Special Issue "Improvement of Friction and Wear by Laser Surface Texturing"

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

Deadline for manuscript submissions: closed (31 July 2017).

Special Issue Editors

Dr. Andreas Rosenkranz
E-Mail Website
Guest Editor
Center for Magnetic Memory and Recording, University of California, San Diego, UCSD, USA
Interests: surface texturing, friction and wear mechanisms; lubrication regime; nano-scale materials characterization; nano-additives
Prof. Dr. Carsten Gachot
E-Mail Website
Guest Editor
Technische Universität Wien, Vienna, Austria
Interests: tribofilm formation in machine elements; materials tribology; surface engineering; wear processes; contact mechanics at different length scales
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Special Issue Information

Dear Colleagues,

Although it started some decades ago, surface texturing, as a means to overcome the stochastic surface roughness of materials by creating well-defined surface topographies, is still a fascinating and growing research field. A number of advances have been made in improving surface texturing techniques and analytical methods. In particular, the development of new powerful laser sources with shorter pulse durations down to femtoseconds caused a great sensation, as laser are flexible and universal texturing tools, which can be used for almost all kind of materials. Many research articles have already been published dealing with effects of surface textures under different sliding and lubrication conditions. Especially under hydrodynamic and elasto-hydrodynamic lubrication, numerous papers appeared addressing these issues and the underlying mechanisms in those regimes can be considered as well-understood. Additionally, increasing progress in modeling and computation shed more light on the mechanisms in abovementioned lubrication regimes.

Nowadays, most machine elements operate in different lubrication regimes in one duty cycle due to start-stop processes for example. It is, therefore, highly necessary to take boundary, mixed and even dry contacts under consideration. This is exactly the point where most conflicting reports arise since the fundamental mechanisms are still not fully understood in this highly dynamic and exciting research area.

This Special Issue exclusively aims at the latest developments in the field of laser surface texturing under dry, boundary and finally mixed contacts. Hydrodynamic and elasto-hydrodynamic lubrication should not be considered here. Research articles dedicated to improvements in the accuracy and processing speeds of laser surface texturing techniques, addressing fundamental relationships between the as-produced textures and the respective frictional regimes, as well as the resulting wear behavior, will be of great interest to this Special Issue. Advances in modeling and the cross-correlation to experimental findings in those lubrication regimes are also highly welcome.

Dr. Andreas Rosenkranz
Prof. Dr. Carsten Gachot
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 papers will be 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 1000 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

  • Laser surface texturing
  • dry contacts
  • boundary lubrication
  • mixed lubrication
  • modelling

Published Papers (10 papers)

