Article

Laser surface texturing for adaptive solid lubrication

December 2006
Wear 261(11):1285-1292

December 2006
261(11):1285-1292

DOI:10.1016/j.wear.2006.03.013

Authors:

Andrey A Voevodin

University of North Texas

Jeffrey Zabinski

US Army

Solid lubricant systems were developed to provide friction and wear reduction in variable environmental conditions. The mechanisms employed to achieve cross-environment capability include “on demand” solid lubricant supply from reservoirs in hard wear protective coatings. This research explores recent advances in a precision laser machining to generate arrays of micrometer sized dimple reservoirs with controlled size, location, and density. These micro-reservoirs were machined by a focused UV laser beam on the surface of hard TiCN coatings produced by a cathodic vacuum arc deposition. Different dimple diameters and spacing were used to achieve area coverage with micro-reservoirs between 0.5% and 50% of the entire tribological contact surface. Solid lubricants based on MoS2 and graphite were then applied by burnishing and sputtering to such laser textured surfaces. Sliding friction tests were performed against steel balls in humid air and dry nitrogen environments. The results indicate that there is an optimum dimple surface coverage of about 10%. The life of the solid lubricants on dimpled surfaces was an order of magnitude longer than on the unmodified TiCN coating surface. The laser-processed micro-reservoirs also helped to renew lubricant supply for tests with multiple cycling between humid air and dry nitrogen. Tribological surface adaptation to the test environment was investigated by micro-Raman, which demonstrated a repeated change from hexagonal MoS2 to graphite carbon in the wear track with each dry/humid environment cycle. Solid lubricant composition inside the micro-reservoirs did not change.

Numerische Auslegung von Oberflächenmikrotexturen für geschmierte tribologische Kontakte

Thesis

Full-text available

Jan 2021

Max Marian

Trotz einer Vielzahl an experimentellen und theoretischen Untersuchungen in der Literatur befindet sich der Ansatz der Oberflächenmikrotexturierung zur Steuerung von Reibung und Verschleiß in Tribo-Kontakten noch immer in der Trial-and-error-Phase. Ein ausbleibender Einzug in die industrielle Serienanwendung liegt insbesondere daran, dass der Einfluss auf das tribologische Verhalten und vorteilhafte Mikrotexturgeometrien und -anordnungen von der jeweiligen Kontaktart und den Betriebsbedingungen bedingt werden. Im Rahmen dieser Arbeit wurde daher eine Vorgehensweise zur Gestaltung von Oberflächenmikrotexturen erarbeitet. Den zentralen Kern bildeten dabei Simulationsmodelle zur numerischen Vorhersage des tribologischen Verhaltens von Mikrotexturen in geschmierten Kontakten basierend auf der Finite Elemente Methode. Die Möglichkeit zur maßgeschneiderten Auslegung der Mikrotexturgeometrie wurde durch ein Meta-Modell of Optimal Prognosis in Verbindung mit evolutionären Optimierungsalgorithmen geschaffen. Die Eignung und Validität wurde durch Anwendung für verschiedene hydrodynamische sowie harte und weiche elastohydrodynamische Kontakte von der Modell- bis hin zur Komponentenebene sowie durch begleitende experimentelle Untersuchungen aufgezeigt. Die Implementierung in kommerzieller Software sowie die Ableitung verallgemeinerter Gestaltungsrichtlinien erlauben zukünftig insbesondere die breite Nutzbarkeit durch Forschende und Entwicklungsingenieur*innen für verschiedene Anwendungen.

Synergetic Effects of Surface Texturing and Solid Lubricants to Tailor Friction and Wear - A Review

Article

Full-text available

Nov 2020
TRIBOL INT

Surface texturing and solid lubricants have demonstrated the ability to substantially reduce friction and wear under dry conditions. In recent decades, these two technologies have been combined to leverage the advantages of both for superior tribological performance. This review article first summarizes the state-of-the-art regarding surface texturing and solid lubricants, including soft metals, polytetrafluoroethylene, diamond-like carbon and 2D layered materials. Then, the synergy between surface textures and solid lubricants is discussed, with particular emphasis on the underlying mechanisms. Finally, gaps in the existing understanding of these synergies are identified and opportunities for future research are suggested.

Femtosecond laser texturing of DLC-based coatings by DLW method with sub-micrometer precision

Article

Full-text available

Aug 2022
INT J ADV MANUF TECH

Laser texturing of surfaces may provide specific functionality, such as altering hydrophobicity, changing optical properties, or reducing friction and wear. For the latter, surfaces of parts are often coated with protective and/or solid lubricant coating, and texturing may further improve the tribological properties in both dry or lubricated sliding. New laser technologies, such as the direct laser writing (DLW) method using a femtosecond laser, allow the production of extremely precise textures directly into the coating. Here, we describe a method of preparing ultra-precise textures into diamond-like carbon (DLC) coatings on a large area. The textured topography was assessed by 3D laser scanning microscope, which confirmed the repeatability of fs laser processing. Raman spectroscopy mapping, SEM, and XPS were combined to investigate the effect of laser processing on DLC coating in terms of oxidation or structural changes. Traditional process (i.e., coating textured surface) often results in coating adhesion/cohesion failure due to deposition of sharp edges produced by texturing, whereas our approach eliminates this issue. Even complex textures inside the coating are fabricated with a fast speed of 10 s per mm² and a high precision in texture depth (tens of nanometers), unlocking many application fields in tribology or microfluidics.

Surface Texturing in Cutting with Micro-Scale Structured Tools

Article

Full-text available

Feb 2022

Functional surfaces have been widely used for control of physical and/or chemical properties of substances on the surface. In the manufacturing industries, some of micro fabrication approaches such as laser processing have been applied to form textured surfaces, which control the surface functions with topographies. This study presents the surface texturing in cutting with micro-scale structured end mills. Micro-scale nicks are fabricated on the cutting edges of PCD (Poly-Crystalline Diamond) end mills in laser finishing. The cutting operation is conducted to form the chips on each nick with the cutter axis inclination in the feed direction. An analytical model is applied to control the surface structure for the spindle speed, the feed rate, the nick geometry and the inclination angle of the cutter axis. Then, the surface structures were fabricated in the actual cutting process. The machining operation in this study is available in fabrication of the micro-scale structures at high production rates and the structures shape can be controlled in the surface simulation.

Effective Application of Solid Lubricants in Spacecraft Mechanisms

Article

Full-text available

Jul 2020

Jeff Lince

Solid lubricants, antiwear coatings, and self-lubricating composites are used in applications on spacecraft where oils and greases cannot be used because of the need to avoid lubricant volatility/migration, and where the application requires significant temperature variation, accelerated testing, higher electrical conductivity, or operation in boundary conditions. The purpose of this review is to provide spacecraft designers with tools that can aid in the effective use of solid-based tribological materials, both to increase their usage, and to reduce anomalies. The various tribological material formulations are described, including how their materials, physical, and chemical properties affect their performance. Included are typical solid lubricants like PTFE and bonded or sputter-deposited MoS2, as well as low shear metal coatings, hard coatings, and composite materials (including bulk composites and nanocomposite coatings). Guidance is given on how to develop mechanisms that meet performance requirements, but also how to optimize robustness, so that success is achieved even under unforeseen circumstances. Examples of successful applications are given, as well as how to avoid potential pitfalls, and what the future of solid tribological materials may hold.

A Review of Surface Texturing in Internal Combustion Engine Piston Assembly

Article

Jun 2020

Laser-textured cross-hatched surface topography analysis with evaluation of high-frequency measurement noise

Article

Full-text available

Aug 2024
MEASUREMENT

Please cite this article as: P. Podulka, W. Macek, R. Branco, A. Kubit, Laser-textured cross-hatched surface topography analysis with evaluation of high-frequency measurement noise, Measurement (2024), doi: https:// Highlights • The surface topography of laser-textured cross-hatched materials was studied. • The results of roughness measurement using the contactless WLI method were analysed. • A procedure to mitigate the influence of high-frequency noise was proposed. • The noise was characterised by autocorrelation, power spectral, and direction functions. • The procedure was validated by studying the laser-texturing direction in profile data. Highlights • The surface topography of laser-textured cross-hatched materials was studied. • The results of roughness measurement using the contactless WLI method were analysed. • A procedure to mitigate the influence of high-frequency noise was proposed. • The noise was characterised by autocorrelation, power spectral, and direction functions. • The procedure was validated by studying the laser-texturing direction in profile data. Abstract: The precision of surface roughness determination using ISO 25178 parameters relies on various factors that directly impact the measurement process. In industry applications, the contactless roughness measurement reduces data collection time. However, it introduces several potential errors, including those stemming from the environment. One of the main types of errors encountered during topography analysis is measurement noise, which arises from different external disturbances. High-frequency noise is particularly studied as a result of vibration. In the present study, the laser-texture cross-hatched surface topographies were analysed using the results obtained from white light interference measurements. Measurement noise was defined based on noisy data, also called noise surface, which is the result of filter decomposition methods. This data separation technique was supported with power spectral analysis, autocorrelation function applications and texture direction characterisation. It was suggested to conduct a comprehensive study of the noisy data to enhance the understanding of texturing direction. Various data filtration techniques were studied, namely robust Gaussian, spline, fast Fourier transform and morphological closing-opening filters. The results of the proposed procedure were validated against variations in the values of ISO 25178 surface texture parameters. Validating the proposed approach, the variations of noise-sensitive surface texture parameters were compared to the variations of the same parameters but received by averaging three repeated measurements, as proposed by international standards. The main advantage of the proposed method against standards procedure was reducing the time of data collection when the measurement must be repeated and averaged. In conclusion, a method for reducing high-frequency measurement noise was introduced through the application of the proposed procedure.

