DLC coatings are widely used for their protective properties such as high wear resistance, low friction coefficient as well as chemical inertness. However, their electrical resistance is usually very ...high, which limits their utilization in electrotechnical applications. To improve electrical conductivity, DLC films are typically doped with nitrogen or metals. This study, however, investigates the mechanical and electrical properties of un-doped, hydrogenated DLC films deposited using temperatures above 450 °C. To further enhance the coating's properties, hydrogen gas was added during deposition.
The DLC coatings were produced by means of PA-CVD using a pulsed DC discharge. Temperatures of 450 °C, 500 °C and 550 °C were used to deposit a-C:H films on steel substrate. The process gas consisted of a mixture of argon and acetylene. Additionally, coatings were deposited with hydrogen added to the gas mixture. A silicon-based interlayer served as an electrical insulator between substrate and coating and was deposited with HMDSO as a precursor. To measure the specific electrical resistivity of the films, the van der Pauw method was performed. The mechanical properties of the coatings were determined through nanoindentation. Raman spectroscopy was performed to analyze the structure of the DLC coatings.
The films showed a significant decrease in specific electrical resistivity with increasing deposition temperature. Values dropped to <104 μΩ cm at 550 °C, attaining levels close to graphite. Hardness and Young's modulus increased up to 147 % with rising deposition temperature. The addition of 18 % hydrogen gas during deposition resulted in at least 60 % further reduction in specific electrical resistivity, while also slightly raising coating hardness for deposition temperatures above 450 °C. With this new distinct deposition method, electrically conductive a-C:H coatings with improved mechanical properties can be produced only by increasing the deposition temperature and the utilization of hydrogen as process gas.
•Deposition of thick, electrically conductive a-C:H coatings with PACVD•The a-C:H coatings improved in mechanical and electrical properties.•Increase in deposition temperature led to graphitization and lower hydrogen content.•Addition of hydrogen gas to the process gas mixture lowered hydrogen content of DLC.•Undoped DLC with high film thickness and promising electrical properties
In the present study, the main critical factors affecting the production of high tribological performance coatings on substrates containing near surface graphite were evaluated. Plasma nitriding ...followed by deposition of a hydrogenated diamond like carbon film (a-C:H) on gray cast iron (GCI) and nodular cast iron (NCI) substrates were carried out using a single thermal cycle. The surface topography evolution was evaluated via Scanning Electron Microscopy (SEM) and White Light Interferometry (WLI). As expected, there is a huge variation in surface topography and morphology according to graphite shape. An intense modification on the topography of GCI was observed, in particular wedges formation after nitriding. In order to enable a more in-depth understanding, the surface evolution after plasma nitriding of cast irons was carefully investigated and discussed in light of EDS linescans and XRD. Micro Raman spectroscopy and TEM analysis indicated that the DLC has an average amount of clustered sp2 bonding in the structure. Additionally, the tribological performance of multifunctional coatings was evaluated via durability tests in ambient air, which revealed friction coefficients as low as 0.06 during steady-state lubrication regime for gray cast iron substrates, whereas the values were of 0.14 for nodular cast iron substrates. Crucial differences were found between friction coefficient behaviours: the GCI presented lubricious tribolayers covering most part of wear track whereas NCI presented topographic factors inhibiting tribolayers formation, a key factor that might explain the friction coefficient variation.
•DLC (a-C:H) deposited in cast irons by pulsed DC PECVD presented average amount of sp2 clusters.•Improved explanation for the radical topography increase after the nitriding of gray cast irons•Coated gray cast irons presented COF of 0.06 during lubricious regime in dry sliding reciprocating tests.
In this work, Diamond Like Carbon (DLC) thin films were deposited on aluminum alloy 6061 by Plasma-Assisted Chemical Vapor Deposition (PACVD). Nitiding prior to coated leads to appropriate hardness ...gradient and it can greatly improve the mechanical properties of the coatings. The composition, crystalline structure and phase of the films were investigated by Grazing Incidence X-ray Diffraction (GIXRD). Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) were employed to observe the morphology and structure of the film. The DLC layer exhibited a columnar structure. The adhesion force between the film and the aluminum alloy 6061 was 30.8 Mpa. The DLC film was determined by the pull of test. The hardness of the DLC film was 12.75 Gpa. The improvement of the adhesion DLC was attributed to a less gradient hardness configuration. In addition, the mean friction coefficient of the films was about 0.2 determined by nanoindentation test. According to the results, the high and unique hardness of this coating leads to increase of the wear resistance and thus the useful life of parts.
