DLC Coatings Research Articles

Understanding the role of tungsten species in diamond-like carbon coatings for enhanced interaction with ionic liquids

This study investigated the impact of tungsten species in tungsten-doped diamond-like carbon (WDLC) coatings on their interactions with ionic liquids (ILs). Using analytical techniques such as in-situ neutron reflectometry, time-of-flight secondary ion mass spectrometry, and Raman spectroscopy, we examined the adsorption mechanism of tributylmethylphosphonium dimethylphosphate on WDLC and undoped hydrogenated DLC (hDLC) coatings. These techniques provide high-resolution insights into the molecular interactions, revealing that tungsten doping enhances the formation of tungsten carbide and tungsten oxides. These species facilitate the dissociation of dimethylphosphate anions, forming a robust 0.75 nm-thick tungsten phosphate layer on the WDLC surfaces. This layer, which adheres strongly even after cleaning, underscores the role of tungsten in enhancing the effectiveness and lubrication properties of WDLC coatings with ILs.

Effect of Water on Wear of DLC Coatings in High Temperature and Pressurized Ethanol

The friction and wear characteristics of a-C:H:Si and a-C:H coatings in an ethanol environment at 120 °C and 10 MPa focusing on the effects of water and dissolved oxygen in ethanol were investigated. The friction tests were conducted using an autoclave chamber, with gases (oxygen or nitrogen) and ethanol–water mixtures (0 and 6 vol.%). The wear acceleration of a-C:H:Si took place when it slid in ethanol with 6 vol.% water and pressurized by oxygen, thus the specific wear rate was the highest, approximately 1.8 × 10−7 mm3/Nm. The reason of this wear acceleration was assumed the effect of hardness reduction due to oxidation of the a-C:H:Si, so the O/C ratio by AES and the hardness of topmost surface by AFM nano-scratch were investigated. As a result, the higher O/C ratio showed higher specific wear rate due to the hardness reduction from 13.3 to 6.0 GPa. These findings highlight the role of water and dissolved oxygen in accelerating wear of a-C:H:Si coatings.Graphical abstract

Superlubricity of multilayer titanium doped DLC coatings by using low SAPS organic additives in base oil

This study systematically investigates the tribological performance of titanium doped diamond-like carbon monolayer and multilayer coatings with superior mechanical properties. The coatings were lubricated in poly alpha olefin grade 4 (PAO4) base oil, containing three concentrations of two organic, ashless, and sulfur free (low SAPS) antiwear, and extreme pressure additives with different amounts of phosphorus and nitrogen (Duraphos® 178 and Duraphos® OAP). The multilayer Ti-doped DLC coatings exhibited superior tribological performance compared to uncoated steel, undoped DLC, and monolayer Ti-DLC coatings. They exhibited coefficient of friction values which were in the range of 0.013 and 0.006 (superlubricity) for formulations with Duraphos® OAP. Duraphos® 178 significantly lowered the specific wear rates of both the monolayer and multilayer coatings.

Enhanced corrosion resistance of a novel periodic multilayered Si/(Si, N)-DLC coating against simulated coal mine water

In this study, a novel periodic multilayered DLC coating, which was composed of a Si interlayer and a Si/N co-incorporated DLC layer (Si/(Si, N)-DLC) per period, was deposited; the corrosion behavior under the neutral, acidic, or alkaline coal mine water environment and its periodic number dependence, especially the fundamental corrosion mechanism, were systemically explored. Results suggest that compare to the substrate, the introduction of multilayered Si/(Si, N)-DLC coating presents a dramatic enhancement in the corrosion resistance under coal mine water environment. However, with increasing the periodic number, the corrosion resistance of the multilayered coating strongly depends on the working environment, which exhibits an enhancement in neutral and alkaline environments while a degeneration in acidic environment. This is attributed to not only the prolongation of the corrosion path caused by the multilayered structure but also the formation of an insulating silicon oxide layer in neutral and alkaline environments. However, in acidic environments, the strong permeability of H+ with the smallest ionic radius easily infiltrates the inherent defects of the coating. This not only weakens the protective properties of the multilayer structure but also leads to hydrogen-induced cracking, ultimately diminishing corrosion resistance. These findings theoretically guide the development of the DLC coatings with excellent corrosion resistance for coal mine applications.

