The influence of Ti plasma etching pre-treatment on mechanical properties of DLC film on cemented carbide

The pre-treatment of substrate surface had been a key part of DLC film preparation to improve mechanical and tribological properties. Ti plasma etching pre-treatment was investigated in this paper as a new effective surface pre-treatment method to substitute transition layer. This pre-treatment used high-energy Ti plasma to impact substrate surface. Ti plasma etched the substrate to a depth of 407 nm and increased the roughness from 1.36 to 40.39 nm. A trace layer of substrate, together with cobalt, oxides, and other impurities, was removed. Ti plasma broke some top WC crystals and combined with the free carbon ions separating from the substrate. A DLC film was deposited on the etched surface. Compared with DLC films deposited on the untreated substrate and Ti transition layer, the DLC film on the Ti plasma etched substrate had best adhesion strength of 34.14 N. The three DLC films had the same sp³ bonding carbon content, but Ti plasma etching treatment could promote the formation of sp³ bonds on the interface of substrate and DLC film. This DLC film had low friction coefficient of 0.12 and low wear rate of 5.11 × 10⁻⁷ mm³/m·N. In summary, Ti plasma etching pre-treatment could significantly improve the adhesion of DLC film and keep its excellent tribological properties.     

Bonding structure and mechanical properties of carbon nitride bilayer films with Ti and TiN interlayer

Carbon nitride (CN_x) bilayer films with Ti and TiN interlayer were synthesized by cathode arc technique at various nitrogen pressures (P_N2). The dependences of microstructure and bonding composition of the films on the P_N2 and interlayer were analyzed by Raman spectroscopy and X‐ray photoelectron spectroscopy. Microstructure evolution consisting of the ordering and size of Csp² clusters, the faction of N–sp³/N–sp² bonds and graphite‐like/pyridine‐like configurations was dominated by P_N2, interlayer and annealing. The results showed that Ti and TiN interlayer decrease the atomic ratio of N/C and increase clustering Csp². High P_N2 induces the formation of C ≡ N and C ? N bonds, the increase of sp²‐bonding content and the growth of Csp² clusters. A large part of nitrogen atoms are coordinated with sp²‐hybridized carbon (minimum 71% for annealed CN_x monolayer). TiN/CN_x bilayer had a higher content of pyridine‐like configuration. Morphological characteristics of CN_x monolayer and bilayer mainly depend on the surface character (roughness and surface energy) of the sublayer. The internal stress in the as‐deposited Ti/CN_x bilayer is smaller, but it after annealing is higher than that of CN_x monolayer and TiN/CN_x bilayer. These results may be of interest for studying the CN_x films with controlled bonding composition and expected engineering properties. Copyright © 2014 John Wiley & Sons, Ltd.     

Sputter‐deposited Ni/Ti double‐bilayer thin film and the effect of intermetallics during annealing

In the present study, a double bilayer of a Ni/Ti thin film was investigated. A nanoscale NiTi thin film is deposited in a Ni–Ti–Ni–Ti manner to form a double‐bilayer structure on a Si(100) substrate. Ni and Ti depositions were carried out by using d.c. and r.f. power, respectively, in a magnetron sputtering chamber. Four types of bilayers are formed by varying the deposition time of each layer (i.e. 15, 20, 25, and 30 min). The as‐deposited amorphous thin films were annealed at 300, 400, 500, and 600 °C for 1 h to achieve the diffusion in between the layers. Microstructures were analyzed using field‐emission scanning electron microscope and high‐resolution transmission electron microscope. It was found that, with the increase in annealing temperature from 300 to 600 °C, the diffusion at the interface and atomic migration on the surface increase. Cross‐sectional micrographs exhibited the interdiffusion between the two‐layer constituents, especially at higher temperatures, which resulted in diffusion patches along the interface. Phase analyses, performed by grazing incidence X‐ray diffraction, showed the formation of intermetallic compounds with some silicide phases that enhance the mechanical properties. Nanoindentation and atomic force microscopy were carried out to know the mechanical properties and surface profiles of the films. The surface finish is better at higher annealing temperatures. It was found that for annealing temperatures varying from 300 to 600 °C, the increase in annealing temperature resulted in a gradual increase in atomic‐cluster coarsening with improved adatom mobility. Copyright © 2016 John Wiley & Sons, Ltd.     