Wear resistance of molybdenum disulfide-based coatings on titanium alloys: a review

Article

Full-text available

Mar 2024
J MATER SCI

With the rapid development of the global aerospace industry, higher requirements have been placed on the comprehensive performance of structural materials for aviation. Among them, titanium alloys are widely used in the design of rocket engine casings, rocket nozzle conduits and artificial satellite casings because of their high strength, good corrosion resistance and high heat resistance. However, the surface of titanium alloy has poor wear resistance, which makes it difficult to adapt to its practical use in the aviation environment, especially in high-temperature and wide-temperature conditions. Researchers have found that the preparation of molybdenum disulfide solid lubrication coatings on the surface of titanium alloys can significantly improve this problem. This review summarizes the research progress of MoS2-based material coatings, which contains the design of MoS2-based coating components, and the preparation methods of MoS2-based coatings. Therefore, the unitary, binary, diversified and multilayer designs of molybdenum disulfide-based materials in coatings are discussed. In addition, the current preparation methods of MoS2-based materials are reviewed, focusing on the improvement of wear resistance of titanium surfaces by MoS2–Ti coatings as well as plasma electrolytic oxidation (PEO) technology. Finally, the advantages and disadvantages of the current research on molybdenum disulfide-based materials are summarized, aiming to provide some references for the practical application of titanium alloys in the aerospace field. Graphical Abstract

Combining Carbon Nanoparticle Coatings and Laser Surface Texturing for Enhanced Lubricity Under High Loads

Article

Full-text available

Mar 2024
TRIBOL LETT

Developing new lubrication concepts greatly contributes to improving the energy efficiency of mechanical systems. Nanoparticles such as those based on carbon allotropes or 2D materials have received widespread attention due to their outstanding mechanical and tribological performance. However, these systems are limited by a short wear life. Combining nanoparticle coatings with laser surface texturing has been demonstrated to substantially improve their durability due to the reservoir effect which prevents immediate particle removal from the contact. In this study, we investigate the high-load (20 N) tribological performance of AISI 304 austenitic stainless-steel substrates, which are line-patterned by laser interference patterning and subsequently coated with different carbon nanoparticle coatings (carbon nanotubes, carbon onions, carbon nanohorns) against alumina and 100Cr6 counter bodies. In addition to that, benchmark testing is performed with conventional solid lubricant coatings (graphite, MoS2, WS2). Electrophoretic deposition is used as the main coating technique along with air spraying (for WS2). All coatings substantially improve friction compared to the purely laser-patterned reference. Among all coating materials, carbon nanotubes demonstrate superior lubricity and the longest wear life against 100Cr6 and alumina counter bodies. Detailed characterization of the resulting wear tracks by energy-dispersive X-ray spectroscopy, scanning electron microscopy, and confocal laser scanning microscopy provides insights into the friction mechanisms of the various solid lubricant particles. Further, material transfer is identified as an important aspect for effective and long-lasting lubrication.

Generation of Textured Surfaces by Vibration-Assisted Ball-End Milling

Article

Full-text available

May 2023

Textured surfaces have been widely applied in many fields due to their excellent functional performances. Although several micro-scale surface texturing techniques have been used to fabricate surface textures, most are either very expensive, have material limitations, or lack flexibility. In this study, a novel textured surface generation method using vibration-assisted ball-end milling with a non-resonant vibrator is proposed. Firstly, the configuration of the vibration-assisted ball-end milling system is introduced. Then, the trajectories of the cutting edges are modeled and analyzed. Furthermore, an analysis of a non-resonant vibrator is conducted. Finally, surface texture machining experiments are conducted, and the feasibility of the proposed vibration-assisted ball-end milling method for surface texture fabrication is verified.

The Effect of Star Shaped Dimples on Sliding Surfaces under Hydrodynamic Lubrication

Article

Full-text available

Nov 2023
Tribol Online

Tribological behaviour of sliding surfaces with star shaped micro-dimples on one of the surface is reported. One wall is smooth and sliding on the other fixed dimpled wall with constant velocity. Effect of star shaped dimple and oriented star shaped dimple has been compared with circular shaped dimple for hydrodynamic pressure generation and tribological behaviour. Effect of dimple depth, dimple area density and sliding speed on tribological behaviour were also analyzed. The results demonstrate that an unconventional star-shaped and orientated star-shaped dimple produces a larger net hydrodynamic pressure in the fluid domain and provides better stability between the sliding surfaces than a circular-shaped dimple. It is shown that geometric parameters like dimple depth and dimple area density and operation parameter like sliding speed affects the hydrodynamic average pressure and tribological behaviour of sliding surfaces significantly. The experimental findings validate the analytical and CFD findings.

The Behavior of TiAlN and TiAlCrSiN Films in Abrasive and Adhesive Tribological Contacts

Article

Full-text available

Sep 2023

Chromium and silicon are often introduced to increase the performance of TiAlN hard coatings in dry tribological contacts. The addition of Cr and Si during a high-power impulse magnetron sputtering (HiPIMS) deposition process leads to high-quality TiAlCrSiN films. In this paper, the analysis of friction and wear of these films is conducted by oscillation tribometry under dry conditions with a subsequent mapping of the surface topography. Both abrasion- and adhesion-dominated conditions are realized using different steel counter bodies. Oscillation-frequency-dependent experiments show a significant impact of the compositional variation on friction and wear. It is shown that the TiAlCrSiN coating investigated has a higher coefficient of friction and a lower wear resistance compared to counterparts made of 100Cr6. The friction coefficient could be reduced by using a V2A counterpart. The results can be understood in terms of a reduced adhesion of both oxidic and metallic wear debris at the TiAlCrSiN surface. The study provides valuable progress towards the development of advanced cutting tools, e.g., for stainless steel.

Influence of the Bowtie Shaped Dimples on the Performance of Sliding Surfaces under Hydrodynamic Lubrication

Article

Jul 2023

It covers the tribological behaviour of sliding surfaces, one of which has bowtie-shaped micro-dimples. Against the other fixed, textured wall, one wall is smooth and moving at a constant speed. For the formation of hydrodynamic pressure and tribological behaviour, the effects of bowtie-shaped dimples and orientated bowtie-shaped dimples have been compared with circular-shaped dimples. Additionally, the impact of sliding speed, dimple area density, and dimple depth on tribological behaviour was examined. The findings show that compared to a circular-shaped dimple, an atypical bowtie-shaped and orientated bowtie-shaped dimple generates a higher net hydrodynamic pressure in the fluid domain and offers improved stability between the sliding surfaces. It has been demonstrated that geometrical factors like dimple depth and area density as well as operational factors like sliding speed have a substantial impact on the hydrodynamic average pressure and tribological behaviour of sliding surfaces. The experimental results support the conclusions from the analysis and CFD.

Tribological behavior of polydopamine/polytetrafluoroethylene coating on laser textured stainless steel with Hilbert curves

Article

Full-text available

Nov 2022

Shallow Hilbert curve patterns with easily programmable texture density were selected for laser texturing of stainless steel substrates. Two different texture path segment lengths (12 and 24 µm) and four different laser power percentages (5%, 10%, 15%, and 20%) were investigated. The textured and smooth substrates were coated with thin polydopamine/polytetrafluoroethylene (PDA/PTFE) coatings for tribological property assessment. The effects of texture density (texture area coverage) and laser power on the durability and friction of the coated surfaces were studied. Laser texturing the substrates improved the coating durability up to 25 times, reduced the friction coefficient, and prevented coating global delamination. The textures fabricated with a laser power of 15% and a texture path segment length of 12 µm yielded the best coating durability. The textures provided the interlocking for the PTFE coating and thus prevented its global delamination. Furthermore, the PTFE inside the texture grooves replenished the solid lubricant worn away in the wear track and prolonged the coating wear life.

Potential of Nitrided and PVD-MoS2:Ti-Coated Duplex System for Dry-Running Friction Contacts

Article

Full-text available

Sep 2022

Self-lubricating coatings can be used to increase the service life of machine parts which are subjected to high mechanical loads. The present work is concerned with the combination of nitriding and a subsequent Ti-doped MoS2 coating. The focus of the investigations is on the impact of the compound layer on the wear behavior of the coating since the changes in the surface topography due to compound layer growth and pore formation inside the compound layers are expected to have an impact of the adhesion strength and the wear behavior. For this purpose, compound layers with varying thickness and porosity were formed in the surface area of the material EN31CrMoV9 by gas nitriding. A MoS2:Ti PVD monolayer was applied directly on the compound layers. The wear behavior was evaluated using the pin-on-disc test. The MoS2:Ti solid lubricant coatings show good adhesion on the compound layers without any interlayer. Compared with the nitrided reference state, the coating significantly improved the wear behavior of the surface treated material.

High-Temperature Solid Lubricants and Self-Lubricating Composites: A Critical Review

Article

Full-text available

Aug 2022

Solid lubricants are described as solid materials of intentionally introduced or in situ formed on contact surfaces in relative motion for the purpose of lowering friction and wear and providing protection from damage. Solid lubricants and advanced self-lubricating materials are widely used in modern industries, especially in aerospace, aviation, automotive, metallurgy, materials forming, and machining industries, and have attracted great interest in lubrication applications under very severe circumstances such as elevated temperatures, heavy loads, ultrahigh vacuum, extreme radiation, strong oxidation, and chemical reactivity environments. Many efforts have been made to develop self-lubricating composites by a variety of material preparation techniques, which include powder metallurgy, physical/chemical vapor depositions, thermal spraying, electrodeposition, laser cladding, and additive manufacturing. Although several reviews on the development of high-temperature solid lubricants have been published, most of them only focus on a type of material, a specific process, or application. In this paper, a comprehensive review is provided to present the state-of-the-art progress in solid lubricants, self-lubricating composites/coatings, and their effective functions that can be used over a wide variety of environmental conditions, especially at elevated temperatures. The solid lubricants considered include representative soft metals, layered structure materials (e.g., graphite, hexagonal boron nitride, transition metallic dichalcogenides, MAX phase), chemically stable fluorides, binary or ternary metallic oxides, especially alkaline earth chromates, and sulfates, and synergistic effects from these solid lubricants. This paper also provides new insights into design considerations of environmental adaptive solid lubrication, and the challenges and potential breakthroughs are further highlighted for high-temperature solid lubrication applications.

Combining Surface Textures and MXene Coatings – Towards Enhanced Wear-Resistance and Durability

Article

Jun 2022

Surface texturing has gained significant attention over the last 30 years to tailor friction and wear under various tribological conditions in fundamental and applied tribological systems. Under dry conditions, surface textures help to improve friction or wear by reducing adhesion and the real area of contact as well as trapping wear particles. However, especially under high load conditions, surface textures rapidly wear away, thus losing their friction- and wear-reducing capability. A potential strategy to improve their durability under more severe conditions is the combination with protective solid lubricant coatings. In this regard, MXene nano-sheets are the most recent success story related to 2D materials as solid lubricant coatings. They appear particularly interesting due to their ability to generate low-friction and wear-resistant tribo-films thus providing an excellent durability and wear resistance. This aspect makes the combination of MXene solid lubricant coatings and surface textures highly prospective. Therefore, this perspective aims at summarizing and analyzing the existing state-of-the art related to the combined use of surface textures and MXene coatings.

