Friction Coefficient Of Textured Surface Research Articles

Generation method and antifriction performance evaluation of discrete micro-pit surface texture based on high speed ball-end milling process

Benefiting from the structural characteristics of the ball-end milling cutter and the tool motion characteristics during the cutting process, the high speed ball-end milling process can be directly used to manufacture discrete surface micro-pits texture with different sizes and distributions. The influencing mechanism of the interval and distribution of the micro-pit texture on the antifriction performance was investigated by combining Fluent fluid simulation and reciprocating sliding friction test under oil immersion lubrication condition. Results show that the textured surface with micro-pit features shows obvious antifriction ability. The friction coefficient of textured surface was reduced by 61.5 % compared with that of polished specimens. The interval can influence the oil film bearing capacity and then the antifriction ability. The most significant friction reduction effect was achieved when the micro-pit interval was 900 μm. Additionally, the friction coefficient can be further reduced by optimizing the distribution of the micro-pits. The friction coefficient decreased to 0.121 for the orientation angle 70° condition.

Effect of textured parameters on tribological properties of hydrodynamic journal bearing

PurposeThis study aims to improve the tribological properties of hydrodynamic journal bearing via surface texture, as well as the wear and antifriction mechanisms of textured bearing were represented. It provides a design direction for solving the tribological problem of rotor-bearing system.Design/methodology/approachIn this paper, the variation of surface texture parameters (e.g. texture diameter, d; area density, sp; and depth, hp) were analyzed based on finite difference method. The optimal surface texture parameters were obtained by designing orthogonal experiments, and the relationship between friction and wear properties and microstructure was studied via combining electron probe microanalyzer, scanning electron microscope, X-ray diffractometer and friction and wear testing machine.FindingsDimensionless film pressure P increased as the d increased, whereas P first increased and then decreased as the sp and hp increased, and the maximum P was got as sp = 15% and hp = 25 µm, respectively. The friction coefficient of textured surface with suitable parameters was effectively reduced and the textured surface with the best antifriction effect was 5#. Orthogonal experimental design analysis showed that the influence order of factors on friction coefficient was as follows: sp > sp × d > d > d × hp > hp > sp × hp and the friction coefficient first decreased and then increased as the sp, d and hp increased. In addition, the friction and wear mechanism of textured bearing were three body friction and abrasive wear as the matrix structure and hard phase were a single β phase and Mn5Si3, respectively. While the antifriction mechanism of textured surface was able to store abrasive particles and secondary hydrodynamic lubrication was formed.Originality/valueThe sample with reasonable texture parameter design can effectively reduce friction and wear of hydrodynamic journal bearing without reducing the service life, which can provide a reference for improving the lubrication performance and mechanical efficiency of rotor-bearing system.

Tribological performance and self-lubricating mechanism of the laser-textured surface filled with solid lubricant in rolling friction pair

PurposeThis paper aims to find out the tribological performance and self-lubricating mechanism of the laser-textured surface filled with solid lubricant in rolling friction pair.Design/methodology/approachThe textures on the surfaces of GCr15 bearing steel were produced by acousto-optic Q diode-pumped yttrium aluminum garnet laser with the technology of “single pulse one time, repeating at intervals” and filled with composite solid lubricant. The tribology tests were conducted on the MMW-1A universal friction and wear testing machine.FindingsIt was found that the solid-lubricated micro-textured surface can reduce the friction coefficient effectively. The MoS2/PI composite solid lubricant works better than the single MoS2 solid lubricant, and the ratio of PI/MoS2 + PI at 20 per cent is the best recipe. The friction coefficient of the sample surfaces decreases first and then increases with the increase in texture densities, and a texture density of 19.6 per cent has the best effect on friction reduction. The friction coefficient of the textured surfaces gradually decreases with the increase in both rational speed and load. For the same texture density, the friction coefficient of textured surfaces decreases slightly with the increase in diameter. Furthermore, the mechanism of “rolling-extrusion-accumulation” occurred on the textured surface can collect the solid lubricant, thereby, improve the effect of lubricating and anti-friction.Originality/valueThe results of the experimental studies demonstrated the application prospect of laser surfaces texturing combined with solid lubricant in rolling friction pair.

Influence of Laser Shock Texturing on W9 Steel Surface Friction Property

To improve surface friction property of high speed steel, micro-dent arrays on W9Mo3Cr4V surface were produced by laser shock processing. Friction test was conducted on smooth surface and texturing surface and effect of surface texturing density on friction property was studied. The results show that, under the same condition, friction coefficient of textured surface is lower than smooth surface with dent area density less than 6%, wear mass loss, width and depth of wear scar are smaller; Wear resistance of the surface is the best and the friction coefficient is the smallest when dent area density is 2.2%; Friction coefficient, wear mass loss, width and depth of wear scar increase correspondingly as density of dent area increases when dent area density is more than 2.2%. Abrasive wear and adhesive wear, oxidative wear appear in the wear process. Reasonable control of geometric parameters of surface texturing induced by laser shock processing is helpful to improve friction performance.

