Oil-lubricated Conditions Research Articles

Tribological and vibrational effects of laser surface texturing on steel-steel sliding contact

Laser surface texturing (LST) not only can significantly improve the tribological performance of various tribological contacts, but also can significantly reduce the frictional noise and vibrations generated from sliding contacts. In order to investigate the tribological effect of laser surface texturing, sixteen stainless steel specimens with different surface textures, and different textured area ratios are designed and processed on the surfaces of specimens by means of laser surface texturing technique. Four different operation speeds are carried out using a standard friction and wear testing machine (UMT-TriboLab) under rich oil lubrication condition. The experimental results show that the diameter of surface circular dimple had the most significant effect on the tribological properties of steel-steel sliding contacts, followed by texture depth, texture area density, and sliding speed. The effect of laser surface texturing on the frictional noise and vibration generated from steel-steel in dry sliding contacts is also investigated. Laser surface texture has significant effect on the reduction of noise generated from steel-steel dry sliding contacts in both time and frequency domains. The conclusion is that laser surface texturing has significant effects on the tribological, vibrational, and other physical performance of functional surfaces. To get the best tribological and vibrational performance, the functional surface texture should be optimized considering the coupled effects of surface texture, lubrication, and contact condition.

Frictional wear performance under oil-lubricated conditions and wear resistance mechanism of high-velocity arc-sprayed FeNiCrAl coating

To expand the application of Fe-Al intermetallic compounds in abrasion-resistant coatings and improve the room-temperature brittleness of Fe-Al alloys, FeNiCrAl cored wires based on an Fe-Al alloy for high-velocity arc spraying were manufactured in this study. To further study the friction and wear characteristics of the resulting high-velocity arc-sprayed FeNiCrAl coating, a 3Cr13 coating was selected as a comparison material. Friction tests at various loads (20 N, 50 N, and100 N) were conducted using a UMT-3 multifunctional friction and wear tester under oil-lubricated conditions, and an X-ray diffractometer, a hardness tester, a laser scanning microscope, and a scanning electron microscope (SEM) combined with energy-dispersive spectroscopy (EDS) were used to analyze the friction coefficient variations, phase compositions, Vickers hardness, microstructures, and friction surface morphologies of the two coatings. The results indicate that the friction coefficient of the FeNiCrAl coating is less than that of the 3Cr13 coating under the same conditions. The wear rate variation of the FeNiCrAl coating is smaller than that of 3Cr13 as the load increases. The FeNiCrAl coating mainly exhibits plowing wear at low loads; as the load increases, the pressure on the plowing regions extrudes the material and generates slight peeling wear. The FeNiCrAl coating has superior abrasion performance because dense iron oxide, along with both Fe3Al and Al2O3 oxide films, forms on the friction surface. Furthermore, the FeNiCrAl coating has superior hardness, covers the friction surface, and improves the coating abrasion performance.

Tribological properties and lubrication mechanism of in situ graphene-nickel matrix composite impregnated with lubricating oil

A solid-liquid synergetic lubricating system has been designed to develop a novel self-lubricating nickel matrix composite. The graphene-nickel (G-Ni) matrix composite with porous structure was fabricated by in situ growing graphene in bulk nickel using a powder metallurgy method. The porous structures of the composite were used to store polyalphaolefin (PAO) oil for self-lubricating. It is found that the G-Ni matrix composite under oil lubrication condition exhibited superior tribological properties as compared to pure nickel and the composite under dry sliding condition. The prestored oil was released from pores to the sliding surface forming a lubricating oil film during friction process. This lubricating oil film can protect the worn surface from severe oxidation, and help the formation and transfer of a carbon-based solid tribofilm derived from graphene and lubricating oil. This solid (graphene)-liquid (oil) synergistic lubricating mechanism is responsible for the reduction of friction coefficient and improvement of wear resistance of the in situ fabricated G-Ni matrix composite.

Friction and wear behaviors of a gradient nano-grained AISI 316L stainless steel under dry and oil-lubricated conditions

A gradient nano-grained (GNG) surface layer was fabricated on an AISI 316L stainless steel (SS) by using the surface mechanical rolling treatment (SMRT). Reciprocating dry and oil-lubricated sliding tests of the GNG 316L SS in air at room temperature were conducted in comparison with the coarse-grained (CG) counterpart. Worn surface morphologies and subsurface microstructures were investigated for both 316L SS samples. 316L SS with a GNG surface layer shows a significantly improved wear resistance, especially under oil-lubricated condition. The notably wear resistance enhancement of the GNG 316L SS is attributed to the GNG surface layer with high strain accommodation ability and high hardness, which can reduce the wear volume in the running-in stage effectively.