Combined lubrication of surface texturing and copper covering for broaching tool

Article

Full-text available

Mar 2022
INT J ADV MANUF TECH

Broaching is widely used in the aerospace field owing to its high efficiency and heavy load. However, heavy-load cutting causes intense squeezing and friction in the tool-chip contact area, resulting in a lack of lubrication. Therefore, three textures (i.e., micro-pit, stripe, mesh) are prepared on the rake face of broaching tool with a laser processing technique to improve cutting performance. Afterward, textures are covered with copper using the reciprocating rotational friction to enhance the wettability and heat dissipation capacity of the broaching tool. Experiments approve that striped textures covered with copper reduce the cutting force by 14.6% and the cutting temperature decreases from 90.13 to 76.9 ℃, compared with non-textured cutting teeth. Obtained results indicate that the wettability of cutting fluid on the tool surface is significantly improved due to the capillary force of micro-pores generated by the copper covering, especially in the direction to the cutting edge. Furthermore, the copper debris absorbs heat quickly in the cutting areas and is subsequently taken away by chips and cutting fluids, thereby reducing the cutting temperature.

Nd:YVO4 Laser Irradiation on Cr3C2-25(Ni20Cr) Coating Realized with High Velocity Oxy-Fuel Technology—Analysis of Surface Modification

Article

Full-text available

Nov 2021

The high-velocity oxy-fuel (HVOF) technique has been extensively used for the deposition of hard metal coatings. The main advantage of HVOF, compared to other thermal spray techniques, is its ability to accelerate the melted powder particles of the feedstock material to a relatively high velocity, leading to good adhesion and low porosity. To further improve the surface properties, a mechanical machining process is often needed; however, a key problem is that the high hardness of the coating makes the polishing process expensive (in terms of time and tool wear). Another approach to achieving surface modification is through interaction with a thermal source, such as a laser beam. In this research, the effects of laser scanning rate, scanning strategy, and number of loop cycles were investigated on an HVOF-coated surface. Cr3C2-25(Ni20Cr) was selected as the coating and Nd:YVO4 as the laser source. The results demonstrate the significance of the starting coating morphology and how the laser process parameters can be tuned to generate different types of modifications, ranging from polishing to texturing.

On the anisotropy in the dry-sliding behaviour of a self-lubricating PTFE composite and the effects from surface texturing

Article

Full-text available

Nov 2021

In self-lubricating sliding contact facilitated with polytetrafluoroethylene (PTFE) composites, the anisotropy in tribological performance was often attributed to the oriented structures of the polymer. However, in this research, it is found that the non-homogeneity introduced by the hard fibres or stiffeners may be the main contributor to the anisotropic tribological performance of the polymeric composites. The interaction between the non-uniformly arranged hard fibres/stiffeners and the metallic counterface was found to be the leading phenomenon of this tribological behaviour. Moreover, the effects from a surface texturing scheme was found capable of establishing intervention to this interaction and reducing the anisotropy. The mechanism of the texturing effects was found related with back-transfer of PTFE and trapping of wear debris.

Laser Processing of Hard and Ultra-Hard Materials for Micro-Machining and Surface Engineering Applications

Article

Full-text available

Jul 2021

Polycrystalline diamonds, polycrystalline cubic boron nitrides and tungsten carbides are considered difficult to process due to their superior mechanical (hardness, toughness) and wear properties. This paper aims to review the recent progress in the use of lasers to texture hard and ultra-hard materials to a high and reproducible quality. The effect of wavelength, beam type, pulse duration, fluence, and scanning speed is extensively reviewed, and the resulting laser mechanisms, induced damage, surface integrity, and existing challenges discussed. The cutting performance of different textures in real applications is examined, and the key influence of texture size, texture geometry, area ratio, area density, orientation, and solid lubricants is highlighted. Pulsed laser ablation (PLA) is an established method for surface texturing. Defects include melt debris, unwanted allotropic phase transitions, recast layer, porosity, and cracking, leading to non-uniform mechanical properties and surface roughness in fabricated textures. An evaluation of the main laser parameters indicates that shorter pulse durations (ns—fs), fluences greater than the ablation threshold, and optimised multi-pass scanning speeds can deliver sufficient energy to create textures to the required depth and profile with minimal defects. Surface texturing improves the tribological performance of cutting tools in dry conditions, reducing coefficient of friction (COF), cutting forces, wear, machining temperature, and adhesion. It is evident that cutting conditions (feed speed, workpiece material) have a primary role in the performance of textured tools. The identified gaps in laser surface texturing and texture performance are detailed to provide future trends and research directions in the field.

Combined Lubrication of Surface Texturing and Copper Covering for Broaching Tool

Preprint

Full-text available

Jun 2021

The broaching tool is an efficient and precisely heavy-loaded metal-cutting tool, widely used in the mass production of key components related to the aerospace and automobile industries. However, the heavy load, intense squeezing, and friction in the tool-chip contact area prevent the cutting fluid from entering the desired location. Consequently, insufficient lubrication gives rise to a high-temperature built-up edge, thereby lowering machining accuracy and efficiency. To reduce frictional force, three textures (i.e., micro-pit, stripe, mesh) are prepared on the rake face of broaching tool with laser processing technique. Afterward, textured grooves are covered with copper using the reciprocating rotational friction; this artifact enhances the system’s wettability and heat dissipation ability. Experiments approve that compared to the non-textured cutting teeth, the cutting force with the stripe-textured teeth is reduced by 7.6%. Nevertheless, the cutting force is decreased by 14.6% after covering the tool surface with copper. Obtained results indicate that the wettability of cutting fluid on the surface is improved. In addition, convex peaks on the tool surface are passivated during the reciprocating rotation of the copper bar.

Study of Parameters of Nano-Second Laser on Polycrystalline diamond to Fabricate Micro-Grooves

Conference Paper

Jan 2021

On the surface of the polycrystalline diamond (PCD) tool, micro-grooves with diverse parameters and characteristics are fabricated using a nano-second laser. The influence of the process parameters of laser on the depth, width, and material removal rate (MRR) of the micro-textures was investigated. The findings have shown a decrease in micro-groove width and depth with the increase of scanning speed, frequency rate, and lower output power. Additionally, the sidewall topography of the micro-grooves depicted the quality could be enhanced or improved by a lower scanning speed or an immense output power. On the basis of experimental outcomes, the process parameters optimization can efficiently and reasonably control the micro-texture dimensions as well as improvement in the surface quality of the PCD tools.

Analysis of dimple structure fabricated using turning process and subsequent reduction in friction

Article

Apr 2019
WEAR

Dimples is an important structure in the context of surface texturing due to its role in improving the heat transfer while minimizing wear and friction on sliding mechanical components. In this study, various sizes and shapes of dimple structures were fabricated on a cylindrical surface of a hyper eutectic aluminum silicon alloy (A390) using the turning process with the aid of a dynamic-assisted tooling (DATT), which was designed and fabricated in-house. The turning process was selected based on factors such as the capability of its machining process, low cost, minimum setup time, and green working environment. The dimples’ shapes fabricated in this study were short drop, long drop, and spherical, with widths of 397–920 µm, lengths of 2420–3261 µm, depths of 64–155 µm, and area ratios of 10–15.68%. The tribology test conducted on the samples confirmed that the coefficient of friction of these dimples in a hydrodynamic regime was 0.22–0.24 relative to the smooth surface's at 0.5, which is a maximum of 56% friction reduction. No microstructural changes were observed beneath the machined surface of the dimpled area and surface roughness (Ra) in the case of both dimple and non-dimpled surfaces. Dimple fabrication using the turning process is therefore recommended to the manufacturing industry if they intend to preserve material properties within friendly working environment(s).

Enhancing tribological properties of WS2/NbC/Co-based self-lubricating coating via laser texturing and laser cladding two-step process

Article

Full-text available

Sep 2020

In order to avoid decomposition of solid lubricants during laser processing and improve the lubrication stability of laser-clad self-lubricating coating, a novel multilayer structural WS2/NbC/Stellite 6 metal matrix self-lubricating coating (MMSC) with laser texturing layer (LTL), lubricant layer (LL) and laser-clad sealing layer (LSL) was fabricated on Cr12MoV steel via laser surface texturing (LST) and laser surface cladding (LSC) two-step process. The microstructure, phase and tribological properties of the multilayer structural MMCC were investigated by means of optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy, as well as dry sliding wear test in wide-temperature (room temperature, 200 °C, 400 °C, and 800 °C). Results show that the multilayer structure partially inhibited the decomposition of the lubricant so that WS2 particles retained in the coating and NbC promoted the formation of a new lubricating phase CrS in decomposed WS2. The multilayer structural coating prepared in two steps had lower friction coefficient (0.226) and wears volume (31.916 mm³) at room temperature (RT). Moreover, the friction coefficient of the multilayer WS2/NbC/Co-based self-lubricating coating was still low (0.306) at 800 °C, only. Adhesive wear was identified as the main wear mechanism and the discrepancies of tribological properties were found to be mainly dependent of the kind of lubricating films generated at the wear surface.

The Influence of Hybrid Surface Modification on the Selected Properties of CP Titanium Grade II Manufactured by Selective Laser Melting

Article

Full-text available

Jun 2020

The human body is an extremely aggressive environment in terms of corrosion. Titanium and its alloys are one of the most popular biomaterials used for implant applications due to biocompatibility. However, every element introduced into the body is treated as a foreign body. The human body’s immune response may, therefore, lead to implant rejection and the need for reoperation. For this purpose, it seems important to carry out surface modifications by applying coatings and inter alia by texturing to implants. The objective of this paper is to investigate the effect of surface treatment on the chosen properties of the pure titanium (Grade II) samples obtained by selective laser melting (SLM) processing. The samples were divided into five groups: Initial state (after polishing), after surface modification by the physical vapour deposition (PVD) method—CrN and TiN coatings were deposited on the surface of the tested material, and after laser texturing. The paper presents the results of the microscopic investigation, chemical and phase compositions, and physicochemical and electrochemical properties of the tested samples. Based on the results obtained it can be concluded that the hybrid surface modification shows significant effects on the properties of the pure titanium. The samples with the textured PVD-deposited TiN coatings were characterized by favorable physicochemical properties and were the highest performing in terms of pitting corrosion resistance.

