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Lubricants
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Friction and Wear of Coatings/Films
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Friction and Wear of Coatings/Films

A special issue of Lubricants (ISSN 2075-4442).

Deadline for manuscript submissions: closed (31 March 2023) | Viewed by 25239

Special Issue Editors

Dr. Shusheng Xu

E-Mail Website
Guest Editor
State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China
Interests: tribology; friction; wear; solid lubrication; PVD coatings/films; self-lubricating materials
Special Issues, Collections and Topics in MDPI journals
Dr. Liuquan Yang

E-Mail Website
Guest Editor
Institute of Functional Surfaces, School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, UK
Interests: surface engineering; thin film deposition; tribology in demanding environment
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In the 21st century, energy and material losses due to friction and wear in moving mechanical systems have accounted for huge economic and environmental burdens all over the world. A significant amount of fuel is spent in overcoming friction in moving mechanical machine parts, and if energy losses and emission figures due to the remanufacturing and replacement of worn parts are also taken into consideration, the energy and environmental impacts become proportionally much greater. Therefore, the ability to control friction and wear has become a top priority worldwide. Numerous new lubricant oils, lubricious bulk materials and coatings/films have been discovered and applied in practice to minimize the adverse impacts of friction and maximize the positive impacts of saving materials on all moving machine components. Among the many friction and wear control technologies, advanced solid coatings/films on the surface of moving component are becoming an attractive choice, as liquid lubricants and bulk materials are incompatible in special operating conditions. The coated components can be more energy efficient due to a reduction in frictional and wear loss. Overall, to meet the harsher operational conditions of modern machines, the current industrial trend is focusing on the increased use of advanced coatings/films to more effectively reduce friction and wear in all types of moving mechanical systems as their price decreases and quality increases.

In this Special Issue, we would like to include a collection of research and review papers concerning the field of cutting-edge discoveries in low-friction and high wear-resistant coatings/films and the friction control and wear protection of coatings/films on moving mechanical components subjected to tribological requirements.

We appreciate your consideration and hope you will accept our invitation to present your novel work.

Dr. Shusheng Xu
Dr. Liuquan Yang
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Lubricants is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • coatings/films
  • lubricants
  • tribology
  • friction
  • wear
  • boundary lubrication
  • experiments and simulations

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Published Papers (15 papers)

