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20 pages, 12353 KiB

Open AccessArticle

Improving Mechanical and Tribological Behaviors of GLC Films on NBR under Water Lubrication by Doping Ti and N

by Zhen Zhou, Yanfeng Han and Jin Qian

Coatings 2022, 12(7), 937; https://doi.org/10.3390/coatings12070937 - 1 Jul 2022

Cited by 4 | Viewed by 1479

Abstract

Water lubrication has been widely used in marine equipment, where rubber bearings and seals suffer intense friction and severe wear under mixed and boundary conditions. It has good research prospects and practical value to study the composite of amorphous carbon on water lubrication [...] Read more.

Water lubrication has been widely used in marine equipment, where rubber bearings and seals suffer intense friction and severe wear under mixed and boundary conditions. It has good research prospects and practical value to study the composite of amorphous carbon on water lubrication rubber to improve lubrication and reduce wear. In this work, modified graphite-like carbon films incorporated with titanium and nitrogen ((Ti:N)-GLC) were integrated on nitrile butadiene rubber (NBR) with multi-target magnetron sputtering. Direct current (DC) sputtering of graphite target was used as the carbon source. The incorporation of Ti and N elements was accomplished by using radio frequency (RF) magnetron sputtering of three different targets: Ti, TiC and TiN, to optimize the mechanical and tribological performance. This work is aimed to clarify the modification mechanism of Ti and N incorporation and obtain the optimum scheme. The influence of RF power on surface topography, chemical composition, mechanical properties and tribological properties was investigated by SEM, XPS, Raman spectra, nanoindentor and tribometer. The consequences revealed that the characteristics of films depend on RF target types and power. For the Ti-C and TiC-C series, when RF power is 100 W and below, with low content of Ti (6 at.%~13 at.%) and N (around 10 at.%), the incorporation of Ti and N optimizes the surface topology, improves the mechanical properties and maintains excellent adhesion to NBR substrate. The tribological and wear behaviors of (Ti:N)-GLC films are better than GLC films under mixed and boundary lubrication. When RF power grows to 200 W, the dopants result in the deterioration of surface and mechanical properties, followed by worse lubrication and wear behaviors. For TiN-C series, the incorporation of TiN takes no advantage over GLC films, even worse in the case of high RF power. Overall, the incorporation of Ti or TiC by magnetron sputtering in Ar/N2 atmosphere is an effective modification method for GLC films on NBR to improve mechanical and tribological behaviors. Full article

(This article belongs to the Special Issue Tribology and Mechanical Behavior of Amorphous Carbon Coatings)

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25 pages, 5817 KiB

Open AccessArticle

Friction Response of Piston Rings for Application-like Starvation and Benefit of Amorphous Carbon Coatings

by Björn Michelberger, Dirk Jaitner, Andreas Hagel, Patrick Striemann, Benjamin Kröger, Franz-Josef Wetzel, Andreas Leson and Andrés Fabián Lasagni

Coatings 2022, 12(6), 738; https://doi.org/10.3390/coatings12060738 - 27 May 2022

Cited by 4 | Viewed by 2321

Abstract

The oil supply at the interface between the top ring and the cylinder liner (TRCL) plays a major role in an internal combustion engines efficiency. In particular, the interface forms a trade-off between the serving of enough lubricant for sufficient lubrication conditions and [...] Read more.

The oil supply at the interface between the top ring and the cylinder liner (TRCL) plays a major role in an internal combustion engines efficiency. In particular, the interface forms a trade-off between the serving of enough lubricant for sufficient lubrication conditions and emissions through subsequent combustion. This can lead to deficient top ring lubrication conditions. In this study, a new developed reciprocating long-stroke tribometer, enabling the variation of oil supply, is used to investigate such application-like starved lubrication conditions of the TRCL interface. With the simulative investigations, a comparison with the fired engine is possible. The performance of diamond-like carbon coatings is compared to standard nitrided piston rings. It was found that the tetrahedral amorphous carbon (ta-C) coatings exhibit up to 31% reduced friction as well as a lower wear under starved lubrication conditions. Simulative investigations show a good correlation between engine friction and tribometer measurements for selected oil supply conditions. Full article

(This article belongs to the Special Issue Tribology and Mechanical Behavior of Amorphous Carbon Coatings)

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19 pages, 6163 KiB

Open AccessArticle

Wear Study of a Magnetron-Sputtered TiC/a-C Nanocomposite Coating under Media-Lubricated Oscillating Sliding Conditions

by Johannes Schneider, Sven Ulrich, Jörg Patscheider and Michael Stueber

Coatings 2022, 12(4), 446; https://doi.org/10.3390/coatings12040446 - 25 Mar 2022

Cited by 6 | Viewed by 1992

Abstract

Friction and wear performance of non-reactively magnetron-sputtered hydrogen-free TiC/a-C coatings were characterized under lubricated oscillating sliding conditions against 100Cr6 steel. The friction mediators, isooctane, ethanol and distilled water, were chosen to address the actual trend of environmentally friendly green technologies in mobility and [...] Read more.