The effects of initial and in-situ generated roughness on polymer wear: Voluntary vs. involuntary

Article

Feb 2024
WEAR

Application of MoS2 in the space environment: a review

Article

Full-text available

Nov 2023

A considerable portion of space mechanism failures are related to space tribological problems. Cold welding in high vacuum; surface erosion and collision damage caused by various radiations, high temperature oxidation under atomic oxygen (AO) bombardment; and thermal stress caused by temperature alternation all alter the physical, chemical, and friction properties of materials. In particular, the space vibration caused by alternating temperatures and microgravity environments can alter the motion of the contact body, further affecting its friction properties. Improving the friction properties of contact surfaces in the space environment is an important way to extend the service life of spacecraft. Traditional lubricants can no longer meet the lubrication requirements of the space environment. This study describes the characteristics of the space environment and the applications of solid lubricants. The friction properties of MoS 2 , a solid lubricant widely used in space, are discussed. The synergistic lubrication of MoS 2 with surface textures or metals is presented. Advances in research on the friction properties of collision sliding contacts in the space environment are reviewed. The combination of MoS 2 and soft metals with surface textures is introduced to reduce the effects of vibration environments on the friction properties of moving parts in space mechanisms. Finally, the challenges and future research interests of MoS 2 films in space tribology are presented.

Computer Modelling and Comparative Analysis of Surface Microrelief Inspection by the Method of Scattering of a Laser Beam During Its Small-Angle Sliding Incidence

Chapter

Aug 2023

The study of metal surface modification by short nano-fiber laser pulses for the creation of hydrophilic and hydrophobic laser-induced structures (LIPSS) is currently receiving considerable attention. When connecting layers of multilayer ceramic-metal structures made of composite materials, the LIPSS structure can play a significant role in increasing strength. There is a need to create an accessible surface control method for operational control over the change in hydrophobic properties over time. This is because hydrophilic surfaces are formed on steels, as a rule, immediately after irradiation, and hydrophobic ones only after a long time, which can last 3… 7 weeks. To control the surface microrelief, in this paper we study the use of the method of sliding reflection of a helium-neon laser beam. The possibility of effective use of this method for the qualitative determination of the structure of the LIPSS surface from the diffraction pattern of the reflection of a helium-neon laser beam is confirmed.KeywordsSurfaceLIPSSMicrostructureLaser ProcessingSliding Reflection

Recent Progress on Surface Texturing and Solid Lubricants in Tribology: Designs, Properties, and Mechanisms

Article

Mar 2023

This study provides a review of recent progress on designs, properties, and mechanisms of surface texturing and solid lubricants. Firstly, the design and processing of surface texture, the type of solid lubricants and the preparation method of texture combined with lubricants are mentioned in design strategy, respectively. Then, effects of surface texture and solid lubricants on tribological properties are analyzed, including antifriction, wear-resistance and other beneficial effects. Next, the synergistic effect mechanisms of surface texture and solid lubricants are discussed, focusing on the effect of texture on the surface/interface of lubricating coating and the lubrication effect of solid lubricants by texturing. Finally, this review looks forward to the problems and future development of texture and lubricants.

Frictional noise mitigation using synergetic approach of laser surface texturing and bio-lubrication

Article

Nov 2022
TRIBOL INT

In this research study, the effect of laser surface texturing on friction induced noise under dry and lubricated sliding is investigated. Disc samples of EN 31 steel were ablated with dimples of 70 µm with varying pitch. The tribo-tests were conducted in anechoic chamber at a constant normal load of 10 N and frictional noise was studied in relation to sliding frequency and dimple pitch. Textured surfaces with 150 µm dimple pitch reduced friction and noise in lubricated conditions. FESEM and EDS were used to analyze the worn surfaces. Taguchi integrated Grey analysis revealed that optimal average frictional noise and COF are obtained under lubricated conditions with 10 Hz sliding frequency and 150 µm dimple pitch.

Tribological properties of dopamine-modified dimple textured surfaces filled with PTFE

Article

Nov 2022

PTFE-filled textured surfaces were impregnated with the dopamine dipping solution to improve their tribological performances. Ball-on-disc wear experiments were conducted to compare tribological properties of three surfaces: the textured surface, filled textured surface and modified filled textured surface. The worn surfaces, wear debris, and shedding areas of the PTFE were measured, and shear strength between the PTFE block and medium carbon steel after impregnation modification was analysed. Experimental results showed that compared with textured surfaces, filled textured surfaces and modified filled textured surfaces had lower friction coefficient values and cross-sectional areas of wear scars. Compared with the filled textured surface, the modified filled textured surface reduces filled gaps by 63.5% and the shedding ratio of the PTFE within dimples by 63.2%. The research results demonstrate that tribological performances of the filled textured surface can improve after impregnation modification. Polydopamine can react to covalent-noncovalent interaction with PTFE and medium carbon steel. Polydopamine acts as a binder to improve the bonding strength between the PTFE and the inner wall of dimples. Polydopamine can reduce the shedding ratio of the PTFE and maintain the antifriction function of the PTFE in dimples.

Laser surface texturing of both thin polytetrafluoroethylene coatings and stainless steel substrates for improving tribological properties

Article

Jan 2023
POLYM TEST

Hilbert curve patterns were laser-textured on both stainless steel substrates and polytetrafluoroethylene (PTFE) thin coatings by applying 15% and 5% of the 2.3-W full laser power, respectively. The nanomechanical and tribological behavior of both smooth and laser-textured PTFE coatings on both smooth and laser-textured stainless steel substrates were studied. It was found that laser-texturing thin PTFE coatings reduced the hardness of PTFE coatings and prevented the coating from tearing under nanoindenter scratches. Furthermore, laser-texturing on both PTFE coatings and the stainless steel substrate improved the coating wear life 29 times compared to the wear life of the control sample without any laser textures.

Femtosecond Laser Texturing of DLC based coatings by DLW Method with Sub-micrometer Precision

Preprint

Full-text available

Mar 2022

The enhancement of functional surfaces by laser texturing has been investigated in many studies; however, it has been often applied to the substrate. New laser technologies, such as the direct laser writing (DLW) method using a femtosecond laser, allow the production of extremely precise textures into both substrates and thin films. This paper investigates two distinct methods producing various textures: (i) the substrate is textured before the deposition of the diamond-like carbon coating (DLC), and (ii) the texture is produced into DLC coating deposited on a polished substrate. Our goal was to achieve identical topography in both cases; the textured area was as large as 170 mm ² . The textured topography was assessed by 3D laser scanning microscope, which confirmed the repeatability of fs laser processing. Raman spectroscopy mapping, SEM, and XPS were combined to investigate the effect of laser processing on DLC coating in terms of oxidation or structural changes.

Application of Bionic Tribology in Water-Lubricated Bearing: A Review

Article

Mar 2022

Water-lubricated bearing has become the development trend in the future because of its economy and environmental friendliness. The poor friction performance under low speed and heavy load seriously limits the popularization and application of water-lubricated bearings. Learning from nature, the phenomenon of low friction and wear in nature has aroused great interest of scientists, and a lot of research has been carried out from mechanism analysis to bionic application. In this review, our purpose is to provide guiding methods and analysis basis for the bionic design and theoretical research of anti-friction and anti-wear of water-lubricated bearings. The development of water-lubricated bearing materials are described. Some typical examples of natural friction reduction and drag reduction are introduced in detail, and several representative preparation methods are listed. Finally, the application status of bionic tribology in water-lubricated bearings is summarized, and the future development direction of water-lubricated bearings is prospected.

Insertion force reduction of micro-texture on 316 L electrode for Parkinson’s surgery by Laser processing

Article

Mar 2022

Deep brain stimulation is an effective operation in the treatment of Parkinson's disease. In the process of treatment, the electrode needs to be inserted into the brain tissue for positioning, which will cause a certain damage and positioning deviation. The insertion force is the main factor affecting the degree of tissue damage and the accuracy of the target location. Therefore, an effective method to reduce the insertion force can reduce part of the insertion damage. In this research, the micro-texture with different spacing was made on the surface of the needle to form a super-hydrophilic surface and reduce the insertion force. The micro-textured needles after low-temperature annealing with the super-hydrophobic surface are also fabricated. The experiments of different micro-textured needle insertions with different insertion speeds in the porcine brain that were immersed into Artificial cerebrospinal fluid (aCSF) were tested. Besides, the experiments were also tested in vivo rat brains. The results showed that the insertion force of the needle both the textured needle and smooth needle increases with the increase of the speed. The super-hydrophilic textured needle with a certain spacing of 0.1 mm and 0.3 mm can effectively reduce the insertion force. The insertion force is reduced by up to 24% in the porcine brain immersed into aCSF and 14% reduction in vivo rat brain respectively.

Effects of van der Waals interaction on the adsorption of H2 on MoS2 monolayers and nanoribbons

Article

Jan 2022
CHEM PHYS

Density-functional theory calculations are performed to investigate the adsorption of molecular hydrogen onto MoS2 monolayers, armchair nanoribbons, and stacked monolayer-armchair nanoribbon complexes. The van der Waals interaction is explicitly included through the use of three distinct exchange-correlation functionals and a comparison with the use of LDA is made. The adsorption energy, structural properties, band structure are discussed, considering different adsorption sites, nanoribbon dimensions, and H2 concentrations. Recovery time is evaluated for a particular situation where significant adsorption energy is obtained for the monolayer plus nanoribbon complex, -together with a reasonable modification of the electronic structure, in comparison with MoS2 monolayer and free-standing nanoribbons-, pointing at a promising use of this system as a molecular hydrogen sensor.

Effects of Texture Density on the Tribological Properties of PEO/PTFE Coatings Formed on Aluminum Alloys

Article

Nov 2021

Plasma electrolytic oxidation (PEO) coatings are commonly used as protective materials in the automotive industry. In this study, textured PEO coatings with different densities of dimples were fabricated by laser surface texturing, which was followed by coating with self-lubricating polytetrafluoroethylene (PTFE) material by vacuum penetration. The topographies, microstructures and tribological properties of the textured PEO/PTFE coatings were investigated. The results showed that the texture densities had a significant effect on the tribological properties of composite PEO/PTFE coatings. The composite coating with a texture density of 39.7% showed a stable and low friction coefficient of approximately 0.11 under test loads ranging from 5 N to 20 N. In addition, this coating exhibited better carrying capacity than other textured coatings during the friction process. With the increase in dimple area density, the storage capacity of the composite coating increased, and was accompanied by a decreased load-bearing capacity. This led to further contact with the friction interface, which was beneficial to lubrication. An ideal balance between the physical support of the PEO coating and the lubricating effect of the PTFE film was achieved. This article is protected by copyright. All rights reserved

Layered 2D Nanomaterials to Tailor Friction and Wear in Machine Elements - A Review

Article

Full-text available

Dec 2021

Recent advances in 2D nanomaterials, such as graphene, transition metal dichalcogenides, boron nitride, MXenes, allow not only to discover several new nanoscale phenomena but also to address the scientific and industrial challenges associated with the design of systems with desired physical properties. One of the great challenges for mechanical systems is associated with addressing friction and wear problems in machine elements. In this review, the beneficial properties of layered 2D materials that enable the control of their tribological behavior and make them excellent candidates for efficient friction and wear reduction in dry-running and boundary lubricated machine components are summarized. The recent studies highlighting the successful implementation of 2D structures when used as solid lubricant coatings or reinforcement phases in composites for various machine components including sliding and rolling bearings, gears, and seals are overviewed. The examples presented in the studies demonstrate the great potential for 2D materials to address the energy-saving needs by friction and wear reduction.