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Research

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15 pages, 7713 KiB  
Article
Tribological Response of δ-Bi2O3 Coatings Deposited by RF Magnetron Sputtering
by Sandra E. Rodil, Osmary Depablos-Rivera and Juan Carlos Sánchez-López
Lubricants 2023, 11(5), 207; https://doi.org/10.3390/lubricants11050207 - 07 May 2023
Cited by 2 | Viewed by 1217
Abstract
Bismuth oxide (Bi2O3) coatings and composite coatings containing this oxide have been studied due to their potential applications in gas sensing, optoelectronics, photocatalysis, and even tribology. Two parametric models based on chemical features have been proposed with the aim [...] Read more.
Bismuth oxide (Bi2O3) coatings and composite coatings containing this oxide have been studied due to their potential applications in gas sensing, optoelectronics, photocatalysis, and even tribology. Two parametric models based on chemical features have been proposed with the aim of predicting the lubricity response of oxides. However, such models predict contradictory values of the coefficient of friction (COF) for Bi2O3. In this study, we deposited Bi2O3 coatings, via magnetron sputtering, on AISI D2 steel substrates to evaluate the tribological responses of the coatings and determine which parametric model describes them better. Experimentally, only coatings presenting the cubic defective fluorite-like δ-Bi2O3 phase could be evaluated. We performed pin-on-disk tests at room temperature and progressively increasing temperatures up to 300 °C using alumina and steel counter-bodies. Low wear and COFs (0.05 to 0.15) indicated that the δ-phase behaves as a lubricious solid, favoring the validity of one of the models. An alternative explanation is proposed for the low COF of the defective fluorite-like structure since it is well known that it contains 25% of anionic vacancies that can be ordered to form low shear-strength planes, similar to the Magnéli phases. Two challenges for future potential applications were observed: one was the low adhesion strength to the substrate, and the other was the thermal stability of this phase. Full article
(This article belongs to the Special Issue Friction and Wear of Coatings/Films)
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16 pages, 6107 KiB  
Article
Synthesis, Wear and Corrosion of Novel Electrospark and Electrospark–Electrochemical Hybrid Coatings Based on Carbon Steels
by Iurii Benkovsky, Natalia Tsyntsaru, Serhii Silkin, Vladimir Petrenko, Vidas Pakstas, Henrikas Cesiulis and Alexandr Dikusar
Lubricants 2023, 11(5), 205; https://doi.org/10.3390/lubricants11050205 - 05 May 2023
Cited by 1 | Viewed by 1009
Abstract
The electrospark deposition (ESD) technique is a low-heat-input process that has great potential for coating applications and the restoration of damaged high-value parts. Carbon steels are commonly used as a substrate material for ESD coatings. However, we demonstrated that carbon steels could be [...] Read more.
The electrospark deposition (ESD) technique is a low-heat-input process that has great potential for coating applications and the restoration of damaged high-value parts. Carbon steels are commonly used as a substrate material for ESD coatings. However, we demonstrated that carbon steels could be used successfully as the electrode tool for the ESD process. Furthermore, ESD coatings commonly have a high as–deposited roughness. In view of this, in order to reduce the roughness of the ESD coatings, electrodeposition as a tool to alter surface morphology was investigated. Hence, the micro-leveling power of several electrolytes for Ni, Fe-W, Fe, and Cr electrodeposition were evaluated. The maximum leveling effect was detected for Ni electroplated from the Watts electrolyte. Thus, the novel hybrid coatings based on an ESD layer and a subsequent layer of electrodeposited Ni were obtained. ESD layers were obtained by using the following electrode tools as anodes: several types of carbon steels (St20, St30, and St45), alloys T15K6 (WC + TiC + Co), CuNiZn; and NiCr. The morphology and structure of the obtained hybrid coatings with an electrodeposited Ni top-layer was analyzed and compared to ESD coatings from the point of view of their wear and corrosion behavior. The wear rate of the novel ESD coatings based on carbon steels was comparable with coatings obtained using the NiCr electrode tool. Moreover, for all the studied cases, the corrosion resistance of the hybrid coatings was higher than for their ESD counterparts and close to electrolytic chromium. Full article
(This article belongs to the Special Issue Friction and Wear of Coatings/Films)
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19 pages, 9628 KiB  
Article
Effect of Substrate Roughness and Contact Scale on the Tribological Performance of MoS2 Coatings
by Chen Wang, Jianjun Zhang, Kai Le, Yuqi Niu, Xiaoming Gao, Qinglun Che, Shusheng Xu, Yuzhen Liu and Weimin Liu
Lubricants 2023, 11(5), 191; https://doi.org/10.3390/lubricants11050191 - 27 Apr 2023
Cited by 3 | Viewed by 1769
Abstract
This present study aimed to clarify the effect of contact scale and surface topography of substrates with different roughnesses on the actual contact area, tangential stiffness, and tangential deformation of the substrate at micro- and macro-scales via finite element method (FEM) simulations, as [...] Read more.