Evaluation of bias voltage effect on diamond‐like carbon coating properties deposited on tungsten carbide cobalt

Diamond‐like carbon (DLC) coatings are getting new trends for cutting tool applications. In this research work, the DLC coatings were deposited on 15 × 15 × 5‐mm tungsten carbide cobalt substrates with variation of bias voltage from 0 to 500 V. The DLC films of 400 nm were deposited using filter cathode vacuum arc system, and 100‐nm chromium interlayer was deposited by sputtering. The optimized conditions for plasma pretreatment at different argon flow rates and deposition rates with bias variation were found. The effect of bias voltage on microstructure, tribology, adhesion, and mechanical properties were evaluated. The characterization techniques employed were field emission electron microscopy, Raman spectroscopy, wear test, SEM, scratch test, and nano‐indentation. The effect of substrate pretreatment on film adhesion was also evaluated. It was observed that etching rate increased with the increase in Ar flow rate while DLC deposition and sputtering rates decreased with increase in the bias voltage. The characterization suggests the DLC coatings deposited at 0 V bias as optimum condition because of showing the best results among all other conditions. Copyright © 2014 John Wiley & Sons, Ltd.     

Impact of high N2 flow ratio on the chemical and morphological characteristics of sputtered N‐DLC films

Because of their outstanding characteristics, diamond‐like carbon (DLC) thin films have been recognized as interesting materials for a variety of applications. For this reason, the effects of the incorporation of different elements on their fundamental properties have been the focus of many studies. In this work, nitrogen‐incorporated DLC films were deposited on Si (100) substrates by DC magnetron sputtering of a graphite target under a variable N₂ gas flow rate in CH₄ + N₂ + Ar gas mixtures. The influence of high N₂ flow ratios (20, 40 and 60%) on the chemical, structural and morphological properties of N‐DLC films was investigated. Different techniques including field emission gun‐equipped scanning electron microscope (FEG‐SEM), energy‐dispersive X‐ray spectroscopy (EDS), atomic force microscopy (AFM), profilometry, Rutherford backscattering spectrometry (RBS) and Raman spectroscopy (325‐nm and 514‐nm excitation) were used to examine the properties of the N‐DLC films. Thus, the incorporation of nitrogen was correlated with the morphology, roughness, thickness, structure and chemical bonding of the films. Overall, the results obtained indicate that the fundamental properties of N‐DLC films are not only related to the nitrogen content in the film but also to the type of chemical bonds formed. Copyright © 2016 John Wiley & Sons, Ltd.     

Corrosion and wear resistance properties of multilayered diamond‐like carbon nanocomposite coating

Multilayered diamond‐like carbon (DLC) nanocomposite coating has been deposited on silicon and stainless steel substrates by combination of cathodic arc evaporation and magnetron sputtering. In order to make DLC coating adhered to metal substrate, a chromium interlayer has been deposited with constant bias voltage of −150 V applied to the substrate. Dense multilayered coating consists of metallic or nonmetallic and tetrahedral carbon (ta‐C) layers with total thickness of 1.44 μm. The coating has been studied for composition, morphology, surface nature, nanohardness, corrosion resistance, and tribological properties. The composition of the coating has been estimated by energy‐dispersive spectroscopy. Field‐emission scanning electron microscopy and atomic force microscopy have been used to study the surface morphology and topography. I_D/I_G ratio of ta‐C:N layer obtained from Raman spectroscopy is 1.2, indicating the disorder in the layer. X‐ray photoelectron spectroscopy studies of individual ta‐C:N, CrN, and Cr‐doped DLC layers confirm the presence of sp²C, sp³C, CrN, Cr₂N, and carbidic carbon, and sp²C, sp³C, and Cr carbide. Nanohardness studies show the maximum penetration depth of 70 to 85 nm. Average nanohardness of the multilayered DLC coating is found to be 35 ± 2.8 GPa, and Young's modulus is 270 GPa. The coating demonstrates superior corrosion resistance with better passivation behavior in 3.5% NaCl solution, and corrosion potential is observed to move towards nobler (more positive) values. A low coefficient of friction (0.11) at different loads is observed from reciprocating wear studies. Wear volume is lower at all loads on the multilayered DLC nanocomposite coating compared to the substrate.     

