Recent Advances in Green Tribology

A special issue of Coatings (ISSN 2079-6412).

Deadline for manuscript submissions: closed (15 August 2020) | Viewed by 18306

Special Issue Editors


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Guest Editor
Department of Marine Science and Technology, University of Oviedo, 33203 Gijon, Asturias, Spain
Interests: thermal spray; laser cladding; DLC and PVD coatings; green tribology; energy efficiency; biodegradability and bacterial toxicity of lubricants; tribological properties of ionic liquids as lubricant additives and as neat lubricants; nanoparticles as lubricant additives; wear mechanisms; real-time lubricant condition monitoring
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E-Mail Website
Guest Editor
Department of Construction and Manufacturing Engineering, University of Oviedo, 33203 Gijón, Asturias, Spain
Interests: green tribology; corrosion properties of lubricants; lubricant degradation mechanisms; biodegradability and bacterial toxicity of lubricants; tribological properties of ionic liquids as lubricant additives and as neat lubricants; nanoparticles as lubricant additives; DLC and PVD coatings; real-time lubricant condition monitoring
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Tribology is intrinsically linked to the environment, since its main purpose is to reduce the friction and wear of mechanical systems. This does not only involve an obvious economic benefit (already widely studied by several authors) but also a tangible benefit from an environmental point of view (the improvement of energy efficiency and reduction of associated emissions of the greenhouse effect, the improvement of the durability of materials and consequent decrease in the demand for raw materials, etc.). However, today, to design materials or lubricants capable of working efficiently in the most demanding and varied scenarios is not enough. At present, the design and manufacture of tribological applications must also be environmentally acceptable; that is, it must minimize the impact on the environment caused during its manufacture, use, disposal or recovery.

Likewise, recent advances in the study of efficient and environmentally friendly tribological applications that accelerate the energy transition towards renewable energies (wind turbines, tidal turbines, etc.) are of interest.

Innovation under an environmental sustainability approach, in the tribological areas of the development of new materials and surfaces, the design of more efficient tribological pairs, and the design of new lubricants and additives, etc. will be a source of competitive advantage, fundamental for the industry, in the coming years. The aim of this Special Issue is to present the recent advances in green tribology through a combination of original research papers and review articles from the outstanding researchers in this field.

In particular, the topics of interest include but are not limited to:

  • Biodegradable and environmentally friendly lubricants;
  • Tribology of renewable sources of energy;
  • Coatings, surface texturing, and minimization of heat and energy dissipation;
  • Biomimetic surfaces;
  • Real-time lubricant condition monitoring.

Dr. Rubén González
Dr. José L. Viesca
Guest Editors

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Published Papers (5 papers)