Effect of compound surface modification of shot peening and DLC coating on surface integrity and fatigue properties of gear steel 16Cr3NiWMoVNbE

We conducted a study on the surface compound modification of shot peening and pure carbon DLC coating to simultaneously meet the requirements of wear resistance and fatigue resistance of spline structure. The effects of surface compound modification were investigated on the surface morphology, residual stress profile, microstructure, and nano-indentation hardness of 16Cr3NiWMovNbE gear steel, and conducted a comparative study on fatigue performance. The results show that the surface compound modification inherits the surface morphology and compressive residual stress gradient of shot peening, while the surface residual stress is slightly smaller than that of shot peening. In addition, surface compound modification still reflects the characteristics of high hardness and high fracture resistance of DLC coatings. Under the bending load based on spline tooth root, compared to the original specimen, the fatigue life after shot peening, pure carbon DLC coating, and surface compound modification is increased by 3.68, 2.35, and 3.36 respectively. Although the compound modified surface still maintains the shot peening morphology with a increasing surface roughness and stress concentration coefficient, the 100 μm-depth compressive residual stress profile and the subgrain refinement layer introduced, as well as the hard surface layer with good load-bearing capacity, have played the role of fatigue strengthening.

Effects of CrC interlayer on tribocorrosion properties of DLC-coated TC4 alloy in a 0.9 wt% NaCl solution

In this study, DLC coatings with varying thicknesses of CrC interlayers were fabricated on the surface of TC4 alloy by regulating the flow rate of C2H2. The effects of the interlayer layer on the microstructure, mechanical properties, corrosion resistance, and tribocorrosion resistance of DLC coatings were systematically investigated. The results show that as the C2H2 flow rate increases, the CrC interlayer exhibits the structure transitions from columnar crystals to amorphous, resulting in improved hardness. The hardness of the CrC40 interlayer reaches 17.2 GPa, significantly higher than the 9.3 GPa of the Cr underlayer. The CrC interlayer notably enhances the mechanical properties and adhesion strength of DLC coatings. The corrosion current density of the CrC40/DLC coating is 3.07 × 10−8 A/cm2, significantly lower than that of the DLC coating with only a Cr underlayer. Under high load conditions of 20 N, the tribocorrosion rate of the CrC40/DLC coating is reduced to 2.09 × 10−7 mm3.(N.m)−1, representing a significant decrease of 93.9 % compared to the DLC coating. The CrC40/DLC coating exhibits strong adhesion strength, appropriate internal stress and a relatively hard CrC40 interlayer, showing exceptional tribocorrosion resistance.

Precision depth-controlled isolated silver nanoparticle-doped diamond-like carbon coatings with enhanced ion release, biocompatibility, and mechanical performance

Silver doped diamond-like carbon (Ag/DLC) coatings are in high demand for biomedical applications such as artificial implants, surgical instruments, and medical devices. However, recent reports indicate that the excess Ag concentration required in typically made Ag/DLC coatings significantly reduces their mechanical performance and biocompatibility. Here, we propose a novel single-step approach to precisely dope small quantities of Ag in the form of isolated nanoparticles embedded at defined depths in a DLC matrix. This new Ag/DLC coating architecture is designed to release controlled Ag ion levels to fight infection in the early post-surgery stages, while a confined Ag amount maintains the excellent mechanical and biocompatibility performance of the underlying DLC coating when compared to typically made Ag/DLC coating designs. Coatings of pure DLC, typically made Ag/DLC with Ag doped throughout the carbon matrix and the new Ag/DLC design with precise Ag doping, are made using a modified magnetron sputtering system. The coatings are characterised for structural, mechanical, ion leaching, and biocompatibility profiles against L929 fibroblast cells. Results indicate that the new Ag/DLC coating requires only 2 at.% Ag to release a similar level of Ag ions (∼0.6 ppm) to a typical Ag/DLC coating with a much higher Ag content of 17 at.%. The new Ag/DLC coating design also outperforms the typical design with a 63 % increase in hardness, 100 % higher Young's modulus, and 21 % higher biocompatibility. The enhanced biomechanical performance of the proposed new Ag/DLC architecture could have significant potential for coating of future medical devices.

