Lubricants

27 pages, 7572 KiB

Open AccessReview

Applications of Diamond to Improve Tribological Performance in the Oil and Gas Industry

by David W. Wheeler

AWE plc, Aldermaston, Reading, Berkshire RG7 4PR, UK

Lubricants 2018, 6(3), 84; https://doi.org/10.3390/lubricants6030084 - 18 Sep 2018

Cited by 15 | Viewed by 6983

The use of diamond in tribological applications in the oil and gas industry is reviewed. The high hardness, strength, and corrosion resistance of diamond make it an attractive option for components that are susceptible to degradation by abrasive, erosive, or adhesive wear; such [...] Read more.

The use of diamond in tribological applications in the oil and gas industry is reviewed. The high hardness, strength, and corrosion resistance of diamond make it an attractive option for components that are susceptible to degradation by abrasive, erosive, or adhesive wear; such components may also be prone to corrosion owing to the nature of the environments to which they are often exposed. Applications such as drill bits, bearings, and mechanical seals benefit from the use of diamond, while choke valves are the subject of research programs to assess the suitability of chemical vapor deposition (CVD) diamond for these components. Also discussed are some of the conditions experienced by the components and how the properties of diamond enhance their operating lives. Full article

(This article belongs to the Special Issue Oil and Gas Tribology)

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12 pages, 3751 KiB

Open AccessArticle

Multiscale Modeling Applied to the Hydrodynamic Lubrication of Rough Surfaces for Computation Time Reduction

by Noël Brunetière^1,*,†

and Arthur Francisco^2,†

¹ Institut Pprime, CNRS, Université de Poitiers, ISAE-ENSMA, 86962 Futuroscope Chasseneuil, France

² Institut Pprime, CNRS, Université de Poitiers, ISAE-ENSMA, 16021 Angoulême, France

^† These authors contributed equally to this work.

Lubricants 2018, 6(3), 83; https://doi.org/10.3390/lubricants6030083 - 15 Sep 2018

Cited by 6 | Viewed by 4258

Abstract

This paper presents a multiscale finite element method applied to the simulation of a lubricating film flowing between rough surfaces. The objective of this approach is to study flows between large rough surfaces needing very fine meshes while maintaining a reasonable computation time. [...] Read more.

This paper presents a multiscale finite element method applied to the simulation of a lubricating film flowing between rough surfaces. The objective of this approach is to study flows between large rough surfaces needing very fine meshes while maintaining a reasonable computation time. For this purpose, the domain is split into a number of subdomains (bottom-scale meshes) connected by a coarse mesh (top-scale). The pressure distribution at the top-scale is used as boundary conditions for the bottom-scale problems. This pressure is adjusted to ensure global mass flow balance between the contiguous subdomains. This multiscale method allows for a significant reduction of the number of operations as well as a satisfactory accuracy of the results if the top-scale mesh is properly fitted to the roughness lateral scale. Furthermore the present method is well-suited to parallel computation, leading to much more significant computation time reduction. Full article

(This article belongs to the Special Issue Multiphysics and Multiscale Models of Tribology)

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18 pages, 7486 KiB

Open AccessArticle

An Experimental Study on Starved Grease Lubricated Contacts

by David E. P. Gonçalves^1,*

, Armando V. Campos²

and Jorge H. O. Seabra³

¹ INEGI, Universidade do Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto, Portugal

² ISEP-IPP, Instituto Superior de Engenharia do Porto, 4200-072 Porto, Portugal

³ FEUP, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto, Portugal

Lubricants 2018, 6(3), 82; https://doi.org/10.3390/lubricants6030082 - 10 Sep 2018

Cited by 13 | Viewed by 5408

Abstract

The film thickness of a ball-on-disc contact lubricated with four greases of different formulations was measured under different operating conditions until starvation. Two polymer-thickened greases and two lithium-thickened greases, formulated with base oils of different nature and/or viscosity, were tested. The central film [...] Read more.

The film thickness of a ball-on-disc contact lubricated with four greases of different formulations was measured under different operating conditions until starvation. Two polymer-thickened greases and two lithium-thickened greases, formulated with base oils of different nature and/or viscosity, were tested. The central film thickness was measured under constant operating conditions (load, temperature, slide-to-roll ratio) varying only the entrainment speed. In a separate test, the film thickness was measured over time with all operating conditions set to constant. Pictures of the film thickness profile across the contact area were also registered. The results were compared with the fully flooded results. The coefficient of friction (COF) was measured in a ball-on-disc contact under equal operating conditions and the results were correlated with the film thickness findings. The different grease formulations and the influence of the operating conditions on the film thickness and COF were discussed. The polymer thickened the greases, promoting lower COF and higher film thickness, especially when there is thickener material crossing the contact which happens quite often for these greases. Full article

(This article belongs to the Special Issue Advances in Polymer Tribology)

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15 pages, 7302 KiB

Open AccessArticle

Measured and Predicted Operating Characteristics of a Tilting-Pad Journal Bearing with Jacking-Oil Device at Hydrostatic, Hybrid, and Hydrodynamic Operation

by Thomas Hagemann^*

, Peter Pfeiffer and Hubert Schwarze

Institute of Tribology and Energy Conversion Machinery, Clausthal University of Technology, 38678 Clausthal-Zellerfeld, Germany

Lubricants 2018, 6(3), 81; https://doi.org/10.3390/lubricants6030081 - 10 Sep 2018

Cited by 12 | Viewed by 8369

Abstract

Jacking-oil pockets are applied in many journals and thrust bearing applications in order to provide a hydrostatic oil film force that ensures a wear free run-up following a successful lift-off procedure. However, all components of the jacking-oil system have to be carefully designed [...] Read more.