Friction and wear performance of non-reactively magnetron-sputtered hydrogen-free TiC/a-C coatings were characterized under lubricated oscillating sliding conditions against 100Cr6 steel. The friction mediators, isooctane, ethanol and distilled water, were chosen to address the actual trend of environmentally friendly green technologies in mobility and the potential use of carbon-based nanocomposite thin film materials for tribocomponents in contact with gasoline and alternative biofuels. Sliding pairs of the TiC/a-C coatings showed significantly reduced friction and wear compared to the reference materials under both unlubricated and lubricated conditions (when using the aforementioned media isooctane, ethanol and distilled water). Quasi-stationary friction coefficient of the TiC/a-C sliding pairs after running-in was almost independent of test conditions and could be traced back to self-lubrication as a result of the formation of a transfer layer on the steel counter body. Wear of the coatings based on micro-abrasion and tribochemical reaction was significantly influenced by the environmental conditions. Lowest wear was measured after tests in non-polar isooctane whereas highest wear was measured after tests in water. Full article

(This article belongs to the Special Issue Tribology and Mechanical Behavior of Amorphous Carbon Coatings)

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13 pages, 2198 KiB

Open AccessArticle

Amorphous Carbon Coatings with Different Metal and Nonmetal Dopants: Influence of Cathode Modification on Laser-Arc Evaporation and Film Deposition

by Tim Krülle, Frank Kaulfuß, Volker Weihnacht, Falko Hofmann and Florian Kirsten

Coatings 2022, 12(2), 188; https://doi.org/10.3390/coatings12020188 - 1 Feb 2022

Cited by 6 | Viewed by 2322

Abstract

In this study, the arc evaporation of pure graphite and composite cathodes with small amounts of metals (Mo, Fe) or nonmetals (B, Si) was investigated by means of a laser-arc process. Both specific aspects of the arc evaporation and the effects on the [...] Read more.

In this study, the arc evaporation of pure graphite and composite cathodes with small amounts of metals (Mo, Fe) or nonmetals (B, Si) was investigated by means of a laser-arc process. Both specific aspects of the arc evaporation and the effects on the deposition of the doped and undoped carbon coatings were studied. The deposition rate, the chemical composition and the mechanical properties of the generated films were evaluated. In addition, the dependence of the deposition rate and the composition on the height position of the substrates in relation to the cathode were also the subject of the investigations. Finally, the erosion rate and the arc spot behavior on the cathode were analyzed. It is shown that homogeneously doped (t)a-C:X coatings can be reliably synthesized with the laser-arc technique. There are differences in the various properties of the coatings and the deposition rate. The latter is attributed in particular to the erosion behavior of the cathodes. Full article

(This article belongs to the Special Issue Tribology and Mechanical Behavior of Amorphous Carbon Coatings)

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15 pages, 3632 KiB

Open AccessArticle

Superlow Friction of a-C:H Coatings in Vacuum: Passivation Regimes and Structural Characterization of the Sliding Interfaces

by Takuya Kuwahara, Yun Long, Maria-Isabel De Barros Bouchet, Jean Michel Martin, Gianpietro Moras and Michael Moseler

Coatings 2021, 11(9), 1069; https://doi.org/10.3390/coatings11091069 - 4 Sep 2021

Cited by 16 | Viewed by 2656

Abstract

A combination of atomistic simulations and vacuum tribometry allows atomic-scale insights into the chemical structure of superlubricious hydrogenated diamond-like carbon (a-C:H) interfaces in vacuum. Quantum molecular dynamics shearing simulations provide a structure-property map of the friction regimes that characterize the dry sliding of [...] Read more.