The Evaluation of the Cytotoxicity and Corrosion Processes of Porous Structures Manufactured Using Binder Jetting Technology from Stainless Steel 316L with Diamond-like Carbon Coating

With the growing interest in additive manufacturing technology, assessing the biocompatibility of manufactured elements for medical and veterinary applications has become crucial. This study aimed to investigate the corrosion properties and cytotoxicity of porous structures designed to enhance the osseointegration potential of implant surfaces. The structures were fabricated using BJ technology from 316L stainless steel powder, and their surfaces were modified with a DLC coating. The studies carried out on porous metal samples with and without DLC coatings demonstrated low cytotoxicity. However, no significant differences were found between the uncoated and DLC-coated samples, likely due to variations in the thickness of the coating on the porous samples and the occurrence of mechanical damage.

Study on preparation and anti-sand erosion performance of thick DLC coating combined with FCVA deposition and HVP technology

To address the compatibility issues between the hardness and thickness of DLC coatings and to improve the erosion resistance of engine blades, a thick DLC coating was prepared using a combination of filter cathode vacuum arc (FCVA) deposition technology and high voltage pulse (HVP) technology. The prepared thick DLC coating exhibits low residual stress (1.79 ± 0.087 GPa) and high C-sp3 content (70.13 %), with a thickness and hardness of 18.46 μm and 51.07 ± 0.23 GPa, respectively. The results of anti-sand erosion tests indicate that the mass loss rates of DLC coating at the erosion angles of 45° and 90° are 4.44 × 10−3 mg/g and 1.99 × 10−2 mg/g, respectively. The good erosion resistance of thick DLC coatings is attributed to the consumption of residual impact energy by carbon cluster structures, which prevents the generation and propagation of cracks. Therefore, the thick and super-hard DLC coatings can be prepared by combining FCVA deposition technique with HVP technique, which has great potential applications in the aerospace industry.

Nitrogen-Stabilized DLC Coatings: Optimization of Properties and Deposition Parameters Using Randomized Tree and Neural Network Algorithms

Nitrogen-Stabilized DLC Coatings: Optimization of Properties and Deposition Parameters Using Randomized Tree and Neural Network Algorithms

In-situ Wear Detection of DLC Coatings under Application-oriented Conditions

In-situ Wear Detection of DLC Coatings under Application-oriented Conditions

Сравнение трибологических свойств алмазоподобного покрытия в паре со сталью / керамикой при сухом трении и граничной смазке

. Studies conducted in the last decade having proven experience of many years of practical use in friction units of various mechanisms and machines used in the national economy, have shown that the effective way to ensure their longevity, reliability and energy conservation is to apply DLC coatings on the friction surfaces of contacting parts in these friction nodes. It has now been established that the effectiveness of the use of these coatings is determined to a large extent by the conditions of their operation and the materials of the contacting parts. In the presented article, friction pairs are compared in terms of anti-friction properties, in which the studied steel samples with an amorphous DLC coating applied to steel through an intermediate layer of titanium aluminitride wear out under conditions of dry friction and film lubrication. Standard balls made of bearing chromium alloyed steel and ceramics based on silicon nitride are used as a wearing coupled element. Tribological experiments are carried out on the well-known laboratory installation KT-2 with an upgraded friction unit, which allows for the contact of a wearing ball with three horizontally positioned rollers, on the cylindrical surfaces of which the coating under study is applied. The article provides an analysis of the results of these experiments. In addition to DLC coating tests, data on tests of uncoated and coated samples with only a layer of titanium aluminitride are provided for comparison. A harder coupled element material can significantly affect the tribological properties, destroying coatings, thereby reducing the positive effects of the antifriction properties of coatings, and even lead to increased wear due to the formed abrasive particles in the friction zone.