Self-ion irradiation on hydrogenated amorphous carbon films at depth of adhesion interlayer: Radiation-induced atomic intermixing and degraded film properties

Hydrogenated amorphous carbon (a-C:H) films consisting of a top a-C:H layer, a gradient transient a-C:H:Ti layer, and a bottom Ti layer were irradiated by 1.1-MeV C⁺ ions, resulting in a maximum displacement damage of 1.0 dpa and a projected range inside the Ti layer. Time-of-flight secondary ion mass spectrometry, electron energy loss spectroscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy analyses were performed to investigate the compositional and structural transitions of a-C:H films after self-ion irradiation. The results revealed that C⁺ ions passing through the top a-C:H layer induced C–H fracture and hydrogen diffusion in this layer and then resulted in atomic intermixing in the multilayered adhesion interlayer. After local energy deposition of C⁺ ions, the initial sharp interfaces in the a-C:H:Ti layer became ambiguous due to interfacial mixing. In addition, titanium carbides formed in the Ti layer, with a gradual phase transition from TiCx to TiC with a diffusion depth of 200 nm. The broken compositional gradients of the adhesion interlayer resulted in a significant decrease in the adhesion strength of the films, which eventually resulted in degraded antiwear properties of the irradiated film in dry sliding tribotests.     

Structural,chemical and nanomechanical investigations of SiC/polymeric a-C:H films deposited by reactive RF unbalanced magnetron sputtering

Amorphous carbon (or diamond-like carbon, DLC) films have shown a number of important properties usable for a wide range of applications for very thin coatings with low friction and good wear resistance. DLC films alloyed with (semi-)metals show some improved properties and can be deposited by various methods. Among those, the widely used magnetron sputtering of carbon targets is known to increase the number of defects in the films. Therefore, in this paper an alternative approach of depositing silicon-carbide-containing polymeric hydrogenated DLC films using unbalanced magnetron sputtering was investigated. The influence of the C₂H₂ precursor concentration in the deposition chamber on the chemical and structural properties of the deposited films was investigated by Raman spectroscopy, X-ray photoelectron spectroscopy and elastic recoil detection analysis. Roughness, mechanical properties and scratch response of the films were evaluated with the help of atomic force microscopy and nanoindentation. The Raman spectra revealed a strong correlation of the film structure with the C₂H₂ concentration during deposition. A higher C₂H₂ flow rate results in an increase in SiC content and decrease in hydrogen content in the film. This in turn increases hardness and elastic modulus and decreases the ratio H/E and H³/E². The highest scratch resistance is exhibited by the film with the highest hardness, and the film having the highest overall sp³ bond content shows the highest elastic recovery during scratching.     

The effect of interface electrostatic interaction based on acid–base theory on friction behavior

Fluorine‐containing amorphous carbon films [fluoring‐containing diamond‐like carbon (F‐DLC)] were fabricated on Si wafer by direct current plasma enhanced chemical vapor deposition (dc‐PECVD) technique using CF₄ and Ar as gas sources, confirmed by XPS and Raman analyses. The friction tests were carried out on a rotating ball‐on‐disk apparatus in high vacuum atmosphere (≤5.0 × 10^?4 Pa) at the load of 0.5 N selecting glass (mainly containing silicon–oxygen tetrahedron structure) and Al₂O₃ with the same hardness and surface roughness as the counterpart balls. The results indicate that glass/F‐DLC results in lower friction coefficient of 0.14 than that of the Al₂O₃/F‐DLC (0.20). At the same time, no wear was occurred, and the transfer layer was not formed on the counterpart ball for glass/F‐DLC, while the wear of Al₂O₃/F‐DLC is slightly larger than that of glass/F‐DLC. However, just like the glass ball, there is no formation of transfer layer on the Al₂O₃ ball surface. Furthermore, the chemical state of fluorine in the film after friction, which mainly existed in the form of the C–CF and C–F bonds, did not change compared with the F‐DLC film, while the fluorine content has changed significantly. As a result, it is assumed that interface electrostatic interaction based on acid–base theory plays an extremely important role in the process of friction. Copyright © 2017 John Wiley & Sons, Ltd.     