Surface Texturing

Chapter

Dec 2017

Bojan Podgornik

Volume 18 addresses friction and wear from a systems perspective, while providing a detailed understanding of why it occurs and how to control it. It explains the basic theory of friction and wear, and offers valuable insight on the forces, mechanisms, and interactions that are involved. It examines common wear scenarios, including wear by particles or fluids, rolling-contact wear, sliding wear, impact wear, and both chemical and environmentally assisted wear. It also covers operational wear, addressing several cases, including tool and die wear, bearing wear, engine wear, turbine wear, pump wear, and seal wear. In addition, the volume provides information on lubricants and lubrication, coatings, surface treatments and modifications, and the tribology of irons and steels, cobalt-base alloys, titanium, aluminum alloys and composites, cemented carbides, ceramics, polymers, and polymer composites. It also introduces the topic of condition monitoring, addressing wear particle analysis, vibroacoustic monitoring, and motor current signature analysis. For information on the print version of Volume 18, ISBN 978-1-62708-141-2, follow this link.

Surface Texturing Techniques to Enhance Tribological Performance: A Review

Article

Sep 2021

Texturing of the surface is a technique to form the surfaces of the desired pattern. It is extensively used to alter the mechanical and tribological properties, such as increased fatigue strength, corrosion, wear resistance, anti-biofouling hydrophobicity and load-carrying capacity. To get these benefits, many researchers have studied the importance of textured parameters on metals and non-metals and revealed that un-optimized parameters might deteriorate the properties of the materials. These texture parameters may be dimple shape, depth, diameter, and density. Even though laser surface texturing widely used method, this review article articulates detailed information about surface texturing methods available to fabricate, surface texture characterization, merits, demerits, and applications of textured surfaces on metals and non-metals to enhance tribological performance.

Tribodynamic studies of textured gearsets lubricated with fresh and MoS2 blended greases

Article

Full-text available

Jan 2022
TRIBOL INT

The synergistic effects of surface texture and Molybdenum disulphide (MoS2) blended grease have been explored on the tribodynamic performance of spur gearsets. A texture involving ellipsoidal dimples on the face and flank of pinions' teeth was fabricated using nanosecond pulsed fiber laser. The experiments were performed at different applied torques and a pitch line velocity of 4 m/s keeping in mind the practical application of the results. Contact resistance, vibrations, temperature rise and surface topographies have been measured and analyzed. Substantial increase (about 300%) in contact resistance and reduction (40% approximately) in vibration amplitudes at gear mesh frequency were found in the presence of texture. Reduction in interfacial temperature rise and less damage to teeth surface were also observed.

Improvement in Wear and Friction Properties of Heat-Treated Steel Using Micro-grooved Patterns

Chapter

Jul 2021

Surface wear is one of the leading causes of failures in sheet metal forming dies. Surface wear significantly affects productivity as well as the overall product cost. For forming dies, D2 steel is mostly used. D2 steel is High Carbon High Chromium Steel (HCHCr). In the present work, modern surface modification techniques are investigated to understand their effect on tribological properties such as wear and friction in order to minimize the surface wear failures. Hence Modern surface modification techniques selected are plasma ion nitriding, micro-grooving, and solid lubrication. Plasma ion nitriding is a heat treatment process and carried out in plasma chamber. Micro-grooving was carried out using laser surface texturing. Dimple, rhombus, concentric circular, asterisk, and cross grooves patterns were used for micro-grooving. 5 Samples of D2 steel were prepared using heat treatment (plasma ion nitriding) and micro-grooving (laser surface texturing). Wear and friction coefficient of samples of untreated and treated D2 steel were determined on pin-on-disc Tribometer. Tests were conducted at room temperature with alumina pin (99.99% pure) and D2 steel plate samples with Graphite as a Solid lubricant. The micro-grooves provide storage spaces for graphite, indirectly improves the life of lubricant. Hence micro-grooving and solid lubrication help for effective improvement in the tribological properties. The outcome of this research work is very promising and showed reduction in wear and friction coefficient up to 95% and 80%, respectively, when these modern surface modification techniques are used.

Conformable Metal Oxide Platelets - A Smart Surface Armor for Green Tribology

Article

Jun 2021
TRIBOL INT

The reduction of friction and wear is a crucial performance criterion for most technical processes. This is particularly true for the ubiquitous case of oil lubricated machinery made from steel components. Here we introduce a facile laser treatment that significantly enhances the tribological performance of bearing steel 100Cr6, a material widely used for the manufacture of ball and roller bearings. By applying repeated nanosecond-pulses of focussed laser-beam irradiation under ambient air, a surface-protective tribo-layer is generated by a method that exploits self-organization for the formation of conformable metal oxide platelets consisiting of vertically aligned transition metal oxides nanorods on the steel substrate. These submicron-sized metal oxide platelets protect the surfaces similar to scale armor and the tribological performance of the bearing steel 100Cr6 was significantly enhanced. Based on laboratory tests using a rotational pin-on-disk tribometer under oil lubricated conditions, close to zero wear with simultaneous reduction of friction by 54% was achieved. Even under the harsh conditions in the pin-on-disk tribometer these metal oxide platelets turn out to be remarkably robust against detachment and crumbling for lasting millions of cycles at a slip rate of 100%. The origin of this resilience is based on a special substructure of the platelets that, counter-intuitively for ceramic material, enables shape adaptations to surface deformations emergent upon high mechanical stress.

Dynamics analysis and wear prediction of rigid-flexible coupling deployable solar array system with clearance joints considering solid lubrication

Article

Jan 2022

This study considers a solar array system as an example to explore the dynamic responses and wear characteristics of a multi-body system considering clearance joints with solid coating. A rigid-flexible coupling system is established based on the NCF–ANCF formulation, and the clearance joint model is established based on a novel contact law considering coating, a modified Coulomb’s friction law, and Archard’s wear law. The results of the deployment process dynamics of the solar array system with different coatings reveal the effects of coating, material, and coefficient of restitution on the impact properties of the rigid system and rigid-flexible coupling system. Meanwhile, the results of the attitude adjustment dynamics of the system with different coatings and clearance sizes reveal the effects of coating and material on the wear prediction of the rigid system and rigid-flexible coupling system. The effects of coating on the spacecraft attitude are also discussed. This exploration of the effects of solid lubrication of clearance joints on the dynamics of space deployable solar array systems is likely to guide practical engineering design for clarity and readability.

Self-Lubrication Mechanism of Plasma-Sprayed Cr2O3-Ag Nanocomposite Coatings at Room to Moderate Temperatures

Article

Jun 2021
J THERM SPRAY TECHN

Lubrication mechanisms of plasma-sprayed Cr2O3-Ag nanocomposite coatings were studied by using ball-on-disk friction tests against tungsten carbide counterface at temperatures ranging from 25 to 500 °C. The Cr2O3-Ag nanocomposite coatings were fabricated from agglomerated granules of chromium oxide and silver nanoparticles by plasma spraying process under optimized parameters. The presence of semi-molten nanoparticle zones within the coating promoted a sliding wear behavior characterized by plastic deformation of nanostructured ceramic matrix coatings. The formation of a silver-rich tribofilm on top of the contact surface and tribodecomposition of Cr2O3, as well as tribo-oxidation of Ag at the sliding interface were found to be the controlling mechanisms of friction in these coatings at moderate to high temperatures. The lowest coefficient of friction (COF) at all temperatures was obtained for the Cr2O3-5 vol. % Ag coating due to the optimum condition of its silver-rich tribofilm.

Effect of dimple shape and depth on tribological performance of textured surface

Conference Paper

Jan 2021

The study on the relationship between the friction characteristic and the formability of the automotive steel sheet during the stamping process

Article

Full-text available

Nov 2020

This study aims to analyse the formability characteristics by friction characteristics of automotive steel sheets to improve sheet forming during the stamping process. During the stamping operation, the steel sheet is pushed into the tool surface, a complex phenomenon occurs, and many parameters interact. Therefore, automotive steel researchers want to optimize the friction of automotive steel sheets to improve the forming process, such as drawing ratio limit, dome height limit, cup drawing test, etc. In addition, in this study, the finite element method is used in combination with a numerical solution to present the friction behavior of high strength steel sheets in automobiles, taking into account the operating deformation mechanism during the formability test.

Research on the bionic design of the middle trough of a scraper conveyor based on the finite element method

Article

May 2019

Working life of the middle trough is an important indicator of the scraper conveyor. Improving the wear resistance of the middle trough can effectively prolong the service life. Based on the nonsmooth wear-resistant theory, the bionic optimization of the middle trough was carried out by designing the pits on the surface of the middle plate. The orthogonal test design of L 9 (3 ⁴ ) four factors and three levels was used. The structural static analysis and frictional contact analysis of the original middle trough sample and nine groups of the bionic middle trough samples were carried out respectively, and the simulation results were compared. Results showed that the pits had stress slow-release effect, torque effect, edge strengthening effect, and the function of collecting wear debris. So the pits could reduce fatigue wear, abrasive wear, impact wear, adhesive wear, thermal fatigue, and thermal wear on the middle trough. Then, the influence of pits' parameters on the wear resistance of the nonsmooth surface was studied by the contact analysis of the rectangular blocks. Results showed that the surface of the pit was easily deformed to produce more compressive and bending strain energy. The pits had the effect of releasing stress thus improving the wear resistance of the nonsmooth surface. At the same time, with the increase of the length and spacing of the pits, the wear resistance of the nonsmooth surface increased first and then decreased. There was an optimal value as the length of the pit was 2 mm and spacing was 9 mm. With the increase of the pit depth, the wear resistance of the nonsmooth surface increased gradually.