Jacking-oil pockets are applied in many journals and thrust bearing applications in order to provide a hydrostatic oil film force that ensures a wear free run-up following a successful lift-off procedure. However, all components of the jacking-oil system have to be carefully designed in order to limit costs and prevent significant disturbance of hydrodynamic operation after deactivation of lift-oil. Experimental data and predictions for a four-pad tilting-pad journal bearing in load between pivot configuration are presented. Dynamic processes of the lift-off procedure as well as characteristic parameters of stationary conditions are studied. Moreover, hydrodynamic operation and hybrid lubrication providing a combined hydrodynamic and hydrostatic pressure distribution are investigated for sliding speeds up to 20 m/s. Analyzes of lift-off procedure prove that characteristic parameters such as lift-off pressures and vertical lift displacements are considerably influenced by manufacturing tolerances and misalignments. The comparison of hydrodynamic and hybrid lubrication provides a significant increase of load carrying capacity by additional jacking-oil supply at the maximum journal speed. In summary, results of measurements and predictions correlate well for all three investigated lubrication conditions. Full article

(This article belongs to the Special Issue Fluid-Film Lubrication)

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11 pages, 2082 KiB

Open AccessArticle

Analytical Formula for the Ratio of Central to Minimum Film Thickness in a Circular EHL Contact

by Petr Sperka^*

, Ivan Krupka and Martin Hartl

Faculty of Mechanical Engineering, Brno University of Technology, Technicka 2896/2, 616 69 Brno, Czech Republic

Lubricants 2018, 6(3), 80; https://doi.org/10.3390/lubricants6030080 - 7 Sep 2018

Cited by 14 | Viewed by 6959

Abstract

Prediction of minimum film thickness is often used in practice for calculation of film parameter to design machine operation in full film regime. It was reported several times that majority of prediction formulas cannot match experimental data in terms of minimum film thickness. [...] Read more.

Prediction of minimum film thickness is often used in practice for calculation of film parameter to design machine operation in full film regime. It was reported several times that majority of prediction formulas cannot match experimental data in terms of minimum film thickness. These standard prediction formulas give almost constant ratio between central and minimum film thickness while numerical calculations show ratio which spans from 1 to more than 3 depending on M and L parameters. In this paper, an analytical formula of this ratio is presented for lubricants with various pressure–viscosity coefficients. The analytical formula is compared with optical interferometry measurements and differences are discussed. It allows better prediction, compared to standard formulas, of minimum film thickness for wide range of M and L parameters. Full article

(This article belongs to the Special Issue Fluid-Film Lubrication)

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11 pages, 4687 KiB

Open AccessArticle

Impact of Fuel Contents on Tribological Performance of PAO Base Oil and ZDDP

by Yan Zhou^1,*, Weimin Li^1,2, Benjamin C. Stump¹, Raynella M. Connatser³

, Sladjan Lazarevic¹

and Jun Qu^1,*

¹ Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

² State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 73000, China

³ Energy and Transportation Science Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

Lubricants 2018, 6(3), 79; https://doi.org/10.3390/lubricants6030079 - 7 Sep 2018

Cited by 11 | Viewed by 5622

Abstract

Fuel and water contents are inevitable in automotive engine oils. This study intends to investigate the impact of the addition of gasoline (3–20%) and water (1%) on the lubricating performance of synthetic base oil (PAO), with or without an anti-wear additive (ZDDP), for [...] Read more.

Fuel and water contents are inevitable in automotive engine oils. This study intends to investigate the impact of the addition of gasoline (3–20%) and water (1%) on the lubricating performance of synthetic base oil (PAO), with or without an anti-wear additive (ZDDP), for a steel-cast iron contact. Fuel-added PAO showed an increase in the load carrying capacity. Oil electrical conductivity and total acid number (TAN) measurements showed slightly increased conductivity and marginally increased acidity at a higher fuel concentration. In contrast, an increased wear rate, proportional to the fuel concentration, was observed in a prolonged test with constant-loading. Results suggested that the fuel addition is a double-edged sword: reducing the scuffing risk by providing stronger surface adsorption and increasing the sliding wear rate by bringing down the oil viscosity. The PAO-water blend formed an emulsion and resulted in a significantly increased load-carrying capacity, again likely due to the higher polarity and possibly acidity. For the ZDDP-containing PAO, the addition of 1% water and 3% fuel generated 24% and 52% higher wear. The phosphate polymerization level was reduced on the worn surfaces by the introduction of water but the thickness of ZDDP tribofilm was not significantly affected. Full article

(This article belongs to the Special Issue Advanced Lubrication for Energy Efficiency)

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25 pages, 3031 KiB

Open AccessArticle

On the Two-Scale Modelling of Elastohydrodynamic Lubrication in Tilted-Pad Bearings

by Gregory De Boer^1,*

and Andreas Almqvist²

¹ School of Mechanical Engineering, University of Leeds, LS2 9JT Leeds, UK

² Division of Machine Elements, Luleå University of Technology, E837a Luleå, Sweden

Lubricants 2018, 6(3), 78; https://doi.org/10.3390/lubricants6030078 - 3 Sep 2018

Cited by 12 | Viewed by 4423

Abstract

A two-scale method for modelling the Elastohydrodynamic Lubrication (EHL) of tilted-pad bearings is derived and a range of solutions are presented. The method is developed from previous publications and is based on the Heterogeneous Multiscale Methods (HMM). It facilitates, by means of homogenization, [...] Read more.

A two-scale method for modelling the Elastohydrodynamic Lubrication (EHL) of tilted-pad bearings is derived and a range of solutions are presented. The method is developed from previous publications and is based on the Heterogeneous Multiscale Methods (HMM). It facilitates, by means of homogenization, incorporating the effects of surface topography in the analysis of tilted-pad bearings. New to this article is the investigation of three-dimensional bearings, including the effects of both ideal and real surface topographies, micro-cavitation, and the metamodeling procedure used in coupling the problem scales. Solutions for smooth bearing surfaces, and under pure hydrodynamic operating conditions, obtained with the present two-scale EHL model, demonstrate equivalence to those obtained from well-established homogenization methods. Solutions obtained for elastohydrodynamic operating conditions, show a dependency of the solution to the pad thickness and load capacity of the bearing. More precisely, the response for the real surface topography was found to be stiffer in comparison to the ideal. Micro-scale results demonstrate periodicity of the flow and surface topography and this is consistent with the requirements of the HMM. The means of selecting micro-scale simulations based on intermediate macro-scale solutions, in the metamodeling approach, was developed for larger dimensionality and subsequent calibration. An analysis of the present metamodeling approach indicates improved performance in comparison to previous studies. Full article

(This article belongs to the Special Issue Multiphysics and Multiscale Models of Tribology)

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25 pages, 10009 KiB

Open AccessArticle

Parametric and Optimization Study of Rectangular-Rounded, Hydraulic, Elastomeric, Reciprocating Seals at Temperatures between −54 and +135 °C

by George K. Nikas

KADMOS Engineering Ltd., 3 Princes Mews, Hounslow TW3 3RF, UK

Lubricants 2018, 6(3), 77; https://doi.org/10.3390/lubricants6030077 - 1 Sep 2018

Cited by 11 | Viewed by 5978

Abstract

Hydraulic, reciprocating, polymeric seals are met in many engineering applications and are critical components for mechanism and machine reliability in industries including the automotive, marine, and aerospace industries. A parametric and optimization study of rectangular-rounded, hydraulic, reciprocating, elastomeric rod seals at −54, +23, [...] Read more.