A combination of atomistic simulations and vacuum tribometry allows atomic-scale insights into the chemical structure of superlubricious hydrogenated diamond-like carbon (a-C:H) interfaces in vacuum. Quantum molecular dynamics shearing simulations provide a structure-property map of the friction regimes that characterize the dry sliding of a-C:H. Shear stresses and structural properties at the sliding interfaces are crucially determined by the hydrogen content

C_{H}

in the shear zone of the a-C:H coating. Extremely small

C_{H}

(below 3 at.%) cause cold welding, mechanical mixing and high friction. At intermediate

C_{H}

(ranging approximately from 3 to 20 at.%), cold welding in combination with mechanical mixing remains the dominant sliding mode, but some a-C:H samples undergo aromatization, resulting in a superlubricious sliding interface. A further increase in

C_{H}

(above 20 at.%) prevents cold welding completely and changes the superlubricity mechanism from aromatic to hydrogen passivation. The hydrogen-passivated surfaces are composed of short hydrocarbon chains hinting at a tribo-induced oligomerization reaction. In the absence of cold welding, friction strongly correlates with nanoscale roughness, measured by the overlap of colliding protrusions at the sliding interface. Finally, the atomistic friction map is related to reciprocating friction experiments in ultrahigh vacuum. Accompanying X-ray photoelectron and Auger electron spectroscopy (XPS, XAES) analyses elucidate structural changes during vacuum sliding of a hydrogen-rich a-C:H with 36 at.% hydrogen. Initially, the a-C:H is covered by a nanometer-thick hydrogen-depleted surface layer. After a short running-in phase that results in hydrogen accumulation, superlubricity is established. XPS and XAES indicate a non-aromatic 1–2-nm-thick surface layer with polyethylene-like composition in agreement with our simulations. Full article

(This article belongs to the Special Issue Tribology and Mechanical Behavior of Amorphous Carbon Coatings)

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15 pages, 10112 KiB

Open AccessArticle

Excellent Seizure and Friction Properties Achieved with a Combination of an a-C:H:Si DLC-Coated Journal and an Aluminum Alloy Plain Bearing

by Takumi Iwata, Masakuni Oikawa, Riki Chida, Daijiro Ishii, Hidemi Ogihara, Yuji Mihara and Makoto Kano

Coatings 2021, 11(9), 1055; https://doi.org/10.3390/coatings11091055 - 31 Aug 2021

Cited by 13 | Viewed by 2185

Abstract

Friction occurring between the crank journal and main bearings accounts for a large share of the mechanical losses of automotive engines. The effects of higher in-cylinder pressures and narrower bearings have raised the specific load applied to bearings, making it essential to secure [...] Read more.

Friction occurring between the crank journal and main bearings accounts for a large share of the mechanical losses of automotive engines. The effects of higher in-cylinder pressures and narrower bearings have raised the specific load applied to bearings, making it essential to secure sufficient seizure resistance as well. For the purpose of meeting both requirements, we have endeavored to reduce friction and improve seizure resistance by applying a diamond-like carbon (DLC) coating to the crank journal. In the present study, a bearing tester was used that has received international standard certification from the International Organization for Standardization for reproducing the sliding behavior occurring between the crank journal and main bearings in actual engines. Test results indicated that a silicon-containing hydrogenated amorphous carbon (a-C:H:Si) DLC-coated journal showed a definite friction reduction and a marked improvement in seizure resistance. An acoustic emission (AE) analysis revealed that an adhesion-induced AE peak observed for a steel journal was not seen for the DLC-coated journal. Additionally, tin and aluminum elements in the bearing material that were transferred to and observed on the sliding surface of the steel journal were not seen on the DLC-coated journal. Accordingly, the low affinity of the DLC coating with these metal elements presumably led to the clear friction reduction and superior seizure resistance displayed by the DLC coating. Full article

(This article belongs to the Special Issue Tribology and Mechanical Behavior of Amorphous Carbon Coatings)

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16 pages, 10556 KiB

Open AccessArticle

Tribological Properties of a Mesh-Like Nanostructured Diamond-Like Carbon (DLC) Lubricated with a Fully Formulated Oil at DLC/Steel Contacts under Boundary Lubrication

by Hikaru Okubo, Seiya Watanabe, Shinya Sasaki, Yuuki Tokuta, Hideki Moriguchi, Daisuke Iba and Ichiro Moriwaki

Coatings 2021, 11(7), 746; https://doi.org/10.3390/coatings11070746 - 22 Jun 2021

Cited by 3 | Viewed by 2391

Abstract

The present paper describes the tribological properties of a mesh-like nanostructure of diamond-like carbon (DLC) in a formulated engine oil at DLC/steel contacts. This novel nanostructured DLC was characterized as a non-hydrogenated amorphous carbon (a-C) with a nano-mesh structure layer at the outermost [...] Read more.