Diamond like Carbon (DLC) was deposited on aluminum substrate using Plasma Assisted Chemical Vapor Deposition (PACVD) route. Spattering, the surface was activated before deposition for increasing ...adhesion. Deposition time was varied from 60 minutes to 5 hours. Deposit was characterized using with grazing incidence X-ray diffraction and atomic force microscope. The mechanical property was measured using microhardness and roughness tester. The analysis showed that the deposit consisted of columnar growth of submicron and micron meter scale. Compared to substrate material, deposit showed higher hardness and roughness. These results show that growth of DLC layer includes three stages. The first stage is primary growth of nuclei, and then these nuclei join together in second stage. In third stage, secondary growth of these nuclei happens.
Surface modification is widely adopted as a viable solution for surface damage under sliding or impacting conditions. Various coatings can be manufactured using different techniques and it has been ...applied on various substrates in previous studies which results in different characteristics. This review presents the anti-wear techniques with a focus on the most recent coatings of superior properties. Hard protective coatings may consist of various compositions; however, based on the hardness and the resistance to wear, some of the frequently used elements are Titanium (Ti), Nickel (Ni), carbides, Zirconium (Zr), Boron (B) and the Diamond Like Carbon (DLC). The deposition methods such as Chemical Vapor Deposition (CVD), Physical Vapor Deposition (PVD) as well as the cutting-edge coating hybrid-deposition methods such as Pulsed DC Magnetron Sputtering (PDCMS), High Power impulse (HiPIMS) and Arc Ion Plating (AIP) are reviewed and the resulted significant differences in the coating properties are discussed. In this review, listing the most important findings from previous studies in a table for each group of coatings make it easy to compare between various techniques and coatings. Some of the listed factors affecting the coating properties, such as the substrate, and others affecting the coefficient of friction, such as the counter body, were not been sufficiently highlighted before despite their importance in analyzing the tribological behavior for the coatings investigated. Although the focus was on the most recent studies, a wide range of studies was covered in order to accumulate and integrate the knowledge toward a complete analysis and discussion. Coating hardness is essential for better wear resistance; however, coating bonding, thickness and roughness may be equally important. Various techniques are used to improve the bonding. For some coatings, the Coefficient of Friction (CoF) increases with increasing the wear resistance where the counter body plays a major role. For most of the deposition techniques, the controlling parameters are the cleaning treatment, arc current, pressure, time, and gas supply. It was found that diamond-like carbon coatings are among the hardest coatings and the Plasma-Assisted Chemical Vapor Deposition (PACVD) is frequently reported as one of the most promising deposition techniques. Many coatings including the diamond-like carbon coating were not been investigated for their erosion wear resistance by solid particles despite the importance of such investigations for many applications.
•Coatings based on Titanium, Nickel, carbides, Zirconium, Boron and the Diamond Like Carbon are discussed and compared.•Coating properties according to deposition technique such as CVD, PVD, and Pulsed DC Magnetron Sputtering are discussed.•Coatings properties, testing conditions, deposition techniques and other parameters are listed in comparative tables.•Coating hardness is important but coating-substrate adhesion controlled by deposition techniques may be more significant.•Plasma-Assisted Chemical Vapor Deposition is frequently reported as one of the most promising deposition techniques. There is a limited number, and sometimes a lack, of solid particles erosion studies for the recently developed coatings.
TiBCN coating is known as a hard, self-lubricant and wear resistant coating which can be applied on industrial tools to increase their working life time under severe wear conditions. In this paper, ...TiBCN coatings with different B/C ratios were applied on H13 steel using plasma-assisted chemical vapor deposition from BBr3, TiCl4, CH4, N2 and H2 reactants at 500 °C. The results signified that the introduction of B and C elements to TiN changed its preferred crystalline orientation from (200) to (111) and decreased crystal size from 12 to 9 nm as a result of the formation of amorphous phases which constrain grain growth. The addition of B and C altered the coating's nucleation and growth mechanisms and generated a strong surface etching agent of HBr which significantly changed surface morphology and roughness. Increasing flow ratio of CH4 to BBr3 from 0.125 to 0.25 influenced the coating's mechanical properties and increased coating's hardness from 18.1 to 23.2 GPa and Young's modulus from 296 to 334.7 GPa. Rising coating's C content remarkably improved its nano-wear resistance and the coating with the highest C content exhibited a wear volume of 1*10−19 m3 which was about 63% lower than that of TiN coating.