Hydraulic, reciprocating, polymeric seals are met in many engineering applications and are critical components for mechanism and machine reliability in industries including the automotive, marine, and aerospace industries. A parametric and optimization study of rectangular-rounded, hydraulic, reciprocating, elastomeric rod seals at −54, +23, and +135 °C is presented, which is particularly relevant to hydraulic actuators in aircraft landing gear. Parametric optimization not only improves performance, but also helps avoid sealing failures. The calculations were based on a physically based, deterministic mathematical model of such seals, experimentally validated at the aforementioned temperatures and recently published by the author. The parameters varied were the seal axial width and corner radius, seal elastic modulus, sealed pressure, stroking velocity, operating temperature, rod surface roughness, seal radial interference, and seal swelling by fluid uptake. Their influence was established based on the following performance variables: leakage rate, frictional force, coefficient of friction, temperature rise in the sealing contact, lambda ratio (proportional to the average film thickness in the contact), and ratio of the asperity friction force to the total friction force. The parametric study greatly facilitates the selection of optimal values of the analyzed parameters to minimize leakage, friction, and wear, either concurrently as a set or individually, depending on application priorities. Full article

(This article belongs to the Special Issue Fluid-Film Lubrication)

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18 pages, 6846 KiB

Open AccessArticle

Improved Tribocorrosion Resistance of a CoCrMo Implant Material by Carburising

by Josianne Cassar¹, Bertram Mallia^1,*

, Antonino Mazzonello¹, Andreas Karl² and Joseph Buhagiar¹

¹ Department of Metallurgy and Materials Engineering, University of Malta, Msida MSD 2080, Malta

² Bodycote Hardiff GmbH, 86899 Landsberg, Germany

Lubricants 2018, 6(3), 76; https://doi.org/10.3390/lubricants6030076 - 28 Aug 2018

Cited by 11 | Viewed by 4869

Abstract

Tribocorrosion damage is a cause for the premature failure of hip implants made of cobalt-based alloys. Low-temperature carburising can be a plausible solution towards mitigating the tribocorrosion damage of articulating components. This diffusion treatment introduces a supersaturated carbon solid solution, termed S-phase, which [...] Read more.

Tribocorrosion damage is a cause for the premature failure of hip implants made of cobalt-based alloys. Low-temperature carburising can be a plausible solution towards mitigating the tribocorrosion damage of articulating components. This diffusion treatment introduces a supersaturated carbon solid solution, termed S-phase, which hardens the CoCrMo alloy without detriment to the corrosion resistance. This work investigates and compares the tribocorrosion behaviour of untreated and carburised ASTM F1537 CoCrMo alloys tested in Ringer’s solution using a reciprocating sliding configuration against a polycrystalline alumina counterface under different electrochemical conditions. The research shows that whereas the carburised alloy suffered a slightly higher wear loss under a cathodic potential, it was able to reduce the material losses considerably when tested under both open circuit and anodic potential conditions. Under anodic conditions material losses by corrosion due to wear dominated. The better tribocorrosion resistance of the carburised layer was attributed to the better qualities of the passive film for the carburised sample coupled with an increased load support. Full article

(This article belongs to the Special Issue Tribocorrosion of Surface Engineered Materials)

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16 pages, 6675 KiB

Open AccessArticle

Cavitation Growth Phenomena in Pure-Sliding Grease EHD Contacts

by Takefumi Otsu^1,*, Romeo Glovnea² and Joichi Sugimura³

¹ Division of Mechatronics, Department of Innovative Engineering, Faculty of Science and Technology, Oita University, 700 Dannoharu, Oita 870-1192, Japan

² Department of Engineering and Design, University of Sussex, Brighton BN1 9RH, UK

³ International Institute for Carbon-Neutral Energy Research, Kyushu University, Fukuoka 819-0395, Japan

Lubricants 2018, 6(3), 75; https://doi.org/10.3390/lubricants6030075 - 22 Aug 2018

Cited by 1 | Viewed by 4729

Abstract

This article describes experimental and theoretical studies on the cavitation phenomena in the grease lubrication film under pure sliding elastohydrodynamic contact. In situ observation tests using the optical interferometry technique were conducted, and the growth of cavitation was captured using a high-speed camera. [...] Read more.

This article describes experimental and theoretical studies on the cavitation phenomena in the grease lubrication film under pure sliding elastohydrodynamic contact. In situ observation tests using the optical interferometry technique were conducted, and the growth of cavitation was captured using a high-speed camera. The results showed that the cavity grew in two stages, which was similar to the behavior in the base oil, and that the cavity growth rate in the initial stage was higher than that in the second stage. In the initial stage, the cavity growth time in the grease was longer than that in the base oil, and the cavity length after the growth depended on the base oil viscosity. It was also found in the test using diurea grease that small cavities were formed by the lumps of thickener. The cavity growth in the initial stage was discussed by numerical simulation of pressure distribution based on a simple rheological model. Full article

(This article belongs to the Special Issue Fluid-Film Lubrication)

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26 pages, 5202 KiB

Open AccessReview

Effect of Humidity on Friction and Wear—A Critical Review

by Zhe Chen¹, Xin He¹, Chen Xiao² and Seong H. Kim^1,2,*

¹ Department of Chemical Engineering and Materials Research Institute, Pennsylvania State University, University Park, PA 16802, USA

² Tribology Research Institute, State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031, China

Lubricants 2018, 6(3), 74; https://doi.org/10.3390/lubricants6030074 - 22 Aug 2018

Cited by 134 | Viewed by 14613

Abstract

The friction and wear behavior of materials are not intrinsic properties, but extrinsic properties; in other words, they can drastically vary depending on test and environmental conditions. In ambient air, humidity is one such extrinsic parameter. This paper reviews the effects of humidity [...] Read more.