Impacts of DLC and Cr-DLC coatings on noise level emitted during contact fatigue tests on AISI 4320 steel carburized gears

Impacts of DLC and Cr-DLC coatings on noise level emitted during contact fatigue tests on AISI 4320 steel carburized gears

Evaluation of the effects of the application of Ti−C:H DLC coatings obtained by PVD techniques in the kinematic pairs of internal combustion engines and powertrain systems.

The article attempts to analyze the possible effects of using Ti−C:H DLC carbon coatings produced by pulsed magnetron sputtering (PVD) to reduce friction coefficient and wear in kinematic pairs found in internal combustion engines and powertrain systems used in automotive vehicles. The aim of such action is primarily to reduce internal losses in the aforementioned units. The coatings were deposited on heat-treated bearing steel 100Cr6, examined using a scanning electron microscope FEI Quanta 200 Mark II with the chemical analyzer EDS EDAX Genesis XM 2i, tribotester T−01M examining the friction coefficient in the ball-disc correlation and Hommel Werke T8000 profilometers, additionally, in order to check the coating thickness, studies were carried out using the Calotest method. The results obtained indicate that both the friction coefficient and wear are drastically reduced in relation to samples on which no DLC coatings were applied.

Micropitting performance and friction behaviour of DLC coated bearing steel surfaces : On the influence of Glycerol-based lubricants

A better understanding about the rolling contact fatigue and micropitting performance of machine component surfaces lubricated with environmentally friendly lubricants is critical to designing and further formulating new lubricants intended to be used in rolling–sliding contacts such as those found in gear and bearing applications. In this work, the frictional behaviour and rolling contact fatigue (RCF) performance of DLC, Cr/a-WC:H/a-C:H and a-C:Cr coatings under glycerol-based lubrication in rolling sliding contact conditions have been investigated. Traction maps, Stribeck curves, and fatigue plots have been generated by using a micropitting test rig (MPR). The initiation and progression of micropitting was monitored by means of white light optical interferometry and scanning electron microscopy (SEM). Results indicated that glycerol-based lubricants exhibited a significant friction reduction as the hydrodynamic effect is enhanced at higher rolling-speeds. Under boundary lubrication the friction coefficient was significantly higher compared to the values obtained with a commercial mineral-based transmission oil. Compared to uncoated steel surfaces, DLC coatings effectively reduced the volume loss and micropitting progression. Irrespective of the coating thickness, DLC showed an excellent tribological behaviour when the base lubricant favours the onset of mild-wear, over micropitting. When the lubricant formulation favoured the onset of micropitting, the coatings tended to prematurely fail due to debonding from the substrate, and local micro-spallation. The experiments demonstrated that friction reduction does not necessarily correspond with a reduction of micropitting.

Highly radiation-stable DLC coatings for a new class of detectors: Structural and morphological features

Within the framework of the FTM-NEXT INFN (Fast Time Micropattern gaseous detectors - next of Nuclear Physics National Institute) experiment, we produced hydrogen-free diamond-like carbon films through pulsed-laser deposition to serve as resistive layers in modern resistive micro-pattern gaseous detectors that must work in extreme radiation environments at future colliders. To obtain homogeneous diamond-like carbon coatings, over medium-to-large size (3 cm × 3 cm), with excellent adhesion to the substrate and with typical surface resistivity values in the range of 1–100 MOhm/sq, growth conditions had to be optimized. In this paper we report on the stability of resistive diamond-like carbon layers subjected to increasing doses of irradiation with proton beams accelerated to an energy of 2 MeV. The morphological, structural, and electrical properties, also at the nanoscale level, of diamond-like carbon coatings following ion irradiation were studied by electron microscopy, electron diffraction, electrical transport characterization and scanning tunneling spectroscopy.