This present study aimed to clarify the effect of contact scale and surface topography of substrates with different roughnesses on the actual contact area, tangential stiffness, and tangential deformation of the substrate at micro- and macro-scales via finite element method (FEM) simulations, as well as the final tribological performances of MoS2 coatings by experiments. The MoS2 coatings were deposited on stainless steel (SS) substrates with different roughnesses, and the settings in the simulation models were based on the roughness of the SS substrates. The predicted tribological behavior of the simulation results was confirmed by the morphological and compositional analysis of the wear track using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), 3D profilometer, and Raman spectroscopy. The results showed that the substrate with a surface roughness of Ra 600 nm (R600), coated by MoS2 nanosheets, exhibited excellent tribological properties at both micro- and macro-scales. At the micro-scale, the lubrication lifetime of R600 was as long as 930 cycles, while the substrates with surface roughnesses of Ra 60 nm (R60) and Ra 6 nm (R6) had a lubrication lifetime of 290 cycles and 47 cycles, respectively. At the macro-scale, the lifetime of the substrate R600 was 9509 cycles, which was nearly six times longer than the 1616 cycles of substrate R60. For the rough surface of substrate, the surface grooves could not only effectively preserve the lubricant but also continuously release them, ensuring that the lubricants with low shear strength were always present in the contact interface. It was further verified that the high surface roughness of the substrate reduced friction and wear by reducing the actual contact area and enhancing the tangential stiffness of asperities, thereby prolonging the lubrication lifetime. The wear mechanisms were discussed in terms of the morphology and chemical composition of the wear tracks. Full article
(This article belongs to the Special Issue Friction and Wear of Coatings/Films)
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17 pages, 5740 KiB  
Article
Spreading Behavior of Single Oil Droplet Impacting Surface with/without a Thin Liquid Film
by He Liang, Peiyi Yang, Wenzhong Wang, Yanfei Liu, Xiangyu Ge and Baohong Tong
Lubricants 2023, 11(1), 31; https://doi.org/10.3390/lubricants11010031 - 12 Jan 2023
Cited by 3 | Viewed by 1412
Abstract
When oil droplets impact a solid surface for oil-air lubrication, they may spread out to produce a thin oil layer on the surface, which serves as a significant source of lubrication. A test rig was constructed in this research to observe the spreading [...] Read more.
When oil droplets impact a solid surface for oil-air lubrication, they may spread out to produce a thin oil layer on the surface, which serves as a significant source of lubrication. A test rig was constructed in this research to observe the spreading behavior of oil droplets impacting surfaces from both frontal and lateral views. From the frontal view, laser-induced fluorescence techniques are used to measure the thickness of the oil layer quantitatively during the spreading of oil droplets. While the lateral view can observe the shape evolution of the droplets. Oil droplet spreading patterns on the sheet with dry surfaces and with different thin liquid film thicknesses were studied, and the effect of viscosity and the thickness of the thin liquid film on spreading radius and spreading thickness is considered. The experimental findings demonstrate that the maximum spreading factor, the spreading central layer thickness, and the apparentness of retraction all increase as viscosity increases. The retraction is obviously impacted by thin liquid films, and the retraction weakens as the thin liquid film thickness increases. Full article
(This article belongs to the Special Issue Friction and Wear of Coatings/Films)
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19 pages, 9213 KiB  
Article
Thermal Fatigue Resistance Studies of Multilayer CrN and AlTiN Coatings Deposited on Plasma Nitrided H-13 Hot Work Steel
by Chetan Gurada, Rajesh Mundotia, Umesh Mhatre, Ashwin Kale and Dushyant Kothari
Lubricants 2023, 11(1), 19; https://doi.org/10.3390/lubricants11010019 - 05 Jan 2023
Viewed by 1255
Abstract
H-13 steel surface was duplex-treated using Plasma Nitriding (PN) and PVD coatings to solve the thermal fatigue problem faced in die-casting applications. Chromium-based multilayer CrN/Cr (m-CrN) coatings and multi-component aluminium–titanium-based AlTiN (m-AlTiN) coatings were deposited using a cathodic arc deposition technique after plasma [...] Read more.
H-13 steel surface was duplex-treated using Plasma Nitriding (PN) and PVD coatings to solve the thermal fatigue problem faced in die-casting applications. Chromium-based multilayer CrN/Cr (m-CrN) coatings and multi-component aluminium–titanium-based AlTiN (m-AlTiN) coatings were deposited using a cathodic arc deposition technique after plasma nitriding the H-13 steel surface with different case-depths of 50 µm and 200 µm. The structural, tribological, corrosion, and mechanical properties of the duplex-treated samples were studied. The thermal fatigue (TF) test was conducted by heating the sample to 600 °C and rapidly cooling it to room temperature, simulating the die-casting process conditions. After multiple cycles, it was observed that the oxide layer thickness formed was lower on duplex-treated samples compared to that on the uncoated plasma nitride sample. In addition, the mechanical properties were improved with the increase in PN diffusion depth. The duplex-treated samples showed better mechanical and thermal fatigue properties compared to untreated and only coated samples. The sample with m-AlTiN deposited on plasma nitrided H-13 with 200 µm case depth displays better thermal fatigue properties compared to the other samples. Full article
(This article belongs to the Special Issue Friction and Wear of Coatings/Films)
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19 pages, 6749 KiB  
Article
Influence of Deposition Temperature on the Structure and Current-Carrying Friction Performance of Cu Films by DC Magnetron Sputtering Technology
by Hao Zhang, Kai Le, Chen Wang, Jianbo Sun, Shusheng Xu and Weimin Liu
Lubricants 2023, 11(1), 8; https://doi.org/10.3390/lubricants11010008 - 26 Dec 2022
Cited by 3 | Viewed by 1670
Abstract