The friction and wear behavior of materials are not intrinsic properties, but extrinsic properties; in other words, they can drastically vary depending on test and environmental conditions. In ambient air, humidity is one such extrinsic parameter. This paper reviews the effects of humidity on macro- and nano-scale friction and wear of various types of materials. The materials included in this review are graphite and graphene, diamond-like carbon (DLC) films, ultrananocrystalline diamond (UNCD), transition metal dichalcogenides (TMDs), hexagonal boron nitride (h-BN), boric acid, silicon, silicon oxide, silicates, advanced ceramics, and metals. Details of underlying mechanisms governing friction and wear behaviors vary depending on materials and humidity; nonetheless, a comparison of various material cases revealed an overarching trend. Tribochemical reactions between the tribo-materials and the adsorbed water molecules play significant roles; such reactions can occur at defect sites in the case of two-dimensionally layered materials and carbon-based materials, or even on low energy surfaces in the case of metals and oxide materials. It is extremely important to consider the effects of adsorbed water layer thickness and structure for a full understanding of tribological properties of materials in ambient air. Full article

(This article belongs to the Special Issue Advanced Lubrication for Energy Efficiency)

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9 pages, 1223 KiB

Open AccessArticle

PAO Contributions to Energy Efficiency in 0W-20 Passenger Car Engine Oils

by Ken Hope

Chevron Phillips Chemical Company LP, The Woodlands, TX 77380, USA

Lubricants 2018, 6(3), 73; https://doi.org/10.3390/lubricants6030073 - 22 Aug 2018

Cited by 16 | Viewed by 8925

Abstract

Energy efficiency improvements continue to be a significant challenge to the transportation and lubricant industries. Many areas are being examined to increase energy efficiency in lubricants. This paper examines contributions from base oils in terms of friction reduction since friction reduction is related [...] Read more.

Energy efficiency improvements continue to be a significant challenge to the transportation and lubricant industries. Many areas are being examined to increase energy efficiency in lubricants. This paper examines contributions from base oils in terms of friction reduction since friction reduction is related to energy consumption. The impact of base oil on the frictional differences in a passenger car lubricant is studied using PAO and Group III base oils. Chemical and physical property differences are highlighted and the Stribeck and Traction curves have been measured using a Mini Traction Machine (MTM). Relating the differences in friction to the energy efficiency have been estimated based upon different lubrication regimes measured with the MTM. Reductions in energy losses due to cooling or exhaust have not been included so that any improvements are estimated on frictional differences alone. These frictional improvements are assumed to be related to the differences in chemical make-up of the base oils studied. Full article

(This article belongs to the Special Issue Advanced Lubrication for Energy Efficiency)

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14 pages, 2093 KiB

Open AccessReview

Opportunities and Challenges with Polyalkylene Glycol for Engine Oil Application

by Arup Gangopadhyay^1,* and John Cuthbert²

¹ Ford Motor Company, Dearborn, MI 48121, USA

² The Dow Chemical Company, Midland, MI 48674, USA

Lubricants 2018, 6(3), 72; https://doi.org/10.3390/lubricants6030072 - 21 Aug 2018

Cited by 8 | Viewed by 6260

Abstract

Base oil plays an important role in engine oil formulation in delivering overall performance attributes in addition to additives. Non-traditional base oil like polyalkylene glycol (PAG) did not get much attention in the past for formulating automotive engine oil. This investigation explored PAGs [...] Read more.

Base oil plays an important role in engine oil formulation in delivering overall performance attributes in addition to additives. Non-traditional base oil like polyalkylene glycol (PAG) did not get much attention in the past for formulating automotive engine oil. This investigation explored PAGs for enhancing engine oil performance primarily for fuel economy benefit over traditional mineral oil-based formulations. This paper highlights key findings from an extensive investigation, parts of which were published in detail elsewhere, and identifying opportunities and challenges. Several PAG chemistries were investigated depending on their feedstock material. Friction performance was evaluated by several methods starting with laboratory bench tests to engine components to chassis roll dynamometer tests. Durability was also evaluated from laboratory bench tests to engine components to ASTM sequence tests. The investigation revealed that significant friction reduction or fuel economy gain can be achieved with PAG oil but wear protection capability, piston deposit, and varnish require much improvement requiring identification/development of additive components. A few alternative routes for performance improvement are suggested. Full article

(This article belongs to the Special Issue Advanced Lubrication for Energy Efficiency)

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17 pages, 1198 KiB

Open AccessArticle

A Simulation Study for the Design of Membrane Restrictor in an Opposed-Pad Hydrostatic Bearing to Achieve High Static Stiffness

by Ta-Hua Lai¹

and Shih-Chieh Lin^2,*

¹ Department of Thermal Energy Conversion Technology, Industrial Technology Research Institute, 195, Sec. 4, Chung Hsing Rd., Chutung, Hsinchu 31057, Taiwan

² Department of Power Mechanical Engineering, National Tsing Hua University, 101, Sec. 2, Guang Fu Rd., Hsinchu 30013, Taiwan

Lubricants 2018, 6(3), 71; https://doi.org/10.3390/lubricants6030071 - 21 Aug 2018

Cited by 9 | Viewed by 5262

Abstract

The effects of a membrane restrictor’s design parameters on the performance of a hydrostatic opposed-pad bearing are presented in this article. Compared to the single-pad bearing, the opposed-pad bearing can perform much better in terms of static stiffness over a wider load range. [...] Read more.

The effects of a membrane restrictor’s design parameters on the performance of a hydrostatic opposed-pad bearing are presented in this article. Compared to the single-pad bearing, the opposed-pad bearing can perform much better in terms of static stiffness over a wider load range. It is also found that, for small bearing eccentricity, the optimal design restriction ratio of 0.25 still results in high bearing stiffness even if the dimensionless stiffness of membrane is not the optimal value of 1.33. Furthermore, decreasing the ratio of the upper effective area to the lower effective area generally increases the applicable working range of the bearing. Additionally, for high loading demands, the chance for further improvement of bearing performance by employing different design parameter for each pad is examined. Finally, a design procedure for designing the membrane restrictor for an opposed-pad bearing to achieve high static stiffness is given. Full article

(This article belongs to the Special Issue Fluid-Film Lubrication)

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19 pages, 4928 KiB

Open AccessArticle

Meta-Analysis Comparing Wettability Parameters and the Effect of Wettability on Friction Coefficient in Lubrication

by Michael J. Schertzer^* and Patricia Iglesias

Department of Mechanical Engineering, Rochester Institute of Technology, Rochester, NY 14623, USA

Lubricants 2018, 6(3), 70; https://doi.org/10.3390/lubricants6030070 - 15 Aug 2018

Cited by 16 | Viewed by 6079

Abstract

This work presents a meta-analysis that compares the suitability of various parameters used to characterize wettability in tribological systems. It also examines the relationship between wettability and the friction factor for multiple lubricant-surface pairings. The characterization of wetting behavior was similar when using [...] Read more.