Determination of friction law in metal forming under oil-lubricated condition

Frictional behaviour under oil-lubricated conditions is studied in compression of a steel sheet by a DLC coated tool. The average frictional stress increases linearly with the average pressure first, then decreases and finally increases linearly again. This tendency is not affected by the lubricant viscosity, lubricant thickness and the stress state of the specimen. It is concluded that the decrease of the frictional stress with increasing average pressure is due to the decrease of the ratio of real contact area, which is caused by the lubricant pressure in closed pools. A new law of friction under oil-lubricated condition is proposed.

Comparative investigation on the wear and friction behaviors of carbon fiber reinforced polymer composites under dry sliding, oil lubrication and inert gas environment

CFRP (Carbon fibre reinforced polymer) composites are applicable for different engineering machinery to perform in different types of adjoining environments. Tribological properties of CFRP composites were examined experimentally and compared in three types of environmentalconditions, (i) dry condition, (ii) oil-lubricated condition and (iii) inert gas (argon). A steel disc of En 31 with hardness of 60 HRC was used as thecounterface. The experiment was done at different sliding speedsand different normal loads. It was observed from the results that sliding in an inert gas environment gives the highest value of friction coefficient followed by dry sliding and oil-lubricated sliding. SEM study of the wornout surfaces shows that the greater wear during inert gas environment results due to an easy detachment of fibres from matrix material.

Tribological Properties of Surface-Textured and Plasma-Nitrided Pure Titanium Under Oil Lubrication Condition

Plasma nitriding was conducted as post-treatment for surface texture on pure titanium to obtain a continuous nitriding layer. Supersonic fine particles bombarding (SFPB) was carried out to prepare surface texture. The surface morphologies and chemical composition were analyzed using scanning electron microscope and energy disperse spectroscopy. The microstructures of modified layers were characterized by transmission electron microscope. The tribological properties of surface-textured and duplex-treated pure titanium under oil lubrication condition were systematically investigated in the ball-on-plate reciprocating mode. The effects of applied load and sliding velocity on the tribological behavior were analyzed. The results show that after duplex treatments, the grains size in modified layer becomes slightly larger, and hardness is obviously improved. Wear resistance of duplex-treated pure titanium is significantly improved referenced to untreated and surface-textured pure titanium, which is 3.22 times as much as untreated pure titanium and 2.15 times of that for surface-textured pure titanium, respectively.

A comparative study of the friction and wear performance of Fe-based bulk metallic glass under different conditions

PurposeThis study aims to compare the friction and wear behaviors of Fe68.3C6.9Si2.5 B6.7P8.8Cr2.2Al2.1Mo2.5 bulk metallic glass (BMG) under sliding using dry, deionized water-lubricated and oil-lubricated conditions. The comparison was performed using a unidirectional ball-on-flat tribometer under different applied loads, and the results were compared to the properties of a conventional material, SUJ2. Fe-based BMG materials have recently been attracting a great deal of attention for prospective engineering applications.Design/methodology/approachAs a part of the development of Fe-based BMGs that can be cost-effectively produced in large quantities, an Fe-based BMG Fe68.8C7.0Si3.5B5.0P9.6 Cr2.1Mo2.0Al2.0 with high glass forming ability was fabricated. In the present study, the friction and wear properties of Fe-based BMG has been comparatively evaluated under dry sliding, deionized water- and oil-lubricated conditions using a unidirectional ball-on-flat tribometer under different applied loads, and the results were compared to the properties of conventional material SUJ2.FindingsThe results show that the Fe-based BMG had better friction performance than the conventional material. Both the friction coefficient and wear mass loss increased with increasing load. The sliding wear mechanism of the BMG changed with the sliding conditions. Under dry sliding conditions, the wear scar of the Fe-based BMG was characterized by abrasive wear, plastic deformation, micro-cracks and peeling-off wear. Under water- and oil-lubricated conditions, the wear scar was mainly characterized by abrasive wear and micro-cutting.Originality/valueIn this investigation, the authors developed a new BMG alloy Fe68.8C7.0Si3.5B5.0P9.6Cr2.1Mo2.0Al2.0 to improve the friction and wear performance under dry sliding, deionized water- and oil- lubricated conditions.