The structure and morphology of Cu films deposited by DC magnetron sputtering on silicon and stainless-steel substrates at different deposition temperatures of −140 °C, −95 °C, −55 °C, 25 °C (RT), 50 °C, and 200 °C were investigated by X-ray diffraction (XRD), scanning [...] Read more.
The structure and morphology of Cu films deposited by DC magnetron sputtering on silicon and stainless-steel substrates at different deposition temperatures of −140 °C, −95 °C, −55 °C, 25 °C (RT), 50 °C, and 200 °C were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). It was found that all Cu films presented strong orientation of the (111) and (200) peaks. The Cu films deposited at low temperatures (lower than −55 °C) showed the bilayer structures, in which the upper layer appeared to be a loose and porous structure and the lower layer near the substrate had a fine and dense structure that consisted of small grains. In addition, the Cu films deposited at low temperatures could be observed a large roughness. The roughness tended to decline and then increase with the rising of deposition temperature. The ball-on-disc reciprocating sliding tribometer was employed to evaluate the tribological behaviors of the Cu films at current-carrying levels of 0 A, 0.5 A, and 1.0 A. The results revealed that the Cu films deposited at low temperatures exhibited outstanding current-carrying friction performance and low electrical contact resistance (ECR), peeling only at 0.5 A and 1.0 A. Nevertheless, the Cu films deposited at the relatively high temperature exhibited oxidative wear caused by electric arc ablation at 0.5 A and 1.0 A. Additionally, the wear mechanism was discussed in terms of the structure and morphology of the wear track and formation of the tribo-film. Full article
(This article belongs to the Special Issue Friction and Wear of Coatings/Films)
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14 pages, 4304 KiB  
Article
Deformation Behavior of Crystalline Cr–Ni Multilayer Coatings by Using Molecular Dynamics Simulation
by Kuk-Jin Seo and Dae-Eun Kim
Lubricants 2022, 10(12), 357; https://doi.org/10.3390/lubricants10120357 - 09 Dec 2022
Cited by 1 | Viewed by 1130
Abstract
This work shows the atomic scale deformation behavior of crystalline multilayer coating comprising up to five Cr and Ni layers. A molecular dynamics simulation was conducted to visualize the atomic scale behavior of the multilayer during indentation/unloading and scratch. Normal and shear directional [...] Read more.
This work shows the atomic scale deformation behavior of crystalline multilayer coating comprising up to five Cr and Ni layers. A molecular dynamics simulation was conducted to visualize the atomic scale behavior of the multilayer during indentation/unloading and scratch. Normal and shear directional forces were recorded to compare repulsion and friction forces between the multilayer models during the indentation/unloading and scratch simulations. Dislocation lines within the layers were quantified to understand the deformation behavior of each model. Atomic scale deformation and dislocation lines after the indentation and scratch were visualized. Generation and movement of a single dislocation line during the indentation simulation were also visualized within a few picoseconds. The repulsion and friction forces of the five-layer model showed the lowest values among the models. The unloading stiffness of the five-layer model was calculated to be the lowest among the models. The amount of plastic deformation and the wear volume of the one-layer model after the indentation and scratch was calculated to be the highest among the models. The number of dislocation lines of the five-layer model showed an increasing trend during the indentation and scratch. The highest dislocation density of the five-layer model might aid in an enhancement of resistance to the plastic deformation to reduce the wear volume when scratched. Full article
(This article belongs to the Special Issue Friction and Wear of Coatings/Films)
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16 pages, 6240 KiB  
Article
The Verification of Engine Analysis Model Accuracy by Measuring Oil Film Pressure in the Main Bearings of a Motorcycle High-Speed Engine Using a Thin-Film Sensor
by Takumi Iwata, Masakuni Oikawa, Michiyasu Owashi, Yuji Mihara, Keisuke Ito, Yoshinari Ninomiya, Yohei Kato and Shinya Kubota
Lubricants 2022, 10(11), 314; https://doi.org/10.3390/lubricants10110314 - 18 Nov 2022
Cited by 2 | Viewed by 1324
Abstract
To improve the accuracy of the calculation analysis of crank journal bearings in motorcycle engines and accurately understand lubrication conditions, the oil film conditions of actual crankshafts and journal bearings should be measured. This research study focuses on the oil film pressure generated [...] Read more.
To improve the accuracy of the calculation analysis of crank journal bearings in motorcycle engines and accurately understand lubrication conditions, the oil film conditions of actual crankshafts and journal bearings should be measured. This research study focuses on the oil film pressure generated in the main bearing, and by using an original thin-film pressure sensor with improved durability achieved through the use of DLC (Diamond-like Carbon), it was possible to perform experiments at a maximum of 13,000 rpm and full load, which was not possible before. This established a method for measuring the oil film pressure generated in the main bearing of a high-speed motorcycle engine during operation without changing the surrounding environment. The maximum oil film pressure was 140 MPa, and the oil film pressure generated by each main bearing was successfully measured under different experimental conditions. The timing of pressure onset agreed well between the calculation and experiment stages, but the peak oil film pressure values were different. By varying the temperature of the engine in the calculation model, the calculated values approached the measured values. In the future, we plan to investigate ways to improve the accuracy of the current analytical model. Full article