This work presents a meta-analysis that compares the suitability of various parameters used to characterize wettability in tribological systems. It also examines the relationship between wettability and the friction factor for multiple lubricant-surface pairings. The characterization of wetting behavior was similar when using the contact angle between a lubricant and surface and various dimensional and dimensionless formulations of a spreading parameter. It was possible to identify hydrodynamic, boundary, and mixed lubrication regimes by combining a dimensionless wettability parameter with the specific film thickness for a variety of neat ionic liquids and magnetorheological fluids in contact with metallic, thermoplastic, and elastic surfaces. This characterization was possible using multiple dimensionless wettability parameters, but those that can be fully determined using only the contact angle may be preferred by experimentalists. The use of dimensional and dimensionless wettability parameters that included polar and disperse components of surface tension and surface energy did not appear to provide additional insight into the wettability or frictional performance for the tribological system examined here. Full article

(This article belongs to the Special Issue Ionic Liquids: Friction and Lubrication Mechanisms)

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11 pages, 15996 KiB

Open AccessArticle

Evaluation of Friction Behavior and Surface Interactions of Cyano-Based Ionic Liquids under Different Sliding Contacts and High Vacuum Condition

by Shouhei Kawada^1,*, Seiya Watanabe², Shinya Sasaki¹ and Masaaki Miyatake¹

¹ Department of Mechanical Engineering, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585, Japan

² Division of Surface and Corrosion Science, Kungliga Tekniska Högskolan, Stockholm SE-100 44, Sweden

Lubricants 2018, 6(3), 69; https://doi.org/10.3390/lubricants6030069 - 9 Aug 2018

Cited by 4 | Viewed by 4359

Abstract

The friction coefficients of ionic liquids were evaluated by many investigations. Most investigations used fluorine-based ionic liquids as lubricants. However, these ionic liquids produce the corrosion wear. This investigation focuses on the use of cyano-based ionic liquids as lubricants. Compared to fluorine-based ionic [...] Read more.

The friction coefficients of ionic liquids were evaluated by many investigations. Most investigations used fluorine-based ionic liquids as lubricants. However, these ionic liquids produce the corrosion wear. This investigation focuses on the use of cyano-based ionic liquids as lubricants. Compared to fluorine-based ionic liquids, cyano-based ionic liquids exhibit high friction coefficients against steel material. This work examines how the friction coefficients of cyano-based ionic liquids are influenced by the type of sliding material used (AISI 52100, TiO₂, and tetrahedral amorphous carbon). TiO₂ lubricated with 1-ethyl-3-methylimidazolium tricyanomethanide, and ta-C lubricated with 1-butyl-1methylpyrrolidinium tetracyanoborate exhibited very low friction coefficients, smaller than fluorine-based ionic liquids. Time-of-Flight Secondary Ion Mass Spectrometry analysis showed that anions adsorb onto the worn surface, suggesting that anion adsorption is a critical parameter influencing friction coefficients. Quadrupole Mass Spectrometry measurements revealed that cations decompose on the nascent surface, preventing adsorption on the worn surface. These results suggest that low friction coefficients require the decomposition of cations and adsorption of anions. The reactivity of nascent surface changes with the sliding material used due to varying catalytic activity of the nascent surfaces. Full article

(This article belongs to the Special Issue Ionic Liquids: Friction and Lubrication Mechanisms)

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15 pages, 1927 KiB

Open AccessReview

Common Properties of Lubricants that Affect Vehicle Fuel Efficiency: A North American Historical Perspective

by Mark T. Devlin

Afton Chemical Corporation, 500 Spring Street, Richmond, VA 23218, USA

Lubricants 2018, 6(3), 68; https://doi.org/10.3390/lubricants6030068 - 3 Aug 2018

Cited by 29 | Viewed by 8731

Abstract

The development of advanced lubricants to improve vehicle fuel efficiency can appear to be as simple as lowering the viscosity and frictional properties of a fluid. However, applied research studies have shown that it is quite difficult to quantify the fuel efficiency properties [...] Read more.

The development of advanced lubricants to improve vehicle fuel efficiency can appear to be as simple as lowering the viscosity and frictional properties of a fluid. However, applied research studies have shown that it is quite difficult to quantify the fuel efficiency properties of advanced lubricants in vehicles. A review of the historical research predominantly performed in North America in this area reveals that there are many factors to consider in order to demonstrate the effectiveness of advanced lubricants. First, the methodology used to measure vehicle fuel efficiency will impact the results since there are many factors not related to the lubricant which will influence vehicle fuel efficiency. Second, developing advanced fuel-efficient lubricants under well controlled conditions overlooks the issue that lubricant properties such as viscosity and friction affect the operating conditions encountered by the lubricant in the vehicle. Finally, the physical properties of lubricants that historically control fuel economy do not have the same effect on fuel efficiency in all vehicles. The proper vehicle or system level test needs to be selected to properly assess the benefits of new advanced lubricants. Full article

(This article belongs to the Special Issue Advanced Lubrication for Energy Efficiency)

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17 pages, 41076 KiB

Open AccessArticle

Comparative Study of Tribological Behavior of Electroless Ni–B, Ni–B–Mo, and Ni–B–W Coatings at Room and High Temperatures

by Arkadeb Mukhopadhyay¹

, Tapan Kumar Barman¹, Prasanta Sahoo^1,*

and J. Paulo Davim²

¹ Department of Mechanical Engineering, Jadavpur University, Kolkata 700032, India

² Department of Mechanical Engineering, University of Aveiro, 3810-193 Aveiro, Portugal

Lubricants 2018, 6(3), 67; https://doi.org/10.3390/lubricants6030067 - 2 Aug 2018

Cited by 29 | Viewed by 5325

Abstract

Ni–B alloys deposited by the electroless method are considered to be hard variants of the electroless nickel family. Inclusion of Mo or W to form ternary alloys improves the thermal stability of electroless nickel coatings. Therefore, in the present work, Ni–B, Ni–B–Mo, and [...] Read more.

Ni–B alloys deposited by the electroless method are considered to be hard variants of the electroless nickel family. Inclusion of Mo or W to form ternary alloys improves the thermal stability of electroless nickel coatings. Therefore, in the present work, Ni–B, Ni–B–Mo, and Ni–B–W coatings are deposited; and their tribological behavior at room and high temperatures are investigated. Electroless Ni–B, Ni–B–Mo, and Ni–B–W coatings are deposited on AISI 1040 steel substrates. The coatings are heat treated to improve their mechanical properties and crystallinity. Tribological behavior of the coatings is determined on a pin-on-disc type tribological test setup using various applied normal loads (10–50 N) and sliding speeds (0.25–0.42 m/s) to measure wear and coefficient of friction at different operating temperatures (25 °C–500 °C). Ni–B–W coatings are observed to have higher wear resistance than Ni–B or Ni–B–Mo coatings throughout the temperature range considered. Although for coefficient of friction, no such trend is observed. The worn surface of the coatings at 500 °C is characterized by lubricious oxide glazes, which lead to enhanced tribological behavior compared with that at 100 °C. A study of the coating characteristics such as composition, phase transformations, surface morphology, and microhardness is also carried out prior to tribological tests. Full article