Tribological Study on Sliding Contact Between Laser Surface Textured Titanium and Aluminium Alloy Under Lubrication

Chapter

Jan 2021

Nanocomposite tribological coatings with “chameleon” surface adaptation

Article

Full-text available

Jul 2002

Nanocomposite tribological coatings were designed to respond to changing environmental conditions by self-adjustment of their surface properties to maintain good tribological performance in any environment. These smart coatings have been dubbed “chameleon” because, analogous to a chameleon changing its skin color to avoid predators, the coating changes its “skin” chemistry and structure to avoid wear. The concept was originally developed using WC, diamondlike carbon, and WS 2 material combination for adaptation to a humid/dry environment cycling. In order to address temperature variation, nanocompositecoatings made of yttria-stabilized zirconia (YSZ) in a gold matrix were developed with encapsulated nanosized reservoirs of MoS 2 and diamondlike carbon (DLC). Coatings were produced using a combination of laser ablation and magnetron sputtering. They were characterized by x-ray photoelectron spectroscopy,x-ray diffraction, transmission electron microscopy, x-ray energy dispersive spectroscopy, and micro-Raman spectroscopy. Results were correlated with mechanical and tribological characterization. Coatinghardness was evaluated using nanoindentation, while coating adhesion and toughness were estimated using scratch and Vickers indentation tests. Friction and wear endurance measurements of YSZ/Au/MoS 2 / DLC coatings against steel and Si 3 N 4 balls were performed at room temperature in controlled humidity air, dry nitrogen, and vacuum environments, as well as at 500 °C in air. Depending on the environment, coatingfriction surface changed its chemistry and structure between (i) graphitic carbon for sliding in humid air [coatingfriction coefficients (c.o.f. 0.10–0.15)], (ii) hexagonal MoS 2 for sliding in dry N 2 and vacuum (c.o.f. 0.02–0.05), and (iii) metallic Au for sliding in air at 500 °C (c.o.f. 0.10–0.20). The unique coating skin adaptation realized with YSZ/Au/MoS 2 / DLC and WC/DLC/WS composites proves a universal applicability of the chameleon design concept.

Laser surface microstructuring to improve tribological systems

Article

Full-text available

Sep 2003
Proceedings of SPIE

The controlled laser patterning of solid surfaces improves their wear properties: laser generated microcraters of defined dimensions and morphology can act as lubricant reservoirs and as traps for wear particles. For generating such microstructures different techniques are possible; however laser ablation has the advantage of a great versatility, since it can be adapted to produce a wide range of structures crater arrangements. We have generated microstructures with ps- and ns- pulses on TiN coated steel, uncoated steel and on uncoated steel with was subsequently coated with TiCN. Laser patterning of metals with pulses in the 100ns range is very effective however the process is governed by local melting and vaporization. The melt ejection yields the formation of resolidified droplets and rims on the target surface. This undesired artifacts can be removed by gentle polishing. Furthermore, a recast layer of increased hardness and brittleness of about 1µm thickness which homogeneously covers the crater walls is observed. Tribological tests were performed using the ball-on-disk method. The lifetime of the structured samples, defined as the sliding distance after which the friction coefficient showed an abrupt increase, was found to be significantly enhanced for all structured surfaces. The enhancement ranged from a 30% lifetime increase when TiN coatings were directly structured to an increase of over 10 times for structured hard metal which was subsequently coated with TiCN. To evaluate the possibility of circumventing some of the drawbacks of laser ablation in the ns regime, mainly the melt rims on the surface and the recast layer film on the crater walls of the single microholes the quality of microstructures produced in various metals with pulses of femtosecond duration was studied. To that end the evolution of the ablated depth over a large number of incident femtosecond laser pulses and the occurrence of structure and hardness changes in the immediate vicinity of the laser induced craters was analyzed for two sorts of steel and for hard metal. The analysis evidenced changes in the crystalline structure of the target materials in the fluence regime above 2J/cm2 but only minor alterations up to this fluence. Hardness measurements were performed on the cross-section surfaces in points situated in the immediate vicinity of the laser induced pores. Affected zones in the material surrounding few pores induced in the fs- regime were found and in such zones a significant hardness increasing was evidenced.

Combined magnetron sputtering and pulsed laser deposition of carbides and diamond‐like carbon films

Article

Full-text available

Jul 1996
APPL PHYS LETT

A hybrid technique is reported, which combines magnetron sputtering and pulsed laser ablation to produce plasma fluxes intersected on a substrate surface to form metal, ceramic and diamond‐like materials. Deposition of crystalline Ti, TixCy, TiCN, and amorphous diamond‐like carbon films at low temperatures by the new technique is discussed. The variation of laser pulse frequency is found to be a simple way to control film chemical composition. The technique can be used to prepare materials with transitional structure, as, for example, between metal carbides and diamond‐like carbon.

State of the Art in Laser Surface Texturing

Article

Full-text available

Jan 2005

I. Etsion

Surface texturing has emerged in the last decade as a viable option of surface engineering resulting in significant improvement in load capacity, wear resistance, friction coefficient etc. of tribological mechanical components. Various techniques can be employed for surface texturing but Laser Surface Texturing (LST) is probably the most advanced so far. LST produces a very large number of micro-dimples on the surface and each of these micro-dimples can serve either as a micro-hydrodynamic bearing in cases of full or mixed lubrication, a micro-reservoir for lubricant in cases of starved lubrication conditions, or a micro-trap for wear debris in either lubricated or dry sliding. The present paper reviews the current effort being made world wide on surface texturing in general and on laser surface texturing in particular. It presents the state of the art in LST and the potential of this technology in various lubricated applications like mechanical seals, piston rings and thrust bearings. The paper also describes some fundamental on going research around the world with LST.

Nanostructured Thin Films and Nanodispersion Strengthened Coatings

Book

Jan 2004

This volume contains proceedings of the NATO-Russia Advanced Research Workshop on Nanostructured Thin Films and Nanodispersion Strengthened Coatings (December, 2003, Moscow). During this Workshop leading researchers from twelve countries had presented and discussed most recent developments in the fields of plasma physics and surface engineering related to the preparation and applications of nanostructured thin films and nanodispersion strengthened coatings. These presentations are encompassed in 31 individual chapters. The chapters are assembled in five parts in according to the workshop sessions. Part I is a compilation of chapters on hard and tribological coatings. The recent advances in this area are significant in that it is now possible to engineer strong, hard, and tough coatings that can operate at temperatures higher than 1200 ?C and exhibit ‘smart’, adaptive characteristics. These coatings are based on an amorphous matrix, e. g. nitrides, carbides, borides, or carbon, in which there is a controlled nucleation and growth of ultra hard nanoparticles of crystalline carbides, nitrides, borides and oxides. The critical feature is the control of both the particle size, i. e. , less than 10 nm, and interpartical spacing of a few nanometers. The ‘smart’ or adaptive characteristic is engineered into the nanostructures using similar sized (less than 10 nm) particles of metallic chalcogenidese, ductile metals, or glass forming elements to provide high lubricity and chemical adaptation at the environment change, e. g. , high and low humidities and temperatures.

Laser Applications in Tribology of Hard Materials and Coatings

Article

Jan 2000
NEW DIAM FRONT C TEC

A laser ablation technique is demonstrated to be an effective tool for improving the friction and wear properties of hard materials and coatings, such as polycrystalline diamond films, single crystal sapphire plates, and thin TiN coatings on steel substrates. This paper is particularly concerned with the effects of laser-controlled diamond nucleation, laser polishing of diamond films, and laser microstructuring of hard surfaces. Laser-controlled seeding and early diamond growth is shown to enable the deposition of ultrathin diamond films that exhibit self-lubricating properties in sliding friction against ruby. Thicker diamond films, which are highly abrasive, can be easily converted into low-friction coatings by laser polishing. The relative contribution of the roughness and surface graphitization to the friction behaviour of the laser-polished diamond films is discussed. Laser-etched microstructures on the surface of sapphire flats and TiN-coated steel samples are shown to act as reservoirs for a liquid lubricant, resulting in increased durability of the lubricated sliding of the laser-patterned samples against a steel ball as compared to nonpatterned samples.

Preparation and friction characteristics of self-lubricating TiN-MoS2 composite coatings

Article

May 1996
MAT SCI ENG A-STRUCT

Composite coatings consisting of distinctly discrete phases of TiN and MoSâ were codeposited on graphite and Ti-6Al-4V substrates from Ti((CH3)2N)4/NH3/MoF6/H2S gas mixtures. Chemical composition and microstructure of the coatings were studied by Auger electron spectroscopy, XRD, and TEM. Friction coefficients at room temperature in air were typically in the range of 0.07 to 0.3; they remained comparable at 573 K, but increased to 0.7 to 1.0 at 673 K. A friction coefficient of â¼0.3 was, however, obtained from a composite coating tested at 973 K.

Mechanistic study of the synergism between Sb2O3 and MoS2 lubricant systems using Raman spectroscopy

Article

May 1993
WEAR

A number of materials have been added to MoS2 to improve its lubricating properties. However, the mechanism underlying this improvement is not fully understood. Perhaps the most widely used and studied additive is Sb2O3. While not a lubricant itself, it acts synergistically with MoS2 to improve friction and wear properties. This paper is directed towards developing a better fundamental understanding of the synergism between Sb2O3 and MoS2 in adhesively bonded films. A commercial preparation was used to form the films and laser Raman spectroscopy was used to analyze them before and after rubbing. It is shown that films layer as a result of tribostress — MoS2 preferentially coats film surfaces and Sb2O3 becomes enriched in the next deeper layer. The mechanism proposed to explain the synergistic behavior is that only the thin layer of MoS2 residing on top is exposed to degradation from the environment. The Sb2O3 layer acts as a thermal and oxygen diffusion barrier to retard oxidation deeper into the film. Sb2O3 also acts as a beneficial support for MoS2 as was demonstrated earlier by Centers (Tribol. Trans., (1987) 149). The proposed mechanism suggests that protection is provided against tribo-oxidation but not necessarily thermal oxidation. To validate this concept, wear oxidation is evaluated insitu using a Raman tribotester and the results are compared with thermal oxidation data. Films containing Sb2O3 are indeed more resistant to tribo-oxidation than MoS2 films. It is also shown that the transfer film surface is enriched with MoS2. This indicates that friction is primarily governed by MoS2 rubbing against MoS2 and that Sb2O3 plays a secondary role.