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Research

Open AccessArticle
Effect of Low Depth Surface Texturing on Friction Reduction in Lubricated Sliding Contact
Lubricants 2018, 6(3), 62; https://doi.org/10.3390/lubricants6030062 - 17 Jul 2018
Cited by 5
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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Open AccessArticle
Laser Surface Texturing of TiAl Multilayer Films—Effects of Microstructure and Topography on Friction and Wear
Lubricants 2018, 6(2), 36; https://doi.org/10.3390/lubricants6020036 - 16 Apr 2018
Cited by 4
Abstract
Laser surface texturing is an efficient way to control the friction and wear properties of materials. Although described in many papers, most previous work relates to a pure topographic view of laser-textured surfaces. As lasers are heat sources, their thermal impact during treatment [...] Read more.
Laser surface texturing is an efficient way to control the friction and wear properties of materials. Although described in many papers, most previous work relates to a pure topographic view of laser-textured surfaces. As lasers are heat sources, their thermal impact during treatment can be high enough to modify the material’s microstructure or surface chemistry and affect tribological properties as well. This research took a closer look at the microstructure of laser-textured TiAl multilayers, besides topographic aspects. Direct laser interference patterning was used to create well-defined line-like surface textures in TiAl multilayers with differing lateral feature sizes in the micron range. High-resolution techniques such as TEM and XRD highlighted the effect of this method on microstructure, and in particular, the phase situation of the TiAl multilayer. Thermal simulations demonstrated that the maximum achievable temperatures were around 2000 K, thus being high enough to melt Ti and Al. Cooling rates on the order of 109 K/s depended on the lateral feature size, potentially leading to metastable microstructures. Finally, ball-on-disk tests on as-textured TiAl specimens showed a reduction in wear under dry conditions depending on the periodicity of the line-like textures used. Full article
(This article belongs to the Special Issue Improvement of Friction and Wear by Laser Surface Texturing)
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Open AccessCommunication
Facilitating the Study of the Texturing Effect on Hydrodynamic Lubrication
Lubricants 2018, 6(1), 18; https://doi.org/10.3390/lubricants6010018 - 11 Feb 2018
Abstract
To facilitate fundamental study of the surface texturing effect on hydrodynamic lubrication, analytical and experimental tools are required. While there is an extensive amount of theoretical and analytical analyses in the literature, relevant experimental studies are much rarer. A detailed study requires techniques [...] Read more.
To facilitate fundamental study of the surface texturing effect on hydrodynamic lubrication, analytical and experimental tools are required. While there is an extensive amount of theoretical and analytical analyses in the literature, relevant experimental studies are much rarer. A detailed study requires techniques by which one can (a) produce micron-sized textures on a millimeter-scale area on a specimen surface and (b) accurately measure the lubricating film thickness and load-carrying capacity of a bearing. The paper introduces the use of an efficient laser technique (direct laser interference patterning) and a custom-designed fixed-incline slider tester to address these points. A steel slider was textured with the laser technique to produce a surface pattern in the inlet region of the bearing contact. The characterization of the load-carrying capacity for different convergence ratios K is presented. Full article
(This article belongs to the Special Issue Improvement of Friction and Wear by Laser Surface Texturing)
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Open AccessArticle
Effect of Surface Texturing on Cast Iron Reciprocating against Steel under Cyclic Loading in Boundary and Mixed Lubrication Conditions
Lubricants 2018, 6(1), 2; https://doi.org/10.3390/lubricants6010002 - 02 Jan 2018
Cited by 1
Abstract
This study investigates the effect of laser surface texturing on the friction behavior of grey cast iron reciprocating under boundary, mixed lubrication conditions and cyclic loading. Four geometrical parameters of micro-textures (feature depth, feature diameter, area fraction, and sliding direction) were studied using [...] Read more.
This study investigates the effect of laser surface texturing on the friction behavior of grey cast iron reciprocating under boundary, mixed lubrication conditions and cyclic loading. Four geometrical parameters of micro-textures (feature depth, feature diameter, area fraction, and sliding direction) were studied using a design of experiments (DoE) approach. The results showed that depending on the geometry, micro-textures can have either a positive or a negative effect on the friction behavior. The DoE analysis revealed that the coefficient of friction is mainly affected by the interaction of the feature depth and its diameter. It was found that this can be related to the aspect ratio of the dimples, and the best results were obtained for an aspect ratio of 0.1 and 0.17. Full article
(This article belongs to the Special Issue Improvement of Friction and Wear by Laser Surface Texturing)
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Open AccessArticle
Reduction of the Adhesive Friction of Elastomers through Laser Texturing of Injection Molds
Lubricants 2017, 5(4), 45; https://doi.org/10.3390/lubricants5040045 - 16 Nov 2017
Cited by 3
Abstract
It is well known that elastomers usually possess poor dry sliding friction properties due to their highly adhesive character. In order to overcome this problematic behavior in industrial applications, interfacial materials such as oils, greases, coatings, or lacks are normally used in order [...] Read more.