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Research

16 pages, 6014 KiB  
Article
Friction, Wear and Corrosion Behavior of Environmentally-Friendly Fatty Acid Ionic Liquids
by Javier Faes, Rubén González, Antolin Hernández Battez, David Blanco, Alfonso Fernández-González and José Luis Viesca
Coatings 2021, 11(1), 21; https://doi.org/10.3390/coatings11010021 - 27 Dec 2020
Cited by 5 | Viewed by 2421
Abstract
This research deals with the tribological behavior and corrosion performance of three novel fatty acid anion-based ionic liquids (FAILs): methyltrioctylammonium hexanoate ([N8,8,8,1][C6:0]), methyltrioctylammonium octadecanoate ([N8,8,8,1][C18:0]) and methyltrioctylammonium octadec-9-enoate ([N8,8,8,1][C18:1]), employed for [...] Read more.
This research deals with the tribological behavior and corrosion performance of three novel fatty acid anion-based ionic liquids (FAILs): methyltrioctylammonium hexanoate ([N8,8,8,1][C6:0]), methyltrioctylammonium octadecanoate ([N8,8,8,1][C18:0]) and methyltrioctylammonium octadec-9-enoate ([N8,8,8,1][C18:1]), employed for the first time as neat lubricant with five different material pairs: steel–steel, steel–aluminum alloy, steel–bronze, steel–cast iron and steel–tungsten carbide. These novel substances were previously obtained from fatty acids via metathesis reactions, identified structurally via NMR (nuclear magnetic resonance) and FTIR (Fourier-transform infrared spectroscopy) techniques, and then characterized from a physicochemical (density, water solubility, viscosity, viscosity index and refractive index) and environmental (bacterial toxicity and biodegradability) points of view. The corrosion behavior of the three FAILs was studied by exposure at room temperature, while friction and wear tests were performed with a reciprocating ball-on-disc configuration. The main results and conclusions obtained were: (1) Corrosion in the presence of the three FAILs is observed only on the bronze surface; (2) All FAILs presented similar tribological behavior as lubricants for each tested material pair; (3) XPS (X-ray photoelectron spectroscopy) analysis indicated that the surface behavior of the three FAILs in each material pair was similar, with low chemical interaction with the surfaces. Full article
(This article belongs to the Special Issue Recent Advances in Green Tribology)
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16 pages, 6572 KiB  
Article
Surface Treatments Solutions to Green Tribology
by Amaya Igartua, Gemma Mendoza, Xana Fernandez, Borja Zabala, Alberto Alberdi, Raquel Bayon and Ana Aranzabe
Coatings 2020, 10(7), 634; https://doi.org/10.3390/coatings10070634 - 30 Jun 2020
Cited by 2 | Viewed by 3121
Abstract
The objective of this paper is to highlight the need to combine lifecycle environmental assessment with durability evaluation (tribology and engine tests) to evaluate the potential of surface technologies to contribute to the green deal, in order to make Europe the first climate-neutral [...] Read more.
The objective of this paper is to highlight the need to combine lifecycle environmental assessment with durability evaluation (tribology and engine tests) to evaluate the potential of surface technologies to contribute to the green deal, in order to make Europe the first climate-neutral continent. Tribology is a scientific discipline that allows one to understand the system reaction to friction and wear. Tribological testing machines are prepared to measure friction at the laboratory level to minimize the wear and heat dissipation of two bodies in relative movement, thus improving the energy efficiency and minimizing CO2 emissions. In this paper, different surface technologies, such as high-velocity oxyfuel (HVOF), physical vapor deposition (PVD), and clean Cr electrolytic processes, are analyzed as promising surface technology solutions from both performance and environmental impact perspectives to replace harmful Cr(VI) coatings. The tribology simulates the working conditions of the real system at the laboratory level, reproducing the failure mechanism and facilitating the laboratory screening of the energy efficiency and durability of materials solutions for certain tribological systems—in this case, engine components. The tribological test results give information about the behavior of materials, while the engine tests gives information about the behavior of components. In this paper, the environmental impact of the production process of the coatings is also analyzed. Two hard chrome processes are compared, demonstrating that by controlling the production process it is possible to significantly reduce the environmental impact of the chrome-plated process, minimizing the environmental impact to that of PVD coatings. The environmental impact of the tested HVOF process is lower than traditional Cr(VI)-plated coatings but higher than PVD coatings. Combining the information from the lifecycle assessment (LCA) and tribological studies, it is possible to assess both the performance and the environmental impact of the surface treatments. This methodology is a tool to that can be used minimize CO2 emissions at the design phase to improve the energy efficiency of products and processes. Full article
(This article belongs to the Special Issue Recent Advances in Green Tribology)
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15 pages, 10570 KiB  
Article
Effect of Ionicity of Three Protic Ionic Liquids as Neat Lubricants and Lubricant Additives to a Biolubricant
by Hong Guo, Angela Rina Adukure and Patricia Iglesias
Coatings 2019, 9(11), 713; https://doi.org/10.3390/coatings9110713 - 31 Oct 2019
Cited by 15 | Viewed by 3168
Abstract
Friction and wear of sliding surfaces are responsible for important energy losses and negative environmental effects. The use of environmentally friendly and cost-effective protic ionic liquids as neat lubricants and lubricant additives has the potential to increase the efficiency and durability of mechanical [...] Read more.