(This article belongs to the Special Issue Tribological Challenges in Extreme Environments)

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13 pages, 8534 KiB

Open AccessArticle

Study of the Lubricating Ability of Protic Ionic Liquid on an Aluminum–Steel Contact

by Akshar Patel, Hong Guo and Patricia Iglesias^*

Kate Gleason College of Engineering, Rochester Institute of Technology, Rochester, NY 14623, USA

Lubricants 2018, 6(3), 66; https://doi.org/10.3390/lubricants6030066 - 28 Jul 2018

Cited by 25 | Viewed by 7244

Abstract

Contact friction between moving components leads to severe wear and failure of engineering parts, resulting in large economic losses. The lubricating ability of the protic ionic liquid, tri-[bis(2-hydroxyethylammonium)] citrate (DCi), was studied as a neat lubricant and as an additive in a mineral [...] Read more.

Contact friction between moving components leads to severe wear and failure of engineering parts, resulting in large economic losses. The lubricating ability of the protic ionic liquid, tri-[bis(2-hydroxyethylammonium)] citrate (DCi), was studied as a neat lubricant and as an additive in a mineral oil (MO) at various sliding velocities and constant load on an aluminum–steel contact using a pin-on-disk tribometer. Tribological tests were also performed at different concentrations of DCi. When DCi was used as an additive in MO, friction coefficient and wear volume were reduced for each sliding velocity, with a maximum friction and wear reduction of 16% and 40%, respectively, when 2 wt % DCi was added to MO at a sliding velocity of 0.15 m/s. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were also applied to analyze the wear mechanism of the interface lubricated by MO and DCi as additive. Full article

(This article belongs to the Special Issue Ionic Liquids: Friction and Lubrication Mechanisms)

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25 pages, 20613 KiB

Open AccessArticle

Evaluation of Wear Phenomena of Journal Bearings by Close to Component Testing and Application of a Numerical Wear Assessment

by Philipp Bergmann^*

, Florian Grün

, Florian Summer

and István Gódor

Department Product Engineering, Chair of Mechanical Engineering, Montanuniversität Leoben, Franz-Josef-Straße 18, 8700 Leoben, Austria

Lubricants 2018, 6(3), 65; https://doi.org/10.3390/lubricants6030065 - 26 Jul 2018

Cited by 12 | Viewed by 6742

Abstract

Hydrodynamic journal bearings are subjected to progressively rough loading conditions leading to an increased share of operation in mixed and boundary lubrication. This results in increased frictional losses, additional wear and a higher chance of failure, which calls for the understanding of wear [...] Read more.

Hydrodynamic journal bearings are subjected to progressively rough loading conditions leading to an increased share of operation in mixed and boundary lubrication. This results in increased frictional losses, additional wear and a higher chance of failure, which calls for the understanding of wear processes and the necessity of a numerical assessment. We conducted wear investigations of journal bearings by making use of a close-to-component test setting, and the progress of wear could be linked to the introduced frictional energy and in combination with a comprehensive surface analysis tribological effects could be resolved in detail. Achieved wear coefficients were implemented in a novelly developed numerical framework, which allows for the dynamic numerical evaluation of operation in the fluid and mixed lubrication regime and simultaneously occurring wear processes. By comparing numerical and experimental results, we evaluated the numerical framework’s capability to conduct holistic simulations including aspects like dynamically changing operation conditions, fluid and mixed lubrication as well as wear. Full article

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18 pages, 3364 KiB

Open AccessArticle

Molecular Mechanisms Underlying Lubrication by Ionic Liquids: Activated Slip and Flow

by Mengwei Han and Rosa M. Espinosa-Marzal^*

University of Illinois at Urbana-Champaign, 205 N Matthews Avenue, Urbana, IL 61801, USA

Lubricants 2018, 6(3), 64; https://doi.org/10.3390/lubricants6030064 - 20 Jul 2018

Cited by 24 | Viewed by 5249

Abstract

The present study provides molecular insight into the mechanisms underlying energy dissipation and lubrication of a smooth contact lubricated by an ionic liquid. We have performed normal and lateral force measurements with a surface forces apparatus and by colloidal probe atomic force microscopy [...] Read more.

The present study provides molecular insight into the mechanisms underlying energy dissipation and lubrication of a smooth contact lubricated by an ionic liquid. We have performed normal and lateral force measurements with a surface forces apparatus and by colloidal probe atomic force microscopy on the following model systems: 1-ethyl-3-methyl imidazolium bis-(trifluoro-methylsulfonyl) imide, in dry state and in equilibrium with ambient (humid) air; the surface was either bare mica or functionalized with a polymer brush. The velocity-dependence of the friction force reveals two different regimes of lubrication, boundary-film lubrication, with distinct characteristics for each model system, and fluid-film lubrication above a transition velocity

V^{*}

. The underlying mechanisms of energy dissipation are evaluated with molecular models for stress-activated slip and flow, respectively. The stress-activated slip assumes that two boundary layers (composed of ions/water strongly adsorbed to the surface) slide past each other; the dynamics of interionic interactions at the slip plane and the strength of the interaction dictate the change in friction -decreasing, increasing or remaining constant- with velocity in the boundary-film lubrication regime. Above a transition velocity

V^{*}

, friction monotonically increases with velocity in the three model systems. Here, multiple layers of ions slide past each other (“flow”) under a shear stress and friction depends on a shear-activation volume that is significantly affected by confinement. The proposed friction model provides a molecular perspective of the lubrication of smooth contacts by ionic liquids and allows identifying the physical parameters that control friction. Full article

(This article belongs to the Special Issue Ionic Liquids: Friction and Lubrication Mechanisms)

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11 pages, 4679 KiB

Open AccessArticle

Lubrication Performance of α-Zirconium Phosphates as an Anti-Wear Additive in Vegetable Oil-Based Anhydrous Calcium Grease

by Yingjing Dai, Hong Xu^* and Jinxiang Dong^*

College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, China

Lubricants 2018, 6(3), 63; https://doi.org/10.3390/lubricants6030063 - 18 Jul 2018

Cited by 10 | Viewed by 4432

Abstract

Vegetable oil has significant potential as a base oil, and substitute for mineral oil in grease formulation due to its biodegradability, low toxicity and excellent lubrication. This paper studied the development of vegetable oil-based greases with α-Zr(HPO₄)₂·H₂O [...] Read more.