Electrodeposition of nanostructured diamond-like films by oxidation of lithium acetylide

Diamond-like carbon (DLC) films have been deposited by anodic oxidation of 4 M solution of lithium acetylide in dimethylsulfoxide on the surface of stainless steel or nickel electrode at room temperature and moderate anodic current densities (0.2–2.0 mA/cm²) in the range of electrode potentials 0.3–2.5 V (vs. sat. Ag|AgCl reference electrode). Electrodeposited DLC coatings represented complete and optically transparent films of a thickness 50–100 nm having dark island inclusions with a diameter 0.8–5.0 μm. The concentration and average size of these particles increased with the prolongation of deposition time. Micro-Raman spectra obtained by the focusing of laser beam onto these dark inclusions are characterized by a broad peak centered at 1500 cm⁻¹ and weak peak at 1200 cm⁻¹. With a defocused laser beam, there appear two well-distinguished peaks on the integrated Raman spectra – at 1530 and 1130 cm⁻¹. Analysis of Raman spectra with the use of a Breit–Wigner–Fano lineshape and spectrum deconvolution indicates that the electrodeposited films consist of diamond-like nanostructured carbon with a high content (70–80%) of sp³ phase.     

以Au和Au-Cu为衬底的Si/DLC薄膜的机械性能

通过纳米划痕测试技术(nano-scratch)研究了以Au和Au-Cu(xAu=93%, xCu=7%)为衬底, 多晶硅Si为基片的类金刚石(DLC)薄膜的机械性能, 其中DLC薄膜厚度约为10 nm. 研究结果表明, Au-Cu衬底对Si/DLC薄膜的结合力比Au衬底对Si/DLC薄膜的结合力要好. 紫外(244 nm)为激发光源的拉曼光谱测试结果显示在相同薄膜制备条件下Au-Cu衬底比Au衬底含有更多的sp3成分, 同时也意味着以Au-Cu为衬底的Si/DLC薄膜具有更高的硬度和密度. 通过对研究结果的分析讨论可以得出, 由于具有较好的结合力和高硬度, Au-Cu是磁记录磁头保护膜Si/DLC薄膜的更好lead材料.     

Synthesis and characterization of Ti and N binary‐doped ɑ‐C films deposited by pulse cathode arc with ionic source assistant

Using ionic source assistant, Ti and N co‐doped amorphous C (α‐C:N:Ti) thin films were prepared by pulse cathode arc technique. Microstructure, composition, elemental distribution, morphology, and mechanical properties of α‐C:N:Ti films were investigated in dependence of nitrogen source, pulse frequency, and target current by Raman spectroscopy, X‐ray diffraction, scanning electron microscopy, X‐ray photoelectron spectroscopy, atomic force microscopy, nanoindentation, and surface profilometer. The results show the presence of titanium carbide and nitride in a‐C:N:Ti films. The α‐C:N⁺:Ti film (6 Hz, 60 A) shows the smaller size and the higher disordering degree of Csp² clusters. The α‐C:N⁺:Ti films present smoother surface and smaller particle size than for α‐C:N₂:Ti films. N ions facilitate the formation of N‐sp³C bonds in the α‐C:N⁺:Ti films, and α‐C:N⁺:Ti (10 Hz, 80 A) film possesses the more graphite‐like N bonds. Higher hardness and lower residual stress present in the α‐C:N₂:Ti (10 Hz, 80 A) film.     