Effect of different levels of free water in oil on the fretting wear of nickel-aluminum bronze based composites

Fretting wear of nickel-aluminum bronze (NAB) alloys and 15wt% Ti3SiC2/NAB composites against the 42CrMo4 steel was studied through flat-on-flat testing at oil-lubrication conditions with varying free-water contents (0, 26.8, 52.3 and 76.7wt%). Tribological test results revealed that the addition of Ti3SiC2 substantially reduced the fretting wear and the friction coefficient of NAB alloys at all testing conditions, which could be attributed to high absorption of the fracture energy on the wear track by the deflection of fatigue cracks along Ti3SiC2/NAB interfaces. In addition, microstructural analyses and dissipative particle dynamics simulations revealed that high free-water contents facilitated the propagation of cracks and break of the oil film, which resulted in the transformation of wear mechanisms from abrasion and mild oxidation at the low free-water contents to abrasion, deformation and oxidation at the high contents. Accordingly, the steady-state friction coefficient of Ti3SiC2/NAB composites increased from 0.09 to 0.17 as the free-water content increased from 0 to 76.7wt%.

Role of Mo on tribological properties of atmospheric plasma-sprayed Mo-NiCrBSi composite coatings under dry and oil-lubricated conditions

NiCrBSi is a material widely used for preparing wear-resistant coatings. In order to study the role of molybdenum (Mo) on tribological performance under dry and oil-lubricated conditions, Mo-NiCrBSi composite coatings were prepared by atmospheric plasma spraying. The contents of Mo in the composite coatings were ranged from 5 to 30 wt.%. X-ray diffraction, optical microscopy and scanning electron microscopy were used to characterize the phase structure and surface morphology of the composite coatings. The tribological performance of the coatings was estimated by reciprocating friction tests. The worn surface was inspected by X-ray photoelectron spectroscopy and energy dispersive spectroscopy to further analyze the wear mechanism. The results showed that the 30 wt.% Mo-NiCrBSi coating exhibited an optimal tribological performance under both the dry and oil-lubricated conditions. The wear resistance of NiCrBSi coating increased when adding 30 wt.% Mo under oil-lubricated condition. It was revealed that MoO2 and MoS2 tribo-films were generated in the friction process under dry condition and oil-lubricated condition, respectively, which accounted for the excellent tribological performance of the composite coatings.

Effect of MoS2 on the tribological properties of carbon fabric composites under wet conditions

Carbon fabric reinforced phenolic composites are very attractive for use as friction materials under wet conditions due to their excellent self-lubricity, wear resistance, and high mechanical strength. However, brittle fracture of carbon fabric bundles during friction is one of the major problems that limit their application. In this work, MoS2 particles were used as additives and friction modifiers to improve the wear and friction behaviors. The composites containing different amounts of MoS2 particulates (0–20 wt%) were fabricated by impregnation technique. The influence of MoS2 on the tribological properties under oil-lubricated conditions has been studied systematically. The experimental results revealed that tribological characteristics such as coefficient of friction and wear resistance were changed significantly with the relative amount of MoS2. Addition of MoS2 within 15 wt% was found to decrease the wear rates of the composites, while 20 wt% MoS2-filled composites exhibited highest wear rate compared to other test samples. Increasing MoS2 content resulted in a rise in the wear rate of the counterparts. Wear mechanisms had been investigated by scanning electron microscope, which could support the observed wear performance.

Effects of Material Combinations on Friction and Wear of PEEK/Steel Pairs under Oil-Lubricated Sliding Contacts

The effects of material combinations on the friction and wear of PEEK/steel pairs are studied using blocks on a ring wear tester under oil-lubricated conditions. The rings are made of forged steel (SF540A) and a PEEK composite filled with 30 wt% carbon fibre. The surface roughness is 0.15 and 0.32 μm Ra, respectively. The blocks are also made of the same materials as the rings: the forged steel and the PEEK composite. Finished with an emery paper of #600, the surface roughness is 0.06 and 0.23 μm Ra, respectively. Sliding tests for 4 combinations of two materials are conducted. The load is increased up to 1177 N at 1 N s-1. The sliding velocity is varied in the range of 10 to 19 m s-1. In some cases, the ring temperature is measured with a thermocouple with a diameter of 0.5 mm, located 1 mm below the frictional surface. Results indicate that the forged steel’s ring and the PEEK composite’s block is the best combination among 4 combinations, because seizure does not occur under the increasing load up to 1177 N at the sliding velocity of 10–19 m s-1. In contrast, seizure occurs at 15 and 19 m s-1 in the other three combinations. However, the PEEK composite’s ring shows a lower friction coefficient as compared to the forged steel’s ring, when seizure does not occur. Wear scars are observed with a scanning electron microscope (SEM). The seizure mechanisms are then discussed.