Vegetable oil has significant potential as a base oil, and substitute for mineral oil in grease formulation due to its biodegradability, low toxicity and excellent lubrication. This paper studied the development of vegetable oil-based greases with α-Zr(HPO₄)₂·H₂O (α-ZrP) as an additive, exploring base oil influence in tribological behavior. The results demonstrated that the addition of α-ZrP in vegetable-based greases is beneficial to anti-wear property. α-ZrP particles exhibit good performance in anti-wear, friction-reduction and load-carrying capacity, and its tribological performances are better than the normally used molybdenum disulfide and graphite additives. Owing to its superior tribological properties as a vegetable oil-based grease additive, α-ZrP holds great potential for use in environmentally friendly applications in the future. Full article

(This article belongs to the Special Issue Wear Resistant Materials)

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10 pages, 2397 KiB

Open AccessArticle

Effect of Low Depth Surface Texturing on Friction Reduction in Lubricated Sliding Contact

by Haytam Kasem^1,2,*, Ori Stav¹, Philipp Grützmacher³

and Carsten Gachot⁴

¹ Department of Mechanical Engineering, Technion, Haifa 32000, Israel

² Department of Mechanical Engineering, Azrieli College of Engineering, Jerusalem 9103501, Israel

³ Department of Materials Science and Engineering, Functional Materials, Saarland University, Saarbrücken 66123, Germany

⁴ Institute for Engineering Design and Logistics Engineering E307-3, Vienna University of Technology, Vienna 1060, Austria

Lubricants 2018, 6(3), 62; https://doi.org/10.3390/lubricants6030062 - 17 Jul 2018

Cited by 42 | Viewed by 6106

Abstract

Laser surface texturing is an interesting possibility to tailor materials’ surfaces and thus to improve the friction and wear properties if proper texture feature sizes are selected. In this research work, stainless steel surfaces were laser textured by two different laser techniques, i.e., [...] Read more.

Laser surface texturing is an interesting possibility to tailor materials’ surfaces and thus to improve the friction and wear properties if proper texture feature sizes are selected. In this research work, stainless steel surfaces were laser textured by two different laser techniques, i.e., the direct laser interference patterning by using a nanosecond pulsed Nd:YAG laser and additionally by an ultrashort pulsed femtosecond Ti:Sa. The as-textured surfaces were then studied regarding their frictional response in a specially designed linear reciprocating test rig under lubricated conditions with a fully formulated 15W40 oil. Results show that dimples with smaller diameter lead to a significant reduction in the coefficient of friction compared to the dimples with a larger diameter and surfaces with a grid-like surface pattern produced by direct laser interference patterning. Full article

(This article belongs to the Special Issue Improvement of Friction and Wear by Laser Surface Texturing)

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19 pages, 5898 KiB

Open AccessArticle

The Influence of Surface Texturing on the Film Thickness in Starved Lubricated Parallel Sliding Contacts

by Dariush Bijani^1,*

, Elena L. Deladi², Matthijn B. De Rooij³ and Dirk J. Schipper³

¹ Materials Innovation Institute (M2i), P.O. Box 5008, 2600 GA Delft, The Netherland

² Bosch Transmission Technology, Dr. Hub Van Doorneweg 120, 5026 RA Tilburg, The Netherlands

³ Laboratory for Surface Technology and Tribology, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands

Lubricants 2018, 6(3), 61; https://doi.org/10.3390/lubricants6030061 - 11 Jul 2018

Cited by 9 | Viewed by 4384

Abstract

In industrial applications, a starved lubrication condition may occur, leading to a reduction in film thickness; by modifying the surface geometry, the tribological performance of the contact is enhanced. In this paper, the influence of surface texturing as a method for reducing the [...] Read more.

In industrial applications, a starved lubrication condition may occur, leading to a reduction in film thickness; by modifying the surface geometry, the tribological performance of the contact is enhanced. In this paper, the influence of surface texturing as a method for reducing the friction on the film thickness in parallel sliding surfaces for starved lubricated contacts is investigated. The results in this study have shown that surface texturing can improve film formation for starved lubricated contacts and, respectively, the load carrying capacity. The effect of starvation on several texturing patterns with several texturing properties was investigated and the film thickness for these conditions was studied. With the numerical algorithm developed and taking cavitation into consideration, the effect of shape, depth, size, and texture pitch on the film thickness was studied. Full article

(This article belongs to the Special Issue Tribological Performance of Textured Surfaces)

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9 pages, 2370 KiB

Open AccessArticle

Tribology of Wire Arc Spray Coatings under the Influence of Regenerative Fuels

by Roman Böttcher¹, Hans-Jörg Winkler¹, Martin Dienwiebel^1,2

and Matthias Scherge^1,*

¹ Fraunhofer IWM MikroTribologie Centrum, Rintheimer Querallee 2a, 76131 Karlsruhe, Germany

² Karlsruhe Institute of Technology, Institute for Applied Materials IAM, Strasse am Forum 7, 76131 Karlsruhe, Germany

Lubricants 2018, 6(3), 60; https://doi.org/10.3390/lubricants6030060 - 9 Jul 2018

Cited by 2 | Viewed by 4226

Abstract

In order to further optimize the efficiency of today’s internal combustion engines, specific coatings are used on functional surfaces to reduce internal engine friction and wear. In the current research project, oxymethylene ether (OME) is discussed because it is CO₂ neutral and [...] Read more.

In order to further optimize the efficiency of today’s internal combustion engines, specific coatings are used on functional surfaces to reduce internal engine friction and wear. In the current research project, oxymethylene ether (OME) is discussed because it is CO₂ neutral and has a strong soot-reducing effect as a fuel or fuel additive. In some operational regimes of the internal combustion engine a dilution of engine oil by fuel must be assumed. In this paper, the frictional contact between piston ring and cylinder raceway is modelled using a pin-on-disk tribometer and the friction and wear behavior between a diamond-like carbon coating (DLC) and a thermal spray coating is characterized. The wear of the spray layer could be continuously detected by radionuclide technology (RNT). With the aid of photoelectron spectroscopic measurements (XPS), the steel thermal spray coating was chemically analyzed before and after the tribometer tests and the oxidative influence of OME was investigated. In addition, confocal microscopy was used to assess the topographies of the specimens. The measurements showed that the addition of OME to the lubricant reduced the viscosity and load-bearing capacity of the lubricating film, which led to an increase in the coefficient of friction. While almost no wear on the pin could be detected at 10% OME, the first visible material removal occurs at an OME content of 20% and the layer delaminated at 30% OME. The evaluation of the RNT wear tests showed that both the tests with engine oil and with engine oil plus 20% OME achieved very low wear rates. No corrosion of the thermal spray coating could be detected by XPS. Only the proportion of engine oil additives in the friction track increased with increasing OME concentration. Full article