In this study, titanium aluminium carbonitride (TiAlCN) ceramic coatings with different precursors' ratio of AlCl3/TiCl4 were deposited on H13 hot work tool steel substrates, using pulsed-DC plasma ...assisted chemical vapor deposition method. The coatings showed a nanocomposite microstructure consisted of fcc-TiAlN and hcp-AlN nanocrystalline grains and an amorphous carbon phase. Increasing the precursors' ratio from 0.5 to 3 led to an increase in Al content from ∼10 to ∼42 at.%. Moreover, with increasing the precursors' ratio, the surface roughness of the coating reduced initially from 21.39 to 14.44 nm, due to the creation of more nuclei of AlN and then it rose up to 18.26 nm. Coating with the precursors' ratio of 0.5 presented the highest microhardness of 3840 HV0.01,due to the less amount of chloride impurity and hcp-AlN phase. The precursors’ ratio of 0.5 resulted in the highest wear resistance and lowest coefficient of friction of around 0.17.
This work presents results of investigations of electronic properties of undoped boron nitride (BN) films produced on Si substrates in the course of radio frequency (rf) PACVD process with boron ...triethyl (C2H5)3B as the boron source. The influence of the deposition process parameters on thickness and electronic properties (resistivity r, dielectric strength EBR) of BN films based on ellipsometry and I-V curve measurements at room temperature is studied. The obtained results show that proper selection of deposition process parameters allows BN layers with the required thickness and advantageous values of r and EBR to be fabricated. BN becomes therefore an interesting material for microelectronics applications.
Surface damage by solid particles impacting at high speed is a significant problem for many applications. Hardening and coating are widely adopted to improve surface resistance. The Diamond-Like ...Carbon (DLC) coating is produced by highly advanced methods that make it one of the hardest coatings with improved bonding to the substrate. In this study, the Solid Particles Erosion (SPE) resistance of the DLC coating deposited by Plasma Assisted Chemical Vapor Deposition (PACVD) on hardened stainless steel grade 410 (SS 410H) was investigated. The results were compared to the SS 410H and SS 410 without hardening. The ASTM G 76 gas blast tester was used to find the SPE resistance, represented by Erosion Rate (ER), under velocities of (30, 50, 70) meter per second and angles of (30, 45, 60, 70, 90) degrees. The results were used to provide the constants needed for a modified Sheldon-Kanher (SK) ER model to estimate the ER at any velocity and impact angle for the tested materials, most importantly, for the DLC coating. A ductile erosion behavior was observed for the tested materials where the ER is reduced by increasing the impact angle which proves that the DLC coating does not behave as a brittle material under SPE. The DLC coating showed the highest SPE resistance with improvement of 42–65% with almost no significant effect of the velocity and impact angle on the improvement rate. While the SS 410H showed an improvement of 6–44% with a significant fluctuation with the variation of velocities and angles. This study highlights the potential usage of DLC coating in mechanical parts exposed to solid particles, such as turbine/compressor blades.
•Hard coating is one of the effective methods against Solid Particle Erosion (SPE).•Diamond Like Carbon (DLC) coating is one of the most promising coating with superior tribological properties.•DLC coating deposited by Plasma Assisted Chemical Vapor Deposition (PACVD) technique was investigated.•The SPE resistance for stainless steel grade 410 hardened and coated with DLC coating was investigated.•Sheldon-Kanher erosion model was modified to identify the constants needed to estimate the erosion rate for the DLC coating.
The conventional DC-pulsed PACVD method was applied to deposit DLC and N-DLC coatings on AISI H13 substrate. ased on the optimized parameters achieved for single layer, N-DLC/DLC double layer ...coatings were deposited using two different techniques, namely: conventional and active screen. Chemical bindings and structural evolutions of double-layer coatings were investigated by visible Raman spectroscopy, and X-ray Photoelectron Spectroscopy (XPS). Accordingly, the friction coefficient of the active screen N-DLC/DLC coating at the end of the wear test was obtained about the value of 0.12 which was found to be the lowest among all samples.
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