Tribological performance of MoS2 compacts containing MoO3, Sb2O3 OR MoO3 and Sb2O3

Article

Feb 1988
WEAR

Phillip W. Centers

Selected oxides and sulfides have been previously investigated as bulk additives to enhance the tribological performance of MoS2 in air from ambient temperature to about 315 °C. Sb2O3, in particular, has been identified as a superior additive for high temperature aerospace applications. In experiments designed to investigate a hypothesis that the superior tribological performance of MoS2-Sb2O3 formulations results from formation of an Sb2O3-MoO3 eutectic, compacts of MoS2 with MoO3, Sb2O3 or MoO3 and Sb2O3, were prepared and tribologically evaluated at 316 °C. Formulations containing Sb2O3 or MoO3 resulted in higher friction but much less wear than MoS2 compacts, with the wear volume of MoS2-MoO3 compacts at about half that of compacts containing Sb2O3. Data from compacts containing mixtures of MoO3 and Sb2O3 indicate no synergism between the additives, as would be expected if an eutectic of MoO3-Sb3O3 yields any significant benefits in MoS2-Sb2O3 formulations as hypothesized previously. In fact, X-ray diffraction and differential thermal analysis data indicated no evidence of eutectic formation. Alternatively, it is hypothesized that these soft oxides, owing to their low shear strength, permit MoS2 crystallites to retain a preferred orientation achieved during asperity contact, improving the overall tribological performance.The protective role of MoO3 in MoS2 compacts is anomalous in that MoO3, a product of the oxidation to be avoided in high temperature applications of MoS2, is tribologically beneficial in compacts with MoS2 in such applications.

Preparation and characterisation of low-friction TiB 2-based coatings by incorporation of C or MoS 2

Article

Jun 1998
SURF COAT TECH

Hard, low-friction, TiB2-based coatings incorporating C or MoS2 have been synthesised by magnetron co-sputtering from TiB2 and C or MoS2 targets. The coating microstructure was characterised by glancing angle X-ray diffractometry and photoelectron spectroscopy. The friction coefficient was measured using pin-on-disk tribometry and hardness by nanoindentation. Our TiB2–C coatings were found to consist of two phases, diamond-like carbon (DLC) and a hexagonal TiB2 type structure into which carbon is incorporated. A friction-reducing effect was observed only at C concentrations above 66%, where a significant quantity of DLC phase was able to form. For TiB2–MoS2 coatings, a reduced friction was observed, even at low concentrations of MoS2. With both types of lubricants, a trade-off between hardness and friction coefficient was found. Coatings exhibiting a relatively high hardness of 20GPa and friction coefficients as low as 0.05 could be obtained by choosing a suitable composition. Low friction could be obtained for temperatures as high as 400°C for the TiB2–MoS2 coatings, whilst the TiB2–C coatings exhibited a sharp increase in friction coefficient above 150°C.

Microstructure and lubrication mechanism of multilayered MoS 2 /Sb 2 O 3 thin films

Article

Feb 2006

Multilayered MoS2/Sb2O3 thin films were prepared by pulsed laser deposition on steel substrates. A rotary multi-target holder was used to switch the laser targets for alternative growth of MoS2 and Sb2O3 layers providing nanometers thickness. The tribological properties of the films were measured in dry and wet environments and the wear scars were observed using a scanning electron microscope. The multilayer films showed a much longer wear life than pure MoS2 films in wet air tribotests. Focused ion beam and transmission electron microscopies were used to investigate the cross-sectional microstructures of wear scars. Lubricious MoS2/Sb2O3 tribofilms were built up on wear scar surfaces, and produced low friction. Micro-cracks occurred along the interface between the tribofilm and the neighboring/topmost Sb2O3 underlayer, where the Sb2O3 layer effectively inhibited the crack propagation perpendicular to the interface. The orientation of MoS2 crystals in as-deposited films was mostly random and friction-induced stress oriented the MoS2 basal planes parallel to the surface. The reorientation was confined to the topmost MoS2 layer and was not observed below the first intact Sb2O3 layer.

Hole formation process in laser deep drilling with short and ultrashort pulses

Article

Feb 2002

The drilling process in different materials (diamond, steel, ceramics and PMMA) was studied for a large range of pulse lengths from about 100 fs to 10 ns using different approaches. In transparent materials the penetration process was visualized with high-speed video analysis and microscopy. The drilling rate as well as the relation between processing energy density and ablation threshold were determined in situ. The penetration of the laser beam inside the channel and the influence of laser-ignited plasma were investigated by transmission measurements. Mechanisms of energy coupling and heat losses were examined by applying simple analytical calculations. Proposals for the basic understanding of the drilling process are presented.

The effect of substrate surface roughness on the friction and wear of sputtered MoS2 films

Article

Jul 2000

This paper examines how the durability and friction of thin films of molybdenum disulphide are affected by the surface roughness of the substrate to which they are applied. Three types of substrate, representing a variety of bearing materials (bearing steel, titanium alloy and hot-pressed silicon nitride), were prepared with surface roughnesses of nominally 0.04, 0.1, 0.2 and 0.4 µm (centre line average values). Onto these substrates were deposited 1 µm thick films of sputtered MoS2. Pin-on-disc tests undertaken in high vacuum indicated that both film friction and film durability varied appreciably with substrate surface roughness. The most durable films were those applied to silicon nitride substrates. With this film/substrate combination, the onset of film failure was more gradual than that seen with the films applied to metal substrates, and the MoS2 film was observed to recover its low friction properties several times before complete failure. Results from these experiments are presented and a theoretical model, based on the numerical simulation of friction between contacting rough surfaces, is introduced and is used to explain qualitatively the variation in MoS2 film friction with the surface roughness of metallic substrates. Possible reasons for the poor agreement between the model and those results obtained with silicon nitride substrates are discussed.

Interpretation of friction and wear properties of MoS2 coated steel substrates

Article

Sep 1994
WEAR

In a series of experiments, the friction coefficients and durability of steel substrates coated with thin films of molybdenum disulphide have been studied, for various values of the substrate roughness and the film thickness. The results are interpreted using a previously developed numerical contact model which simulates multiple asperity contact between rough surfaces. An additional mechanism involving failure by smoothing is suggested as a possible explanation of trends in previously obtained data for this tribological system.

Femtosecond laser ablation of diamond-like carbon films

Article

Jan 2004
APPL SURF SCI

Diamond-like carbon (DLC) coatings were deposited on Si substrates using a hot filament diode discharge and they were irradiated with ultrashort laser pulses (800 nm, 150 fs, <4 J/cm 2). The laser-treated films were examined using optical microscopy, Raman spectroscopy, SEM, AFM and white-light interferometery. Damage threshold of 0.16 J/cm 2 and ablation rates below 110 nm/pulse were determined. Changes in the structure of the laser-irradiated films were showed by means of Raman investigations. The laser-treated samples were etched and the depths of modified material layers were determined. Ablation experiments with longer laser pulses (1064 nm, 100 ns, <3 J/cm 2) were also performed and the irradiated DLC films were afterwards analyzed using the same procedures. Dissimilarities in the structure changes induced by fs-and ns-laser irradiation were observed and comments are given.

Hybrid Plasma Deposition Methods for Synthesis of Nanostructured Materials

Chapter

Jan 2004
ChemInform

Hybrid deposition techniques facilitate a high degree of structural control at low substrate temperatures, permitting growth of nanostructured materials, which are not possible to produce by other methods. Several hybrid processes were studied, where pulsed plasma plumes from an excimer laser ablation were combined with continuous plasma generated by non-pulsed sources. One was a hybrid of laser ablation and ion beam deposition, where short-lived interactions between two plasma sources were explored to produce AlON films. The process was used as a base for the development Al2O3/MoS2 nanocomposite coatings. Another hybrid process was a combination of laser ablation with magnetron sputtering (MSPLD), where highly energetic plasma plumes from laser ablation were intersected with a magnetron-generated plasma containing sputtered metal atoms. MSPLD was used to prepare a number of nanostructured coatings, including WC/DLC, WC/DLC/WS2, YSZ/Au, and YSZ/Au/MoS2/DLC nano-composites for wear protection of engineering components. Recently we initiated exploration of a new hybrid process, using filtered vacuum arc and magnetron sputtering, as an aletranative to MSPLD. Initial studies were performed in preparing Ti-TiC-DLC and Ti-TiC-CNx functionally gradient coatings.

Smart Nanocomposite Coatings with Chameleon Surface Adaptation in Tribological Applications

Chapter

Jan 2004

Smart nanocomposite tribological coatings were designed to respond to changing environmental conditions by self-adjustment of their surface properties to maintain good tribological performance in any environment. These coatings have been dubbed “chameleon” because of their ability to change their surface chemistry and structure to avoid wear. The first “chameleon” coatings were made of WC, WS2, and DLC; these coatings provided superior mechanical toughness and performance in dry/humid environmental cycling. In order to address temperature variation, the second generation of “chameleon” coatings were made of yttria stabilized zirconia (YSZ) in a gold matrix with encapsulated nano-sized reservoirs of MoS2 and DLC. High temperature lubrication with low melting point glassy ceramic phases was also explored. All coatings were produced using a combination of laser ablation and magnetron sputtering. They were thoroughly characterized by various analytical, mechanical, and tribological methods. Coating toughness was remarkably enhanced by activation of a grain boundary sliding mechanism. Friction and wear endurance measurements were performed in controlled humidity air, dry nitrogen, and vacuum environments, as well as at 500–600 °C in air. Unique friction and wear performance in environmental cycling was demonstrated.

Multi-environmental lubrication performance and lubrication mechanism of MoS2/Sb2O3/C composite films

Article

Aug 2006

MoS2–Sb2O3–C composite films exhibit adaptive behavior, where surface chemistry changes with environment to maintain the good friction and wear characteristics. In previous work on nanocomposite coatings grown by PVD, this type of material was called a “chameleon” coating. Coatings used in this report were applied by burnishing mixed powders of MoS2, Sb2O3 and graphite. The solid lubricant MoS2 and graphite were selected to lubricate over a wide and complementary range including vacuum, dry air and humid air. Sb2O3 was used as a dopant because it acts synergistically with MoS2, improving friction and wear properties. The MoS2–Sb2O3–C composite films showed lower friction and longer wear life than either single component MoS2 or C film in humid air. Very or even super low friction and long wear-life were observed in dry nitrogen and vacuum. The excellent tribological performance was verified and repeated in cycles between humid air and dry nitrogen. The formation of tribo-films at rubbing contacts was studied to identify the lubricating chemistry and microstructure, which varied with environmental conditions. Micro-Raman spectroscopy and Auger electron spectroscopy (AES) were used to determine surface chemistry, while scanning electron microscopy and transmission electron microscopy were used for microstructural analysis. The tribological improvement and lubrication mechanism of MoS2–Sb2O3–C composite films were caused by enrichment of the active lubricant at the contact surface, alignment of the crystal orientation of the lubricant grains, and enrichment of the non lubricant materials below the surface. Sb2O3, which is not lubricious, was covered by the active lubricants (MoS2–dry, C–humid air). Clearly, the dynamics of friction during environmental cycling cleaned some Sb2O3 particles of one lubricant and coated it with the active lubricant for the specific environment. Mechanisms of lubrication and the role of the different materials will be discussed.