Effects of sputtering current on the bonding structure and mechanical properties of diamond‐like carbon films deposited by MFPUMST

Diamond‐like carbon (DLC) films on glass wafers were produced by middle frequency pulsed unbalanced magnetron sputtering technique (MFPUMST) at different sputtering current. The chemical bonding of carbon characterized by Raman spectroscopy and X‐ray photoelectron spectroscopy (XPS) show that the sp³ fraction in DLC films increases with increasing sputtering current from 100 to 300 mA, and then decreases above 300 mA. Mechanical properties like nano‐hardness and elastic recovery for these films under different sputtering currents analyzed by a nano‐indentation technique show the same tendency that nano‐hardness and elastic recovery increase with increasing sputtering current from 100 to 300 mA, and then decrease with increasing sputtering current from 300 to 400 mA. These results indicate that the sp³ fraction in the prepared DLC films is directly related to nano‐hardness and elastic recovery. The results shown above indicate that the parameter of the preparation—sputtering current has a strong influence on the bonding configuration of the deposited DLC films. The mechanism of sputtering current on the sp³ fraction is discussed in this paper. Copyright © 2009 John Wiley & Sons, Ltd.     

The properties of BCN films formed by ion beam assisted deposition

A study has been made on the formation and the properties of boron carbonnitride (BCN) thin films. The BCN films were produced by ion beam assisted deposition, in which boron and carbon were deposited by electron beam heating and nitrogen was supplied by ion implantation simultaneously. The mechanical properties of BCN films were measured using a ultra micro hardness tester and a friction tester. The atomic ratio and the structure of BCN thin films were estimated by means of X-ray photoelectron spectroscopy, laser Raman spectroscopy and Fourier transform infrared spectroscopy. As preliminary results, it was found that the BCN films are higher in hardness and lower in friction coefficient than diamond-like carbon (DLC) films. The mechanical properties are discussed with the relation of surface composition and structure.     

Enhanced electron field emission from ZnO nanoparticles-embedded DLC films prepared by electrochemical deposition

ZnO nanoparticles-embedded diamond-like amorphous (DLC) carbon films have been prepared by electrochemical deposition. Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) results confirm that the embedded ZnO nanoparticles are in the wurtzite structure with diameters of around 4 nm. Based on Raman measurements and atomic force microscope (AFM) results, it has been found that ZnO nanoparticles embedding could enhance both graphitization and surface roughness of DLC matrix. Also, the field electron emission (FEE) properties of the ZnO nanoparticles-embedded DLC film were improved by both lowering the turn-on field and increasing the current density. The enhancement of the FEE properties of the ZnO-embedded DLC film has been analyzed in the context of microstructure and chemical composition.     

Neutron reflectometry study of CrAlN/TiAlN nanostructured multilayers

Alternate CrAlN/TiAlN multilayers with different repeated bilayer thickness ranging from 10 to 20 nm were prepared by sputtering Ti, Al and Cr targets with N₂ and Ar gases. The interface structures of multilayers such as the average individual thicknesses, the scattering length densities and interface roughness were characterized using nonpolarized specular neutron reflectometry. The experimental reflectivity can be well described by a multilayer model for all samples. The individual thickness in the repeated bilayers is close to the nominal thickness. The interface roughness diminishes as the thickness of the bilayer in mutilayers decreases. The asymmetric interface roughness on CrAlN‐TiAlN‐Si interfaces causes the larger interface roughness of CrAlN on TiAlN interface. The scattering length density profiles of multilayers suggest that the chemical composition is approximate to Cr_0.86Al_0.14N/Ti_0.5Al_0.5N and which is more accurate for thinner films. Copyright © 2016 John Wiley & Sons, Ltd.     

Corrosion and tribocorrosion behaviour of super‐thick diamond‐like carbon films deposited on stainless steel in NaCl solution