(This article belongs to the Special Issue Applied Nanotribology)

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14 pages, 5096 KiB

Open AccessArticle

Ultra-Low Friction on Tetrahedral Amorphous Diamond-Like Carbon (ta-C) Lubricated with Ethylene Glycol

by Svenja Bachmann¹, Marcus Schulze^1,2, Lisa Krell³, Rolf Merz⁴, Michael Wahl⁴ and Robert W. Stark^1,2,*

¹ Physics of Surfaces, Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 16, D-64287 Darmstadt, Germany

² Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Str. 10, D-64287 Darmstadt, Germany

³ BMW Group, D-80788 Munich, Germany

⁴ Institute for Surface and Thin Film Analysis (IFOS), Trippstadter Straße 120, D-67663 Kaiserslautern, Germany

Lubricants 2018, 6(3), 59; https://doi.org/10.3390/lubricants6030059 - 7 Jul 2018

Cited by 8 | Viewed by 7277

Abstract

Lubricated tetrahedral amorphous carbon coatings can show a very complex tribological behavior. In particular, friction regimes with extremely low friction have been observed. In tribological experiments with a ta-C/steel friction pair that was lubricated with ethylene glycol, we observed a sudden and very [...] Read more.

Lubricated tetrahedral amorphous carbon coatings can show a very complex tribological behavior. In particular, friction regimes with extremely low friction have been observed. In tribological experiments with a ta-C/steel friction pair that was lubricated with ethylene glycol, we observed a sudden and very strong decrease in the effective friction coefficient from 0.45 to 0.01 after running-in. By varying different components of the tribological system after this abrupt decrease we investigated the role of the counter-body, the lubricant and the coating. To investigate the surface chemistry, static time-of-flight secondary ion mass spectrometry (ToF-SIMS), dynamic secondary ion mass spectrometry (SIMS), and X-ray photoelectron spectroscopy (XPS) measurements were performed. Using deuterated lubricants, ToF-SIMS measurements allowed us to distinguish adsorption of hydrogen and hydroxyl-groups from the lubricant from the adsorption from the environment. Deuterated hydroxyl-groups from the lubricant adsorbed to the surface during the experiment. In particular, more adsorbed deuterated hydroxyl-groups were detected prior to the sudden decrease in the friction coefficient. Thus, the sudden decrease in the coefficient of friction was most likely caused by an interplay between the lubricant, the ta-C coating and the counter-body which lead to the formation of transfer and adsorption layers. Full article

(This article belongs to the Special Issue Applied Nanotribology)

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19 pages, 7606 KiB

Open AccessReview

Electron Microscopy and Spectroscopy in the Analysis of Friction and Wear Mechanisms

by Quanshun Luo

Materials and Engineering Research Institute, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK

Lubricants 2018, 6(3), 58; https://doi.org/10.3390/lubricants6030058 - 4 Jul 2018

Cited by 21 | Viewed by 8619

Abstract

Friction and wear take place on two solid surfaces in sliding contact as a result of the mechanical, thermal, and chemical interactions with the participation of environmental species. These interactions lead to the formation of a tribo-layer or tribofilm, which attaches on the [...] Read more.

Friction and wear take place on two solid surfaces in sliding contact as a result of the mechanical, thermal, and chemical interactions with the participation of environmental species. These interactions lead to the formation of a tribo-layer or tribofilm, which attaches on the worn surfaces, and consequently, contributes to the variation of the friction and wear behaviour. Electron microscopy and the associated spectroscopic analyses are powerful in probing these matters in spatial resolutions from micro to atomic scale. This article provides a review of the author’s work in the wear and friction mechanisms of physical vapour deposition (PVD) hard coatings, in which various scanning electron microscope (SEM)- and transmission electron microscope (TEM)-based microscopic and spectroscopic techniques were employed. Understanding on the failure mechanisms and the origin of self-adaptive friction has been improved to the nano-scale. Other related issues are also discussed, such as sample preparation techniques for cross-sectional electron microscopy, energy dispersive X-ray spectroscopy, and electron energy loss spectroscopy. Full article

(This article belongs to the Special Issue Tribology in Metal Forming)

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15 pages, 6360 KiB

Open AccessArticle

Performance Evaluation and Lubrication Mechanism of Water-Based Nanolubricants Containing Nano-TiO₂ in Hot Steel Rolling

by Hui Wu¹

, Jingwei Zhao¹, Liang Luo², Shuiquan Huang³

, Lianzhou Wang⁴, Suoquan Zhang⁵, Sihai Jiao⁵, Han Huang^3,* and Zhengyi Jiang^1,*

¹ School of Mechanical, Materials, Mechatronic and Biomedical Engineering, University of Wollongong, Wollongong, NSW 2522, Australia

² Automotive Research Institute, Hefei University of Technology, Hefei 230009, China

³ School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, QLD 4072, Australia

⁴ School of Chemical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia

⁵ Baosteel Research Institute (R&D Centre), Baoshan Iron & Steel Co., Ltd., Shanghai 200431, China

Lubricants 2018, 6(3), 57; https://doi.org/10.3390/lubricants6030057 - 2 Jul 2018

Cited by 33 | Viewed by 9118

Abstract

Hot rolling tests of a low-alloy steel were conducted at a rolling temperature of 850 °C under different lubrication conditions, including benchmarks (dry condition and water) and water-based nanolubricants containing different concentrations of nano-TiO₂ from 1.0 to 8.0 wt%. The effects of [...] Read more.

Hot rolling tests of a low-alloy steel were conducted at a rolling temperature of 850 °C under different lubrication conditions, including benchmarks (dry condition and water) and water-based nanolubricants containing different concentrations of nano-TiO₂ from 1.0 to 8.0 wt%. The effects of nanolubricants on rolling force, surface roughness, thickness of oxide scale, and microstructure were systematically investigated through varying nano-TiO₂ concentrations. The results show that the application of nanolubricants can decrease the rolling force, surface roughness and oxide scale thickness of rolled steels, and refine ferrite grains. In particular, the nanolubricant containing an optimal concentration (4.0 wt%) of nano-TiO₂ demonstrates the best lubrication performance, owing to the synergistic effect of lubricating film, rolling, polishing, and mending generated by nano-TiO₂. Full article

(This article belongs to the Special Issue Tribology in Metal Forming)

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Lubricants, Volume 6, Issue 3 (September 2018) – 28 articles

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