(This article belongs to the Special Issue Friction and Wear of Coatings/Films)
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12 pages, 4710 KiB  
Article
Measurement of Piston Pin-Bore Oil Film Pressure under Engine Operation
by Takumi Iwata, Michiyasu Owashi, Masakuni Oikawa, Yuji Mihara, Kunihiko Kobayashi and Naoki Yamakawa
Lubricants 2022, 10(10), 258; https://doi.org/10.3390/lubricants10100258 - 13 Oct 2022
Cited by 3 | Viewed by 2022
Abstract
Thin-film sensors were used to measure the oil film pressure distribution at the piston pin-bore interface in order to ascertain the stress distribution on the piston pin of a gasoline engine during actual operation. Thin-film sensors have been manufactured by a sputtering method [...] Read more.
Thin-film sensors were used to measure the oil film pressure distribution at the piston pin-bore interface in order to ascertain the stress distribution on the piston pin of a gasoline engine during actual operation. Thin-film sensors have been manufactured by a sputtering method to a total film thickness of about 3–6 μm. The features of thin-film sensors have been utilized to successfully measure the oil film pressure on engine main bearings, connecting rod bearings and piston skirts of both diesel and gasoline automotive engines. However, as engine lubrication conditions have become more severe year by year, it has become necessary to develop thin-film pressure sensors with higher durability. The use of diamond-like carbon (DLC) coating for the protective film of the thin-film sensor has enabled accurate measurement of oil film pressure under engine operating conditions. The AVL EXCITETM Power Unit was used in simulations with the application of elastic fluid lubrication theory. The calculated values were compared with measured data, and a comparison was made of the effect of the model constraint condition. Full article
(This article belongs to the Special Issue Friction and Wear of Coatings/Films)
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15 pages, 3101 KiB  
Article
Potential of Nitrided and PVD-MoS2:Ti-Coated Duplex System for Dry-Running Friction Contacts
by Bastian Lenz, Stefanie Hoja, Michaela Sommer, Henning Hasselbruch, Andreas Mehner and Matthias Steinbacher
Lubricants 2022, 10(10), 229; https://doi.org/10.3390/lubricants10100229 - 20 Sep 2022
Cited by 4 | Viewed by 1328
Abstract
Self-lubricating coatings can be used to increase the service life of machine parts which are subjected to high mechanical loads. The present work is concerned with the combination of nitriding and a subsequent Ti-doped MoS2 coating. The focus of the investigations is [...] Read more.
Self-lubricating coatings can be used to increase the service life of machine parts which are subjected to high mechanical loads. The present work is concerned with the combination of nitriding and a subsequent Ti-doped MoS2 coating. The focus of the investigations is on the impact of the compound layer on the wear behavior of the coating since the changes in the surface topography due to compound layer growth and pore formation inside the compound layers are expected to have an impact of the adhesion strength and the wear behavior. For this purpose, compound layers with varying thickness and porosity were formed in the surface area of the material EN31CrMoV9 by gas nitriding. A MoS2:Ti PVD monolayer was applied directly on the compound layers. The wear behavior was evaluated using the pin-on-disc test. The MoS2:Ti solid lubricant coatings show good adhesion on the compound layers without any interlayer. Compared with the nitrided reference state, the coating significantly improved the wear behavior of the surface treated material. Full article
(This article belongs to the Special Issue Friction and Wear of Coatings/Films)
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13 pages, 6218 KiB  
Article
Wear Properties of C-MoS2-PTFE Composite Coating Prepared on 4032 Aluminum Alloy
by Xuehui Chen, Yuxi Zhang, Congmin Li, Lei Huang, Yu Wang, Ting Gao, Zhenbin Zhang and Wei Liu
Lubricants 2022, 10(8), 181; https://doi.org/10.3390/lubricants10080181 - 10 Aug 2022
Cited by 5 | Viewed by 1843
Abstract
A large number of joint friction pairs work during the work of scroll compressors, resulting in high energy consumption and short service life of scroll compressors. To improve the tribological performance of friction pairs of the scroll compressors, the C-MoS2-PTFE (Polytetrafluoroethylene) [...] Read more.
A large number of joint friction pairs work during the work of scroll compressors, resulting in high energy consumption and short service life of scroll compressors. To improve the tribological performance of friction pairs of the scroll compressors, the C-MoS2-PTFE (Polytetrafluoroethylene) lubrication coating is prepared through spraying technology on the surface of 4032 aluminum alloy, a common material for scroll compressors. The microstructure of the C-MoS2-PTFE coating was analyzed by X-ray diffractometer (XRD) and scanning electron microscope (SEM), and the wear behavior of the coating under different loads was studied by reciprocating friction and wear testing machine and three-dimensional profiler. The surface of the grinding marks was analyzed by SEM and energy density spectrum (EDS). The performance was compared with the anodized film of 4032 aluminum alloy and the Ni-coated coating of 4032 aluminum alloy. The experimental results show that the C-MoS2-PTFE coating has a dense structure, and the hardness is 35 HV0.1. Under dry friction conditions, the C-MoS2-PTFE coating has excellent wear reduction and wear resistance, and the coefficient of friction and wears rate under different loads are less than those of the anodized film of 4032 aluminum alloy and the Ni-plated coating. The wear mechanisms of C-MoS2-PTFE coating are fatigue wear, adhesive wear, abrasive wear, and oxidation wear under different loads. Full article