The present paper describes the tribological properties of a mesh-like nanostructure of diamond-like carbon (DLC) in a formulated engine oil at DLC/steel contacts. This novel nanostructured DLC was characterized as a non-hydrogenated amorphous carbon (a-C) with a nano-mesh structure layer at the outermost surface, herein named NM-a-C. From the results of our friction tests, we observed that the NM-a-C/steel tribopair exhibited lower friction and higher wear-resistance than the a-C:H/steel tribopair, though the mechanical properties were nearly identical. The analytical result indicated that the tribofilm formation process and the chemical composition of the tribofilm varied depending on the types of the DLC. In particular, thicker MoS₂-rich tribofilms formed on the NM-a-C surface. Hence, the NM-a-C structure promoted the formation of MoS₂ under the lubrication with the fully formulated oil, leading to lower friction and high wear-resistance at the DLC/steel contact under boundary lubrication conditions. Full article

(This article belongs to the Special Issue Tribology and Mechanical Behavior of Amorphous Carbon Coatings)

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15 pages, 6454 KiB

Open AccessArticle

Boride-Carbon Hybrid Technology for Ultra-Wear and Corrosive Conditions

by Nina Baule, Young S. Kim, André T. Zeuner, Lars Haubold, Robert Kühne, Osman L. Eryilmaz, Ali Erdemir, Zhong Hu, Martina Zimmermann, Thomas Schuelke and Qi-Hua Fan

Coatings 2021, 11(4), 475; https://doi.org/10.3390/coatings11040475 - 18 Apr 2021

Cited by 3 | Viewed by 2479

Abstract

This work discusses a study on a surface treatment for creating extremely durable low-friction, wear and corrosion-resistant surfaces for tribological components in harsh conditions. A duplex surface treatment was developed that combines the advantages of ultra-fast electrochemical boriding with those of hard tetrahedral [...] Read more.

This work discusses a study on a surface treatment for creating extremely durable low-friction, wear and corrosion-resistant surfaces for tribological components in harsh conditions. A duplex surface treatment was developed that combines the advantages of ultra-fast electrochemical boriding with those of hard tetrahedral amorphous carbon coatings. The friction and wear properties of the duplex treatment are compared to the boride-only treatment of AISI 1045 steel, while corrosion and contact fatigue behaviors of the duplex layer are compared to that of the single-layer carbon coating on low carbon steel. The duplex treatment yields wear rates as low as 6 × 10⁻⁸ mm³·N⁻¹·m⁻¹ and a coefficient of friction of 0.14 when tested against a steel counter face. The contact fatigue impact tests reveal that the high hardness of 1200 HV0.05 of the borided layer in the duplex treatment leads to higher resistance against indentation but is accompanied by a higher incidence of crack initiation, being in good agreement with the finite-element modeling of nanoindentation results. The duplex coatings exhibit resistance to pinhole corrosion as evidenced by a 3 h exposure to 15% HCl at room temperature. Full article

(This article belongs to the Special Issue Tribology and Mechanical Behavior of Amorphous Carbon Coatings)

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Review

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33 pages, 9769 KiB

Open AccessFeature PaperReview

Structure and Characterization of Vacuum Arc Deposited Carbon Films—A Critical Overview

by Bernd Schultrich

Coatings 2022, 12(2), 109; https://doi.org/10.3390/coatings12020109 - 18 Jan 2022

Cited by 8 | Viewed by 1897

Abstract

This critical overview analyzes the relations between deposition conditions and structure for hydrogen-free carbon films, prepared by vacuum arc deposition. The manifold of film structures can be roughly divided into graphitic, nanostructured and amorphous films. Their detailed characterization uses advantageously sp³ fraction, [...] Read more.

This critical overview analyzes the relations between deposition conditions and structure for hydrogen-free carbon films, prepared by vacuum arc deposition. The manifold of film structures can be roughly divided into graphitic, nanostructured and amorphous films. Their detailed characterization uses advantageously sp³ fraction, density, Raman peak ratio and the mechanical properties (Young’s modulus and hardness). Vacuum arc deposition is based on energetic beams of carbon ions, where the film growth is mainly determined by ion energy and surface temperature. Both parameters can be clearly defined in the case of energy-selected carbon ion deposition, which thus represents a suitable reference method. In the case of vacuum arc deposition, the relation of the external controllable parameters (especially bias voltage and bulk temperature) with the internal growth conditions is more complex, e.g., due to the broad energy distribution, due to the varying “natural” ion energy and due to the surface heating by the ion bombardment. Nevertheless, some general trends of the structural development can be extracted. They are critically discussed and summarized in a hypothetical structural phase diagram in the energy-temperature plane. Full article

(This article belongs to the Special Issue Tribology and Mechanical Behavior of Amorphous Carbon Coatings)

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