Friction and wear of sliding surfaces are responsible for important energy losses and negative environmental effects. The use of environmentally friendly and cost-effective protic ionic liquids as neat lubricants and lubricant additives has the potential to increase the efficiency and durability of mechanical components without increasing the environmental damage. In this work, three halogen-free protic ionic liquids with increasing extent of ionicity, 2-hydroxyethylammonium 2-ethylhexanoate, 2-hydroxymethylammonium 2-ethylhexancate, and 2-hydroxydimethylammonium 2-ethylhexanoate, were synthesized and studied as neat lubricants and additives to a biodegradable oil in a steel–steel contact. The results show that the use of any protic ionic liquid as a neat lubricant or lubricant additive reduced friction and wear with respect to the biodegradable oil. The ionic liquid with the lowest ionicity reached the highest wear reduction. The one possessing the highest ionicity presented the poorest friction and wear behaviors as a neat lubricant, probably due to the more ionic nature of this liquid, which promoted tribocorrosion reactions on the steel surface. This ionic liquid performed better as an additive, showing that a small addition of this liquid in a biodegradable oil is enough to form protective layers on steel surfaces. However, it is not enough to accelerate the wear process with detrimental tribocorrosion reactions. Full article
(This article belongs to the Special Issue Recent Advances in Green Tribology)
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10 pages, 3645 KiB  
Article
Fatty Acid-Derived Ionic Liquid Lubricant. Protic Ionic Liquid Crystals as Protic Ionic Liquid Additives
by María-Dolores Avilés, Ramón Pamies, José Sanes, Francisco-José Carrión and María-Dolores Bermúdez
Coatings 2019, 9(11), 710; https://doi.org/10.3390/coatings9110710 - 31 Oct 2019
Cited by 17 | Viewed by 3560
Abstract
Fatty acids are natural products which have been studied as green lubricants. Ionic liquids are considered efficient friction reducing and wear preventing lubricants and lubricant additives. Fatty acid-derived ionic liquids have shown potential as neat lubricant and additives. Protic ionic liquid crystals (PILCs) [...] Read more.
Fatty acids are natural products which have been studied as green lubricants. Ionic liquids are considered efficient friction reducing and wear preventing lubricants and lubricant additives. Fatty acid-derived ionic liquids have shown potential as neat lubricant and additives. Protic ionic liquid crystals (PILCs) are protic ionic liquids (PILs) where cations and anions form ordered mesophases that show liquid crystalline behavior. The adsorption of carboxylate units on sliding surfaces can enhance the lubricant performance. Ionic liquid crystal lubricants with longer alkyl chains can separate sliding surfaces more efficiently. However, they are usually solid at room temperature and, when used as additives in water, transitions to high friction coefficients and wear rates, with tribocorrosion processes occur when water evaporation takes place at the interface. In order to avoid these inconveniences, in the present work, a protic ammonium palmitate (DPA) ionic liquid crystal has been added in 1 wt.% proportion to a short chain citrate ionic liquid (DCi) with the same protic ammonium cation. A spin coated layer of (DCi + DPA) was deposited on AISI316L steel surface before the sliding test against sapphire ball. Synergy between DCi PIL and DPA PILC additive reduces friction coefficient and wear rate, without tribocorrosion processes, as shown by scanning electron microscopy (SEM)/energy dispersive X-ray microanalysis (EDX) and X-ray photoelectron spectroscopy (XPS) results. Full article
(This article belongs to the Special Issue Recent Advances in Green Tribology)
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17 pages, 5543 KiB  
Article
Tribological and Thermophysical Properties of Environmentally-Friendly Lubricants Based on Trimethylolpropane Trioleate with Hexagonal Boron Nitride Nanoparticles as an Additive
by José M. Liñeira del Río, María J. G. Guimarey, María J. P. Comuñas, Enriqueta R. López, Jose I. Prado, Luis Lugo and Josefa Fernández
Coatings 2019, 9(8), 509; https://doi.org/10.3390/coatings9080509 - 12 Aug 2019
Cited by 23 | Viewed by 5289
Abstract
Dispersions based on hexagonal boron nitride, h-BN, nanoparticles, at 0.50, 0.75 and 1.0 wt.% mass concentrations, in an ester base oil composed mainly of trimethylolpropane trioleate, were investigated as potential nanolubricants. The stability of the dispersions was assessed to determine the reliability of [...] Read more.
Dispersions based on hexagonal boron nitride, h-BN, nanoparticles, at 0.50, 0.75 and 1.0 wt.% mass concentrations, in an ester base oil composed mainly of trimethylolpropane trioleate, were investigated as potential nanolubricants. The stability of the dispersions was assessed to determine the reliability of the tribological, thermophysical and rheological measurements. Density and viscosity were measured from 278.15 to 373.15 K, while rheological behavior was analyzed at shear rates from 1 to 1000 s−1 at 283.15 K. Newtonian behavior was exhibited by all nanolubricants at the explored conditions, with the exception of the highest concentration at the lowest shear rates, where possible non-Newtonian behavior was observed. Tribological tests were performed under a normal load of 2.5 N. Wear was evaluated by means of a 3D profiler, scanning electron microscopy and confocal Raman microscopy. The best tribological performance was achieved by the 0.75 wt.% nanolubricant, with reductions of 25% in the friction coefficient, 9% in the scar width, 14% in the scar depth, and 22% of the transversal area, all with respect to the neat oil. It was observed that physical protective tribofilms are created between rubbing surfaces. Full article
(This article belongs to the Special Issue Recent Advances in Green Tribology)
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