Hybrid effect of ZnS sub-micrometer particles and reinforcing fibers on tribological performance of polyimide under oil lubrication conditions

In response to the challenges posed by friction and wear of tribo-components exposed to boundary and mixed lubrication conditions, there is increasing interest in the development of polymer-based, self-lubricating composites. This investigation addressed the effect of various fillers (i.e. short carbon fibers (SCF), short glass fibers (SGF), ZnS sub-micrometer particles and combinations of respective fibers with ZnS particles), on the friction and wear of polyimide (PI) when lubricated by poly-alpha-olefins (PAO). A sliding plate-on-ring geometry, using GCr15 steel rings, was used. It was demonstrated that the reinforcing fibers greatly improved the composites’ wear resistance. SGF was observed to be more effective than SCF in respect to friction- and wear-reduction. Moreover, an obvious synergism between SGF and ZnS was identified. The hybrid composite ZnS/SGF/PI exhibited excellent tribological performance under oil lubrication. With respect to the hybrid formulation, the glass fibers imparted their high abrasion resistance to the composite; while ZnS led to complex tribo-chemical reactions. A stable tribofilm consisting of transferred materials and various tribo-chemical products improved the boundary lubrication capability of the sliding system.

Friction and Wear Reduction of Eccentric Journal Bearing Made of Sn-Based Babbitt for Ore Cone Crusher.

An anti-friction Babbitt alloy-coated bearing made by a casting process is a journal bearing, which is used in an ore cone crusher eccentric. The main purpose of the Babbitt coated eccentric is to provide a low friction to support and guide a rotating shaft. Despite the fact that the Babbitt-coated eccentric offers a low friction coefficient and can be operated without a continuous supply of lubricant, it suffers from mining environments and short service life. In this study, an ultrasonic nanocrystalline surface modification (UNSM) technique was used to further reduce the friction coefficient, to increase the wear resistance, and to extend the service life of the Sn-based Babbitt metal. The friction and wear behavior of the Sn-based Babbitt metal was investigated using a block-on-ring tester under both dry and oil-lubricated conditions. The results of the experiments revealed that the friction and wear behavior of Sn-based Babbitt metal could be improved by the application of the UNSM technique. The friction and wear mechanisms of the specimens were explained and discussed in terms of changes in surface properties—microstructure, surface hardness, surface roughness, etc.

Tribological properties of ta-CNx coatings with different nitrogen content under oil lubrication conditions

Carbon nitride (CNx) coatings exhibit a wide range of attractive properties that make them suitable for demanding mechanical and tribological applications. In this study, an ion beam assisted filtered arc deposition (IBA-FAD) method has been developed for the deposition of tetrahedral amorphous carbon nitride (ta-CNx) coatings. The ta-CNx coatings with various nitrogen contents were deposited by controlling the nitrogen flow to investigate the effects of nitrogen content on their tribological behavior. The composition and structure of the ta-CNx coatings were evaluated using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The tribological properties were examined using a ball-on-disk tribo-tester under oil lubrication condition. The results showed that nitrogen contents of ta-CNx coatings were restricted to the range of 0–11at.% by nitrogen ion density. The hardness decreased with an increase in the nitrogen content as nitrogen decreased the fraction of sp3 carbon in the coatings. The ta-CNx coatings exhibit low friction under oil lubrication and the maximum value was obtained for samples containing 8at.% of nitrogen. ta-CNx with 8–11at.% of nitrogen exhibited markedly low wear rate.