Investigation into three-dimensional laser processing of tribological coatings

Article

Aug 1998
SURF COAT TECH

Tribological coating design has evolved from single layer/single phase to multilayer and composite architectures. The early single-layer coatings were not efficient for arresting cracks, distributing loads, relaxing stress, and preventing adhesive failures. Second-generation coatings with multilayer, gradient, and composite architectures added another dimension to the coating design and allowed much better accommodation of stresses and crack arresting. This paper considers the further evolution of coating design to three dimensions, where the lateral property variation was added to the cross-thickness property variation. The three-dimensional design considerably improved the tribological characteristics of hard coatings, by permitting solid lubricant replenishment inside the friction contacts. A functionally gradient Ti–TiC–TiC/diamond-like carbon coating with an upper layer of a tough nanocrystalline/amorphous composite was used for load support, crack prevention, and stress equalization. This coating was processed with laser irradiation to form grooved tracks along wear paths, which were then filled with MoS2. This provided a solid lubricant reservoir in the lateral dimension of the coating. The three-dimensional coating was tested in long-duration sliding tests at fixed and cycling humidity. The coating exhibited environmental adaptation with friction coefficients of 0.15 in humid air and 0.02 in dry nitrogen. The wear life was increased by at least one order of magnitude in comparison to that for a hard gradient coating with a top layer of MoS2 without any three-dimensional laser processing. Discussions of three-dimensional coating tribological properties, friction and wear mechanisms are provided. The environmental adaptation achieved with three-dimensional coating processing can be beneficial for aerospace applications.

Effect of discontinuous hard under-coating on the life of solid film lubricant under extreme contact pressure

Article

Jun 1997
TRIBOL INT

Wear life of bonded molybdenum disulfide film lubricant applied on discrete sections of chromium electroplated to an aluminum alloy substrate under extreme contact pressure was investigated. Block-on-ring tests with ridge-shaped, hardened stainless steel blocks and lubricant coated rings were carried out in a nitrogen atmosphere for several kinds of ring materials including this under-coating. All tests except those for the discontinuous chromium under-coating indicated large or unstable friction soon after the tests started. Discontinuous chromium coating demonstrated a stable friction coefficient of around 0.05 for a long time and the lubricant film remained intact after the test. This is because discontinuous chromium coating on aluminum substrate deformed along the shape of the ridged-block and contact pressure was decreased to several hundred MPa.

Supertough wear-resistant coatings with ‘chameleon’ surface adaptation

Article

Jul 2000
THIN SOLID FILMS

The chameleon's ability to change skin color depending on environment to increase its chances of surviving served as an inspiration in the development of self-adaptive supertough wear-resistant coatings. Surface chemistry, structure and mechanical properties of these thin (0.5 μm) coatings reversibly change with applied load and environment, providing the best wear protection. Coating designs developed in-house are reviewed together with a critical analysis of design reports in the literature. ‘Chameleon’ coatings were prepared using novel nanocomposite structures, consisting of crystalline carbides, diamond-like carbon (DLC), and transition metal dichalcogenides. Various mechanisms were activated to achieve surface self-adaptation and supertough characteristics. They included: transition of mechanical response from hard and rigid to quasi plastic by grain boundary sliding at loads above the elastic limit; friction induced sp3→sp2 phase transition of the DLC phase; re-crystallization and reorientation of the dichalcogenide phase; change of surface chemistry and structure from amorphous carbon in humid air to hexagonal dichalcogenide in dry nitrogen and vacuum; and sealing the dichalcogenide phase to prevent oxidation. These mechanisms were demonstrated using WC/DLC, TiC/DLC, and WC/DLC/WS2 coatings. The hardness of WC/DLC and TiC/DLC composites was between 27–32 GPa and scratch toughness was 4–5 fold above that of nanocrystalline carbides. The WC/DLC/WS2 composites survived millions of sliding cycles in vacuum and air under 500–1000 MPa loading, and exhibited excellent friction recovery in humid↔dry environmental cycling. Their friction coefficients were about 0.1 in humid air, 0.03 in vacuum, and as low as 0.007 in dry nitrogen. The proposed ‘chameleon’ concept can dramatically increase wear-resistant coating applicability, durability, and reliability.

Review of engineered tribological interfaces for improved boundary lubrication

Article

Mar 2005
TRIBOL INT

Ali Erdemir

Recent advances in smart surface engineering and coating technologies offer unique possibilities for better controlling friction and wear under boundary or marginally lubricated rolling, sliding or rotating contact conditions. Specifically, such coatings can be tailored to meet the increasingly multi-functional application needs of future engine systems by enabling them to operate in lower viscosity oils with reduced sulfur and phosphorous. Using these technologies, researchers have already pioneered the development of a variety of nano-composite and super-hard coatings providing longer tool life in demanding machining and manufacturing applications. The same technologies can also be used in the design and development of novel coating architectures providing lower friction and wear under boundary-lubricated sliding conditions. For example, such coatings can be tailored in a very special way that while one of the phases can favorably react with certain additives in engine oils to result in an ideal chemical boundary film; the other phases can provide super-hardness and hence resists wear and scuffing. Because of their very dense microstructure and high chemical inertness, these coatings can also provide superior protection against oxidation and corrosive attacks in aggressive environments. The use of solid lubricant coatings may also improve the tribological properties of sliding contact interfaces under boundary lubricated sliding conditions. When fluid and boundary films fails or is broken down, such coatings can carry the load and act as a back-up lubricant. Other smart surface technologies such as laser texturing and/or dimpling, laser-glazing and -shotpeening have also become very popular in recent years. In particular, laser texturing of control or coated surfaces have opened up new possibilities for further manipulation of the lubrication regimes in classical Stribeck diagrams. Controlling dimple size, shape, orientation, and density, researchers were able to modify both the width and the height of the boundary lubrication regimes and thus achieve lower friction and wear at sliding and rotating contact interfaces. Overall, smart surface engineering and coating technologies have matured over the years and they now become an integral part of advanced machining and manufacturing applications. They can also be used to meet the increasingly stringent and multi-functional application needs of demanding tribological applications. In this paper, selected examples of recently developed novel surface engineering and coating technologies are introduced, and the fundamental tribological mechanisms that control their friction and wear behavior under boundary lubrication regimes are presented.

Low-friction TiN–MoS2 coatings produced by dc magnetron co-deposition

Article

Oct 1998
SURF COAT TECH

Coatings of the overall composition TiNx(MoSy)z have been produced by dc co-sputter deposition from a single unbalanced magnetron target composed of TiN and MoS2 halves. Compositional variation was obtained by placing stainless steel substrates at various positions with respect to the target. X-ray diffraction and photoelectron spectroscopy showed that the coatings were composed of distinct TiNx and MoSy phases in the form of a nanodispersive system. Pin-on-disk tribometry and nanoindentation demonstrated that coatings with a hardness exceeding 20 GPa and friction coefficients of about 0.1 could be produced by selecting suitable composition and deposition parameters. These coatings show potential for improved endurance with respect to current MoS2-based low-friction coatings and may be suitable for use in severe conditions, for example, as cutting tool coatings for dry machining.

Effect of Substrate Surface Finish on the Lubrication and Failure Mechanisms of Molybdenum Disulfide Films

Article

Jun 1981
Tribol Trans

Robert L. Fusaro

An optical microscope was used to study the lubrication and failure mechanisms of rubbed (burnished) MoS2 films applied to three substrate surface finishes - polished, sanded, and sandblasted - as a function of sliding distance. The lubrication mechanism was the plastic flow of thin films of MoS2 between flat plateaus on the rider and on the metallic substrate. If the substrate was rough, flat plateaus were created during 'run-in' and the MoS2 flowed across them. Wear life was extended by increasing surface roughness since valleys in the roughened substrate served as reservoirs for MoS2 and a deposit site for wear debris. In moist air, the failure mechanism was the transformation of metallic-colored MoS2 films to a black, powdery material that was found by X-ray diffraction to consist primarily of alpha-iron and MoO3 powders. In dry argon, the failure mechanism was the gradual depletion of the MoS2 film from the contact region by transverse flow. Analysis of the wear debris on the wear track at failure showed it consisted mainly of alpha-iron and some residual MoS2. No molybdenum oxides were found.

Jan 2005
123-136

S M Pimenov
V I Konov
T V Kononenko
S V Garnov
A Blatter
M Maillat
U Bogli
V Romano
H P Weber
H E Hintermann
E N Loubnin

S.M. Pimenov, V.I. Konov, T.V. Kononenko, S.V. Garnov, A. Blatter, M. Maillat, U. Bogli, V. Romano, H.P. Weber, H.E. Hintermann, E.N. Loubnin, Laser applications in tribology of hard materials and coatings, New Diamond Front. Carbon Technol. 10 (2005) 123-136.

Hole formation process in laser deep drilling with short and ultrashort pulses

Jan 2002
108-112

T V Kononenko
S M Klimentov
S V Garnov
V I Konov
D Breitling
C Fohl
A Ruf
J Radtke
F Dausinger

T.V. Kononenko, S.M. Klimentov, S.V. Garnov, V.I. Konov, D. Breitling, C. Fohl, A. Ruf, J. Radtke, F. Dausinger, Hole formation process in laser deep drilling with short and ultrashort pulses, in: Proceedings of the SPIE-The International Society for Optical Engineering, vol. 4426, 2002, pp. 108-112.

Laser surface microstructuring to improve tribological systems

Jan 2003
199-211

V Romano
H P Weber
G Dumitru
S Pimenov
T Kononenko
V I Konov
H Haefke
Y Gerbig
M Sentis
J Hermann
S Bruneau
W Marine

V. Romano, H.P. Weber, G. Dumitru, S. Pimenov, T. Kononenko, V.I. Konov, H. Haefke, Y. Gerbig, M. Sentis, J. Hermann, S. Bruneau, W. Marine, Laser surface microstructuring to improve tribological systems, in: Proceedings of the SPIE-The International Society for Optical Engineering, vol. 5121, 2003, pp. 199-211.

Laser surface texturing for adaptive solid lubrication

Abstract

No full-text available

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