Super‐thick diamond‐like carbon (DLC) film is a potential protective coating in corrosive environments. In the present work, three kinds of DLC films whose thickness and modulation periods are 4 µm and 3, 21 µm and 17 and 21 µm and 7, respectively, were fabricated on stainless steel. The effect of different thickness and modulation periods on corrosion and tribocorrosion behaviour of the DLC‐coating stainless steel was investigated in 3.5 wt% NaCl aqueous solution by a ball‐on‐flat tribometer equipped with a three‐electrode electrochemical cell. The DLC‐coating stainless steel served as a working electrode, and its OCP and potentiodynamic polarization were monitored before and during rubbing. The wear–corrosion mechanism of the DLC films was investigated by SEM. The results showed that the increasing thickness can prolong significantly lifetime of DLC films in NaCl aqueous solution. In particular, the modulation period has a significant impact on the tribocorrosion resistance of the DLC super‐thick films. The study suggested that the increasing thickness of compressive stress layer could suppress film damage by reducing crack propagation rate. Thus, the super‐thick DLC film with thickness of 21 µm and 7 periods presented the best tribocorrosion resistance among all studied films. Copyright © 2016 John Wiley & Sons, Ltd.     

Applying diamond like carbon layer on carbon/carbon composites and its effect on the deposition of hydroxyapatite coating

The biomedical application of carbon/carbon (C/C) composites is limited by lacking bioactivity and releasing carbon debris. Hydroxyapatite (HA) coating has been used to improve the bioactivity of C/C composites, but it cannot reduce the release of carbon debris effectively because of poor wear resistance property. In this work, a wear‐resistant layer of diamond like carbon (DLC) is applied on C/C composites, followed by an ultrasound‐assisted electrochemical deposition to prepare HA coatings. The microstructure, morphology and chemical composition of the DLC layer and the HA coating are characterised by scanning electron microscopy, X‐ray diffraction, energy dispersive spectroscopy (EDS), X‐ray photoelectron spectroscopy, Fourier transformed infrared spectroscopy and Raman spectrum. The bonding strength between the HA coating and the DLC layer modified C/C composites is examined by a tensile test. The results show that the DLC layer has a spherical morphology and provides a uniform surface for the deposition of the HA coating. The HA coating shows flaky morphology with a compact structure. The tensile strength of the HA coating on the DLC layer modified C/C composites is 6.24 ± 0.40 MPa, which is significantly higher than that of HA coating on unmodified C/C composites(3.04 ± 0.20 MPa). Copyright © 2013 John Wiley & Sons, Ltd.     

The high‐temperature tribological properties of Si‐DLC films

The tribological properties of Silicon‐containing diamond‐like‐carbon (Si‐DLC) films, deposited by magnetron sputtering Si target in methane/argon atmosphere, were studied in comparison with diamond‐like‐carbon (DLC) films. The DLC films disappeared because of the oxidation in the air at 500 °C, whereas the Si‐DLC films still remained, implying that the addition of Si improved significantly the thermal stability of DLC films. Retarded hydrogen release from DLC film at high temperature and silicon oxide on the surface might have contributed to lower friction coefficient of the Si‐DLC films both after annealing treatment and in situ high‐temperature environment. Copyright © 2012 John Wiley & Sons, Ltd.     

Characterisation and properties of magnetron sputtered nanoscale bi‐layered Ni/Ti thin films and effect of annealing

Single‐bi‐layer of Ni–Ti thin film was deposited using DC and RF magnetron sputtering technique by layer‐wise deposition of Ni and Ti on Si(100) substrate in the order of Ni as the bottom layer and Ti as the top layer. The deposition of these amorphous as‐deposited thin films was followed by annealing at 300 °C, 400 °C, 500 °C, and 600 °C temperature with 1‐h annealing time for each to achieve crystalline thin films. This paper describes the fabrication processes and the novel characterization techniques of the as‐deposited as well as the annealed thin films. Microstructures were analysed using FESEM and HRTEM. Nano‐indentation and AFM were carried out to characterize the mechanical properties and surface profiles of the films. It was found that, for the annealing temperatures of 300 °C to 600 °C, the increase in annealing temperature resulted in gradual increase in atomic‐cluster coarsening with improved ad‐atom mobility. Phase analyses, performed by GIXRD, showed the development of silicide phases and intermetallic compounds. Cross‐sectional micrographs exhibited the inter‐diffusion between the two‐layer constituents, especially at higher temperatures, which resulted either in amorphization or in crystallization after annealing at temperatures above 400 °C. Copyright © 2015 John Wiley & Sons, Ltd.