Surface Engineering Design of Alumina/Molybdenum Fibrous Monolithic Ceramic to Achieve Continuous Lubrication from Room Temperature to 800 °C

Al2O3/Mo fibrous monolithic ceramics are potential candidates for high-temperature applications because of their excellent high-temperature self-lubricated and fracture properties. This study aims at achieving the good self-lubricating ability at a wide temperature variation from room temperature (RT) to 800 °C and avoiding the abrasive wear of the material at the starting moment of the friction test. Three-dimensional composite-lubricating layers were formed by considering texture pattern as storage dimples and burnishing BaSO4 solid lubricant (SL) on the textured surface of Al2O3/Mo fibrous monolithic ceramics. The friction properties and wear mechanisms were studied from RT to 800 °C in a continuous heating process. The results show that the synergy effect of micro-texture, BaSO4 SL and oxidation products derived from Mo containing MoO3 improved the lubricating performances of the material at each temperature stage, thus realizing continuous lubrication in a wide temperature range. It is demonstrated that the friction coefficient of textured surface coated with BaSO4 SL was kept lower 0.57 when subjected to dry sliding against Al2O3 ceramic pin at the temperature from RT to 800 °C, and it even can be as low as 0.30 at 600 and 800 °C. This work is an extension of study that was previously published in Tribology Letters journal.

Experimental study on the tribological performance of fractal-like textured surface under mixed lubrication conditions

Abstract The effect of surface texturing on reducing friction is studied experimentally in this paper. Two types of fractal-like textures and their corresponding regular distribution textures have been fabricated on the surface of AISI1045 steel using a pulse laser, and reciprocating sliding tests were performed on a variable load tribometer (VLT). Friction coefficient of textured surfaces were investigated under various depths and operating conditions. The results show that surface texturing is important for reducing friction. Compared with untextured surface, the textured surface with a depth of 4.7 μm and sliding speed of 153.3 mm/s can reduce friction coefficient up to 48.3%. The fractal-like textured surface has a more effective friction reduction effect than regular distribution textured surface. Comparison of Sierpinski carpet textured surface and circular-based Sierpinski carpet textured surface was studied, and the conclusion was drawn that friction coefficient of the former is smaller than that of the latter under lower sliding speed, however, the conclusion is just the opposite for high sliding speed.

Surface engineering design of Al2O3/Mo self-lubricating structural ceramics - Part II: Continuous lubrication effects of a three-dimensional lubricating layer at temperatures from 25 to 800 °C

Al2O3/Mo self-lubricating structural ceramics with laminated-structure are potential candidates for high-temperature applications because of their excellent self-lubricating and mechanical performances. This study aims at revealing the mechanisms of how a three-dimensional lubricating layer affects the tribological properties of Al2O3/Mo laminated composites at temperatures from 25 to 800°C. A three-dimensional lubricating layer was formed by considering texture pattern as storage dimples and coating solid lubricants (SLs) on the textured surface of Al2O3/Mo laminated composite. The friction properties and wear mechanisms at temperature from 25 to 800°C in a continuous heating process were studied. It is found that the synergy effect of micro-textures and SLs influence the tribological properties of material. Moreover, the tribochemical reaction of SLs stored in the micro-dimples at high temperature improves the lubricating ability of materials, thus realizing continuous lubrication within a wide temperature range. We demonstrated that the friction coefficient of textured surface that coated with MoS2/CaF2–BaF2 SLs was kept lower than 0.50 when subjected to dry sliding wear against Al2O3 ceramic pin at 25–800°C, and it was even lower than 0.15 and 0.35 at 25–200°C and 800°C, respectively. This work is an extension of studies that were previously published in Wear journal.

Tribological performance of surfaces enhanced by texturing and nitrogen implantation

In this paper, a novel texturing technology by means of electrodepositon is introduced. Textured surface covered with small bumps with the average size of 28μm in diameter and 10μm in height was fabricated. The trough around the bumps acts as the pocket to trap the debris. The nitrogen implantation was used to enhance the tribological properties of textured surfaces. The effects of implanted energy and dose on the structures of coating and tribological performances of textured surfaces were studied. The results show that the formation of Cr2N or CrN depends on the implanted dose. After nitrogen ion implantation, the friction coefficient of textured surface reduced and the wear resistance of textured surface was improved. The wear resistance enhances with increase of implanted dose, and has little to do with implanted energy.

Modulation of dry tribological property of stainless steel by femtosecond laser surface texturing

We reported on the modification of tribological properties of stainless steel by femtosecond laser surface microstructuring. Regular arranged micro-grooved textures with different spacing were produced on the AISI 304L steel surfaces by an 800-nm femtosecond laser. The tribological properties of smooth surface and textured surface were investigated by carrying out reciprocating ball-on-flat tests against Al2O3 ceramic balls under dry friction. Results show that the spacing of micro-grooves had a significant impact on friction coefficient of textured surfaces. Furthermore, the wear behaviors of smooth and textured surface were also investigated. Femtosecond laser surface texturing had a marked potential for modulating friction and wear properties if the micro-grooves were distributed in an appropriate manner.