Impact of lubrication on the tribological behaviour of PTFE composites for guide rings application

In this study, the friction and wear behaviours of polytetrafluoroethylene (PTFE)-based composites were comparatively evaluated under dry sliding and oil-lubricated conditions. Two PTFE composites filled with bronze and bronze + molybdenum disulfide (MoS2) were considered. These composites were used as guide rings for hydraulic actuating cylinder. Friction and wear tests of the composite specimens sliding against high chromium steel ball were conducted using reciprocating linear tribometer. The wear mechanisms of the composites under the two different sliding conditions were analysed and discussed based on scanning electron microscopic (SEM) examinations of the worn surface and optical micrographs of the steel counterface. Under the oil-lubricated condition, the friction and wear behaviours of the composites were considerably improved if compared to that under the dry sliding. The oil adsorbed layer limited the transfer of the composite to the steel counterface and avoided the oxidation of the MoS2 during the sliding test.

Engineering research of DLC coating in piston pins and bucket tappets

Purpose The purpose of this paper is to study the engineering application of diamond like carbon (DLC) coatings on the surfaces of piston pins and bucket tappets for a 2.0 L supercharged gasoline engine. The friction loss and durability of DLC-coated components were investigated. Design/methodology/approach The tribological characteristics were examined under oil-lubricated conditions in a CETR UMT reciprocating tribometer. In a motored engine test rig, friction loss torque test was performed to estimate the improvement in fuel economy. Fired engine durability bench tests of typical duration of 450 h were completed to access the durability and wear resistance of DLC coating. Before and after durability tests, coated and uncoated components were measured on the sliding surface by a profilometer technique. Findings Friction and wear test results show that DLC coating has low friction coefficient and reduces the wear rates by almost ten times compared to those of uncoated surfaces. Friction loss measurements indicate that DLC-coated tappets can reduce valve train friction loss by 29 per cent, and DLC-coated piston pins can reduce piston group friction by 11 per cent. Based on fired engine durability bench tests, it is evidenced that none of the coated tappets and pins show any noticeable peeling or delamination. Wear profiles analysis results indicate that DLC-coated engine components give rise to a substantial reduction in wear. Originality/value DLC coating applied onto the working surface of piston pin and bucket tappet can effectively reduce the friction loss of gasoline engine. DLC coating exhibits sufficient durability and improves friction and wear performance.

Tribological investigations of glass fiber reinforced epoxy composites under oil lubrication conditions

The tribological performance of short glass fibers (SGF), solid lubricants and silica nanoparticles filled epoxy (EP) composites was investigated under oil lubrication conditions. It is demonstrated that the addition of SGF greatly reduces the friction and wear of EP. However, further addition of solid lubricants and silica nanoparticles does not change obviously the friction and wear. It is identified that the high tribological performance of SGF reinforced EP is related to the high load carrying capacity and abrasion resistance of SGF. The nanostructure of the tribofilm was comprehensively characterized. It is deemed that the tribofilm plays an important role in the tribological performance by avoiding the direct rubbing of the sliding pairs exposed to boundary and mixed lubrication conditions.

Investigation on Wear Resistance and Fatigue Damage of Laser Cladding Coating on Wheel and Rail Materials under the Oil Lubrication Condition

ABSTRACTThe aim of this study is to investigate the wear resistance and fatigue spalling damage of wheel and rail materials with and without laser cladding coating under oil lubrication using a rolling–sliding machine. It illustrates that the laser cladding Co-based alloy coating improves the wear resistance of wheel and rail rollers. Serious spalling is dominant for untreated wheel and rail rollers. The wheel or rail roller undergoing laser cladding treatment takes on slight abrasive wear and visible ploughing. Furthermore, there are no cracks on the contact surface and subsurface. The laser cladding Co-based alloy coating exhibits outstanding resistance to wear and fatigue spalling damage due to its microstructure in the coating under oil lubrication.

Nano patterning of AISI 316L stainless steel with Nonlinear Laser Lithography: Sliding under dry and oil-lubricated conditions

Femtosecond laser-based Nonlinear Laser Lithography (NLL) was applied to AISI 316L stainless steel, which requires surface modification to achieve satisfactory tribological behaviour. NLL advances over the well-known Laser Induced Periodic Surface Structures (LIPSS) in terms of uniformity and long-range order of high speeds, over large areas. A galvanometric scanner head was used for an high production rate. Dry and lubricated sliding tests, considering different orientations of the nanotexture showed that COF values after NLL treatment are significantly lower. In lubricated tests, COF values of NLL-treated surfaces are nearly half the values of untreated surfaces, whereas the difference further increases when measured in dry conditions, where the orientation of the surface texturing influences the results.