It is well known that elastomers usually possess poor dry sliding friction properties due to their highly adhesive character. In order to overcome this problematic behavior in industrial applications, interfacial materials such as oils, greases, coatings, or lacks are normally used in order to separate or to functionalize the contact surfaces of elastomers. Alternatively, the high adhesion tendency of elastomers may be explicitly reduced by modifying the elastomer composition itself or by enabling a reduction of its effective contact area through, for example, surface laser texturing. This second approach, i.e., the reduction of the adhesive character of elastomers through laser structuring, will be the main topic of the present study. For this purpose, different micro-sized grooved structures were produced on flat injection molds using an ultra-short pulsed laser. The micro-structured molds were then used to produce injection molded micro-ridged Liquid Silicone Rubber (LSR) sample pads. The investigations consisted firstly of determining the degree of replication of the mold micro-structures onto the surface of the LSR pads and secondly, to ascertain the degree of reduction of the friction force (or coefficient of friction) of these micro-ridged LSR pads in comparison to the benchmark (unstructured LSR pads) when tested under dry conditions against Aluminum alloy (Al-6082) or PA6.6-GF30 plates. For this second part of the investigation, the normal force (or contact pressure) dependency of the coefficient of friction was determined through stepwise load increasing friction tests. The results of these investigations have shown that the production of micro-ridged surfaces on LSR pads through laser structuring of the injection molds could be successfully achieved and that it enables a significant reduction of the friction force for low normal forces (or contact pressures), where the component of adhesion friction is playing an important and determining role in the overall friction behavior of the LSR elastomer. Full article
(This article belongs to the Special Issue Improvement of Friction and Wear by Laser Surface Texturing)
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Open AccessArticle
Non-Uniform Laser Surface Texturing of an Un-Tapered Square Pad for Tribological Applications
Lubricants 2017, 5(4), 41; https://doi.org/10.3390/lubricants5040041 - 17 Oct 2017
Cited by 2
Abstract
Femtosecond laser surface micro-texturing has emerged as a promising technology to enhance the tribological properties of different kinds of electromechanical devices. In this research paper, we have exploited the intrinsic flexibility and micrometric accuracy of femtosecond laser ablation to realize complex micro-structural modifications [...] Read more.
Femtosecond laser surface micro-texturing has emerged as a promising technology to enhance the tribological properties of different kinds of electromechanical devices. In this research paper, we have exploited the intrinsic flexibility and micrometric accuracy of femtosecond laser ablation to realize complex micro-structural modifications on the surface of a laboratory prototype of a steel thrust bearing (un-tapered) pad. The Bruggeman Texture Hydrodynamics theory (BTH) is employed for the design of the anisotropic and non-uniform texture maximizing the thrust load of the pad prototype. The preliminary experimental results, reported in this work, show that the non-uniform micro-texture largely affects the friction characteristics of the contact. In particular, in agreement with the BTH predictions, the tribo-system shows friction properties that are strongly sensitive to the direction of the sliding speed, as a consequence of the micro-fluid dynamics which are designed to occur only in a specific sliding direction. We suggest that the joint action of virtual prototyping (BTH lubrication theory) and ultrafast laser micro-prototyping can lead to unconventional and impressive results in terms of enhanced or tailored contact mechanics properties of the generic lubricated tribopair. Full article
(This article belongs to the Special Issue Improvement of Friction and Wear by Laser Surface Texturing)
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Open AccessArticle
Enhanced Growth of ZDDP-Based Tribofilms on Laser-Interference Patterned Cylinder Roller Bearings
Lubricants 2017, 5(4), 39; https://doi.org/10.3390/lubricants5040039 - 25 Sep 2017
Cited by 7
Abstract
Laser surface texturing has been successfully applied in the past to various machine elements in order to improve their tribological performance. In this study, direct laser interference patterning was used to produce periodic cross-like surface patterns on commercial cylinder roller bearings. The wear [...] Read more.
Laser surface texturing has been successfully applied in the past to various machine elements in order to improve their tribological performance. In this study, direct laser interference patterning was used to produce periodic cross-like surface patterns on commercial cylinder roller bearings. The wear behavior of as-patterned bearings was studied by a modified FE8 test rig under boundary lubrication. A mineral oil (ISO VG 100) as a base oil additivated with 0.02 wt % zinc dialkyldithiophosphate (ZDDP) was used for the tribological tests which were performed under a Hertzian pressure of 1.92 GPa and maintained at 80 °C and 20 rpm for 2 h. The laser-patterned bearings showed a significantly reduced mass loss by two orders of magnitude compared to the unpatterned reference bearings. A closer look at the samples proved the formation of the characteristic blue-colored ZDDP tribofilm on top of the laser-induced topography maximum positions. Due to the higher contact pressure at the laser-induced peaks, the tribofilm formation was preferable at those positions thus protecting against wear. The laser patterns nearly remained unworn compared to the reference samples. A subsequent Raman analysis of the laser-patterned bearings clearly revealed the formation of zinc and iron sulfides as well as phosphates at the peak points. Full article
(This article belongs to the Special Issue Improvement of Friction and Wear by Laser Surface Texturing)