(This article belongs to the Special Issue Friction and Wear of Coatings/Films)
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12 pages, 3385 KiB  
Article
Improvement of Mechanical Properties and Adhesion of Ti-Al-Si-N Coatings by Alloying with Ta
by Artur R. Shugurov, Evgenii D. Kuzminov, Yuriy A. Garanin, Alexey V. Panin and Andrey I. Dmitriev
Lubricants 2022, 10(8), 178; https://doi.org/10.3390/lubricants10080178 - 07 Aug 2022
Cited by 1 | Viewed by 1485
Abstract
The effect of the Ta content on the structure, mechanical properties and adhesion of magnetron-sputtered Ti1-x-y-zAlxTaySizN coatings was studied. According to the energy-dispersive X-ray spectroscopy analysis, the coatings studied had the following chemical compositions: Ti [...] Read more.
The effect of the Ta content on the structure, mechanical properties and adhesion of magnetron-sputtered Ti1-x-y-zAlxTaySizN coatings was studied. According to the energy-dispersive X-ray spectroscopy analysis, the coatings studied had the following chemical compositions: Ti0.41Al0.49Si0.10N, Ti0.38Al0.47Ta0.05Si0.10N, Ti0.36Al0.44Ta0.10Si0.10N and Ti0.35Al0.40Ta0.15Si0.10N. The X-ray diffraction experiments revealed the B1-type fcc crystal structure of the coatings. The increasing Ta content was found to induce the texture evolution from (200) to (111), which was attributed to a significant increase in the residual compressive stress in the coatings. The hardness monotonically increased from 32.7 to 42.2 GPa with increasing the Ta content, while the reduced Young’s modulus decreased from 369 to 353 GPa. The adhesion of the coatings to the Ti substrate was evaluated by scratch testing. It was found that the Ti0.36Al0.44Ta0.10Si0.10N coating was characterized by maximum adhesion strength, while incorporation of a larger amount of Ta resulted in earlier coating spallation due to the high residual compressive stress. Full article
(This article belongs to the Special Issue Friction and Wear of Coatings/Films)
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11 pages, 1971 KiB  
Article
Friction Reduction Due to Heating in the Sliding Contact of Smart Coating: Modeling of Mutual Effect
by Elena Torskaya and Fedor Stepanov
Lubricants 2022, 10(7), 165; https://doi.org/10.3390/lubricants10070165 - 20 Jul 2022
Cited by 2 | Viewed by 1428
Abstract
In smart coatings designed for friction units operating in wide temperature ranges, the material reacts to heating by changing its frictional properties. Appropriate experimental studies are available. In this paper, a model is proposed for studying the mutual effect of frictional heating, which [...] Read more.
In smart coatings designed for friction units operating in wide temperature ranges, the material reacts to heating by changing its frictional properties. Appropriate experimental studies are available. In this paper, a model is proposed for studying the mutual effect of frictional heating, which is inhomogeneous in the contact area, and shear stresses. The distribution of the latter differs from the Amonton–Coulomb law according to local temperatures, from which the local friction coefficient depends. Two problems are independently solved in the model: the problem of elastic contact between a smooth slider and a two-layer elastic half-space, and the thermal problem. The solution methods are numerical–analytical and are based on Hankel integral transforms and iterative procedures. The problem has been solved for two types of sliders simulating pin-on-disk and ball-on-disk test schemes. For the selected dependences of the local friction coefficient on temperature, an analysis was made to study the influence of sliding velocity and coating thickness on the distribution of temperatures, tangential stresses in the contact zone, as well as integral friction force. Relatively rigid and relatively compliant coatings were considered. It was found that for such smart coatings, which implement the mechanism of self-lubrication during frictional heating, there is a decrease in the friction force with increasing velocity, especially for relatively thick coatings with low thermal conductivity. Full article
(This article belongs to the Special Issue Friction and Wear of Coatings/Films)
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8 pages, 3123 KiB  
Article
Effect of sp3–sp2 Transformation on the Wear Rate of the DLC Coating
by Iosif Gershman, Alexander Mironov, Alexei Mezrin, Elena Torskaya, Tatyana Kuznetsova, Vasilina Lapitskaya and Alexander Rogachev
Lubricants 2022, 10(5), 85; https://doi.org/10.3390/lubricants10050085 - 04 May 2022
Cited by 8 | Viewed by 1981
Abstract
Based on the methods of non-equilibrium thermodynamics, it was found that the implementation of spontaneous processes with positive entropy production during friction leads to an increase in the wear intensity. Non-spontaneous processes with negative entropy production lead to a decrease in wear intensity. [...] Read more.
Based on the methods of non-equilibrium thermodynamics, it was found that the implementation of spontaneous processes with positive entropy production during friction leads to an increase in the wear intensity. Non-spontaneous processes with negative entropy production lead to a decrease in wear intensity. The tribological characteristics of diamond-like carbon (DLC) with different silicon content were studied. The wear intensity practically does not correlate with the friction coefficient. It is shown that DLC with the highest content of diamond-like inclusions (sp3) in the coating has the highest wear rate. In the same DLC, the most intense sp3–sp2 transformation during friction was observed. The sp3–sp2 transformation is a spontaneous process. Full article
(This article belongs to the Special Issue Friction and Wear of Coatings/Films)
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Review