Effect of Hybrid Surface Treatment Composed of Plasma Nitriding and DLC Coating on Friction-Wear Properties and Fatigue Strength of Alloy Tool Steel SKD11

Effect of Hybrid Surface Treatment Composed of Plasma Nitriding and DLC Coating on Friction-Wear Properties and Fatigue Strength of Alloy Tool Steel SKD11

ADAPTIVE DLC COATINGS WITH DIFFERENT MoS2 CONTENT

DLC coatings are widely used in engineering as they are resistant to abrasive wear. However, they exhibit anincreased coefficient of friction at temperatures of around 300C. Soft MoS2 coatings are known to maintaina low coefficient of friction at temperatures up to about 350C, but suffer from relatively high abrasive wear.Publications from the last decade report a synergistic improvement in the tribological performance of acoating consisting of both these materials. The aim of this study was to investigate the wear resistance ofcoatings composed of different a-C and MoS2 contents applied by magnetron sputtering on steel. The resultsobtained in tribological tests conducted using the ball-and-disk method showed at least 20% better adhesionto the substrate of the two-component nanocomposite coating and its increased wear resistance from 15% toas much as 700%, compared to single-component coatings in tests conducted at 20C and 250C. The testsshowed no deterioration of the two-component coating's coefficient value compared to DLC.

New nanoscale multilayer magnetron sputtered Ti-DLC/DLC coatings with improved mechanical properties

Two sets of nanoscale multilayer Ti-DLC/DLC coatings, with similar chemical composition but different periods between consecutive layers (0.4 and 5.5 nm), were deposited by non-reactive direct current magnetron sputtering using different rotational speeds of the substrate holder (12 and 1 rpm, respectively) in this work. The results show that the overall Ti content in the coatings varied from ≈ 2.9 to ≈ 8.2 at. % in both cases. Significant fluctuations in the Ti concentration between the middle points of the DLC and Ti-DLC layers were observed for the coatings deposited at 1 rpm. All the coatings deposited were mainly amorphous, presenting a columnar structure and a cauliflower-like granular surface morphology. The sp2/sp3 ratio increased as the concentration of Ti rose. The coatings deposited at 1 rpm demonstrated better mechanical properties (up to 33 % improvement in hardness and up to 25 % improvement in the elastic modulus) when compared to the equivalent coatings deposited at 12 rpm. The multilayer titanium doped coating (deposited at 1 rpm) with 5.9 at. % Ti presented the most significant improvement in mechanical properties when compared to pure DLC and monolayer coatings deposited at 12 rpm. The results confirmed that it is possible to tune the performance of this type of coatings by depositing alternating layers of pure DLC and Ti-doped DLC.

Tribological behavior of DLC film models in base oils: Analysis of influence of sp3/sp2 ratio and hydrogen content

DLC coatings have been proven in formulated oils used in the automotive industry. The development of electric cars and its consequences on the future of the internal combustion engine makes it increasingly necessary that these coatings take their place in other applications where lubrication is generally of lower quality such as for example strips cold rolling where DLC shows significant potential both for production and finishing cold rolling. As a result, the interest of the behavior of these coatings in base oils takes on a new dimension. In this study, we explore the influence of the composition and the sp3/sp2 ratio on tribological behavior of DLC coatings in mineral and synthetic base oils. Hydrogenated DLC films deposited by conventional PECVD with various levels of hydrogen measured by Elastic Recoil Detection Analysis (ERDA) and non-hydrogenated DLC films deposited by PLD in the nanosecond mode (ns-PLD) and by cathodic arc evaporation, thus allowing to have different sp3/sp2 ratios confirmed by Multiwavelength Raman spectrometry, are tested and compared. The tests are performed on a ball-on-flat device with coated balls to better evaluate wear level. The behavior of highly hydrogenated DLC is of particular interest; with a very high level of durability in both base oils and friction level which comparatively varies between low and very low depending on the base oil.