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Open AccessArticle
Low Friction and High Solid-Solid Contact Ratio—A Contradiction for Laser-Patterned Surfaces?
Lubricants 2017, 5(3), 35; https://doi.org/10.3390/lubricants5030035 - 26 Aug 2017
Cited by 1
Abstract
Recording of Stribeck-like curves is a common way to study the effect of laser-patterned surfaces on the frictional efficiency. However, solely relying on the coefficient of friction when identifying the lubrication regime and the underlying working principles can be misleading. Consequently, a ball-on-disc [...] Read more.
Recording of Stribeck-like curves is a common way to study the effect of laser-patterned surfaces on the frictional efficiency. However, solely relying on the coefficient of friction when identifying the lubrication regime and the underlying working principles can be misleading. Consequently, a ball-on-disc tribometer was combined with an electrical resistivity circuit to simultaneously measure Stribeck-like curves and solid-solid contact ratios for polished and laser-patterned samples. Line-like surface patterns with different periodicities were produced by direct laser interference patterning on steel substrates (AISI304). The reference shows a Stribeck-like behavior well correlating with the contact ratios. The behavior deviates for high sliding velocities (high contact ratios) due to a loss of lubricant induced by centrifugal forces pulling the lubricant out of the contact zone. In contrast, the solid–solid contact ratio of the laser-patterned samples is around 80% for all sliding velocities. Those values can be explained by higher contact pressures and the structural depth induced by the surface topography which make a full separation of the surfaces unlikely. Despite those high values for the contact ratio, laser-patterning significantly reduces friction, which can be traced back to a reduced real contact area and the ability to store oil in the contact zone. Full article
(This article belongs to the Special Issue Improvement of Friction and Wear by Laser Surface Texturing)
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Open AccessArticle
Laser Textured Surfaces for Mixed Lubrication: Influence of Aspect Ratio, Textured Area and Dimple Arrangement
Lubricants 2017, 5(3), 32; https://doi.org/10.3390/lubricants5030032 - 10 Aug 2017
Cited by 13
Abstract
Unidirectional sliding experiments with polished and laser textured steel surfaces were carried out to investigate the effects of different textured area densities, aspect ratios and dimple arrangements. The system was lubricated with Polyalphaolefin (PAO) at 100 °C and the contact pressure was 3 [...] Read more.
Unidirectional sliding experiments with polished and laser textured steel surfaces were carried out to investigate the effects of different textured area densities, aspect ratios and dimple arrangements. The system was lubricated with Polyalphaolefin (PAO) at 100 °C and the contact pressure was 3 MPa. For measuring Stribeck curves, the sliding speed was controlled between 40 and 2000 mm/s. The textured area density was varied between 5% and 30%, with the lowest friction values found for 10%. Aspect ratios ranging from 0.02 to 0.2 were investigated and for 0.1 the lowest friction values were measured. The dimple arrangements tested were cubic, hexagonal and a random distribution for a textured area density of 10% and an aspect ratio of 0.1. Our results demonstrate that the dimple arrangement does affect friction values, hinting to the fact that individual texture elements do influence each other. The optimum dimple arrangement was found in a hexagonal packing. This systematic variation of these three key texturing parameters for the morphological texturing of a tribological surface with dimples will allow a strategic choice of texturing parameters. This makes the most of the tremendous potential that laser surface texturing has for reducing friction forces and thereby CO2 emissions. Full article
(This article belongs to the Special Issue Improvement of Friction and Wear by Laser Surface Texturing)
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Open AccessArticle
Wear Characterization of Cemented Carbides (WC–CoNi) Processed by Laser Surface Texturing under Abrasive Machining Conditions
Lubricants 2017, 5(3), 20; https://doi.org/10.3390/lubricants5030020 - 22 Jun 2017
Cited by 7
Abstract
Cemented carbides are outstanding engineering materials widely used in quite demanding material removal applications. In this study, laser surface texturing is implemented for enhancing, at the surface level, the intrinsic bulk-like tribological performance of these materials. In this regard, hexagonal pyramids patterned on [...] Read more.
Cemented carbides are outstanding engineering materials widely used in quite demanding material removal applications. In this study, laser surface texturing is implemented for enhancing, at the surface level, the intrinsic bulk-like tribological performance of these materials. In this regard, hexagonal pyramids patterned on the cutting surface of a tungsten cemented carbide grade (WC–CoNi) have been successfully introduced by means of laser surface texturing. It simulates the surface topography of conventional honing stones for abrasive application. The laser-produced structure has been tested under abrasive machining conditions with full lubrication. Wear of the structure has been characterized and compared, before and after the abrasive machining test, in terms of changes in geometry aspect and surface integrity. It is found that surface roughness of the machined workpiece was improved by the laser-produced structure. Wear characterization shows that laser treatment did not induce any significant damage to the cemented carbide. During the abrasive machining test, the structure exhibited a high wear resistance. Damage features were only discerned at the contacting surface, whereas geometrical shape of pyramids remained unchanged. Full article
(This article belongs to the Special Issue Improvement of Friction and Wear by Laser Surface Texturing)
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