were found. • AlTiN/CrTiSiN multilayer coatings were deposited by cathodic arc ion deposition. • Different negative substrate bias voltages ranging from −20 to −180 V were used. • All the multilayer coatings possessed higher hardness values than AlTiN. • The AlTiN/CrTiSiN coating deposited at −20 V exhibited the lowest residual stress. • The multilayer coating deposited at −20 V showed the highest H/E to resist impact fatigue. [ABSTRACT FROM AUTHOR]

The adhesion strength and mechanical properties of hard coatings on substrates can be improved by adding an interlayer, which is also known as an adhesion, buffer, or seed layer. Cathodic-arc deposition (CAD) of hard coating often results in residual stresses, and the optimized design of the hard coating interlayer helps to reduce residual stress and improve mechanical properties, which is expected to extend the useful life of high speed precision stamping die applications. AlTiCrN transition metal nitride has been used as a protective hard coating because of its high hardness (~36 GPa) and resistance to high temperature oxidation up to 1100 °C. In this study, multicomponent hard coatings of AlTiCrN and AlTiCrN/TiSiN, which in the form of AlTiCrN/TiSiN multilayers, were deposited by cathodic-arc deposition. During the coating process, gradient TiN and CrN were deposited, respectively, as interlayers with different structures to control the residual stress and adhesion strength between the coatings and substrates. AlTiCr and TiSi alloy targets were used to deposit hard AlTiCrN/TiSiN coatings. The multicomponent AlTiCrN/Ti and AlTiCrN/Cr with Ti and Cr interlayers showed high residual stresses of −8 GPa and −8.4 GPa, respectively. The multilayered AlTiCrN/TiSiN coating with intermediate CrN and transition AlTiN/CrN multilayers under the top AlTiCrN/TiSiN multilayers possessed the lowest residual stress (−3 GPa). The residual stress changed by modifying interlayer configuration before the top AlTiCrN/TiSiN multilayers. The design of AlTiCrN/TiSiN multilayered coatings with interlayers of CrN and AlTiCrN/CrN can decrease residual stress and possessed good impact fatigue performance, which can be effective to reduce damage and cracking of hard coatings during cyclic impact loading. • AlTiCrN and multilayered AlTiCrN/TiSiN coatings with different interlayers were deposited. • The single-layer AlTiCrN with Cr interlayer showed the highest residual stress. • The multilayered AlTiCrN/TiSiN coating possessed the lowest residual stress. • The multilayered AlTiCrN/TiSiN possessed good impact fatigue performance. [ABSTRACT FROM AUTHOR]

Surface modification of steel has been reported to improve hardness and other mechanical properties, such as increase in resistance, for reducing plastic deformation, fatigue, and wear. Duplex surface treatment, such as a combination of plasma nitriding and physical vapor deposition, achieves superior mechanical properties and resistance to wear. In this study, the plasma nitriding process was conducted prior to the deposition of hard coatings on the SKH9 substrate. This process was done by a proper mixture of nitrogen/hydrogen gas at suitable duty cycle, pressure, and voltage with proper temperature. Later on, the deposition of gradient AlCrSiN coatings synthesized by a cathodic-arc deposition process was performed. During the deposition of AlCrSiN, CrN, AlCrN/CrN, and AlCrSiN/AlCrN were deposited as gradient interlayers to improve adhesion between the coatings and nitrided steels. A repetitive impact test (200k–400k times) was performed at room temperature and at high temperature (~500 °C) to assess impact resistance. The results showed that the tribological impact resistance for the synthesized AlCrSiN increased because of a progressive hardness support. The combination of plasma nitriding and AlCrSiN hard coatings is capable of increasing the life of molding dies and metal forging dies in mass production. [ABSTRACT FROM AUTHOR]