Jump to: Research

45 pages, 21373 KiB  
Review
Effects of Element Doping on the Structure and Properties of Diamond-like Carbon Films: A Review
by Haibo Sun, Lv Yang, Huaichao Wu and Limei Zhao
Lubricants 2023, 11(4), 186; https://doi.org/10.3390/lubricants11040186 - 21 Apr 2023
Cited by 6 | Viewed by 2666
Abstract
Diamond-like carbon (DLC) films with excellent anti-friction and wear resistance, can effectively reduce the energy loss of tribosystems and the wear failure of parts, but the high residual stress limits their application and service life. Researchers found that doping heterogeneous elements in the [...] Read more.
Diamond-like carbon (DLC) films with excellent anti-friction and wear resistance, can effectively reduce the energy loss of tribosystems and the wear failure of parts, but the high residual stress limits their application and service life. Researchers found that doping heterogeneous elements in the carbon matrix can alleviate the defects in the microstructure and properties of DLC films (reduce the residual stress; enhance adhesion strength; improve tribological, corrosion resistance, hydrophobic, biocompatibility, and optical properties), and doping elements with different properties will have different effects on the structure and properties of DLC films. In addition, the comprehensive properties of DLC films can be coordinated by controlling the doping elements and their contents. In this paper, the effects of single element and co-doping of carbide-forming elements (Nb, W, Mo, Cr, Ti, Si) and non-carbide-forming elements (Cu, Al, Ag, Ni) on the properties of microstructure, mechanical, tribological, optical, hydrophobic, corrosion resistance, etc. of DLC films are reviewed. The mechanisms of the effects of doping elements on the different properties of DLC films are summarized and analyzed. Full article
(This article belongs to the Special Issue Friction and Wear of Coatings/Films)
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