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The paper investigates sliding friction of the α-Al2O3/α-Al2O3 and α-Fe2O3/α-Fe2O3 contacts by using the spring interfacial potential. It is found that at micronscale the friction properties of the oxides are almost independent of the coarse-graining and are the same in the different sliding directions. Even the hardness contacts friction coefficient shows a decrease with increasing intensity of the normal component of the interfacial interaction force. This result is as an implementation for the previous observations of sliding friction of various materials that showed that a drop of friction coefficient with increasing externally applied normal load has originated from deformation of interfaces or occurrence of debris at contact, indicating an unsteady contact.

We developed a method to simulate the polytetrafluoroethylene (PTFE) tribology by estimating the molecular interaction parameters on the basis of experimental verification. We fitted the molecular interaction parameters between coarse-grained PTFE beads using the iterative Boltzmann inversion method and multi-centered Gaussian-based potentials. The fitting parameters were subsequently validated by comparing an all-atom PTFE model and its corresponding coarse-grained model. A two-layer PTFE friction model was then built on the basis of the estimated parameters to study the effect of normal load on the friction coefficient and wear depth of PTFE. The simulation results showed that the friction coefficient decreases and the wear depth increases as the normal load increases. Moreover, the reasonability of the simulation results was verified through experiments.

There have been insistent demands for effective lubricants as well as additives for reducing friction and wear in various applications. Recently, graphene oxide (GO) and nanodiamond (ND) have been observed to be promising materials to reduce friction and wear in tribological studies. Herein, a novel lubricant has been developed by using GO and ND together as lubricant additives in water in order to enhance tribological performance. The tribopairs employed were Si3N4 balls and Si wafers, and the applied normal load was 5–80 mN. The lowest friction coefficient of approximately 0.03 was obtained for water with 0.1 wt.% GO and 0.5 wt.% ND, while the corresponding depth of wear track was as low as about 5 nm. Analysis of the tribological mechanisms elucidated that the sliding-induced nanostructured tribofilm, the low shearing resistance between graphene sheets, and the possible ball bearing effect of ND all contributed to the remarkable tribological behaviors of the lubricant.

To clarify the unconscious response actions to a friction stimulus applied to a finger, ten participants performed a friction test using their right index finger and a specimen on which a self-assembled monolayer was striped to intentionally change the shear strength. Drastic changes were observed in both normal load and shear strength when a finger slid across the striped surface. Because the rate of change under normal load was negligible as the sliding speed increased, the response action to the friction stimulus appeared to depend on sliding speed.

This paper presents the results of the tribological experiments conducted using an oscillating wear tester under lubricated conditions. Specimen from piston ring slid against counter-specimen from cylinder liner. Various surface textures of cylinder liners resulted from honing and/or plateau honing. Tests were carried out for two normal loads of 100 and 300 N at a temperature of 80 °C, the stroke was 3 mm, the frequency was 10 Hz. Each experiment was divided into four time intervals. During breaks between the particular parts of the test, the surface topography of cylinder liners was measured by a white light interferometer. It was found that an increase in the normal load led to an increase in changes of the liner surface textures.

To investigate the nano-scale scratch and friction behaviors of polycarbonate (PC), atomic force microscopy (AFM) was utilized to conduct the nano-scratch tests under different normal loads with a probe of 20 nm tip radius. Then a probe of 1 nm tip radius was employed for the scanning of scratched surface morphology. The stick-slip phenomena are found for all studied normal load levels. The nano-scratch deformation at different normal loads can be categorized into three modes: sliding on asperities, elastic deformed groove and permanent scratch groove. After the analysis of amplitude-frequency characteristics of friction force, a good correlation is found among scratch deformation, friction force and stick-slip. Those findings can be a good guidance to understand and improve the nano-scratch performance of polymers.

A multifunctional hypothesis of filler selection for PTFE suggests ultralow wear (10−7 mm3/Nm) depends on the filler’s ability to both support the normal load by being large in size and to induce favorable tribochemistry by being weak in aggregate strength. This study is the first to test the independent effects of preferential load support and tribochemistry on PTFE wear by studying the wear reducing properties of a porous GaN fiber, a fully dense SiO2 fiber and microsized GaN particles. The results found the only filler that induce ultralow wear is the GaN fiber which was microns in size and friable under shear stresses. This study reinforces the leading hypothesis that a mechanistic synergy is required for ultralow wear PTFE composites.

Fretting crevice corrosion has become a major concern in orthopedic medical devices when passivating alloys are used alone or in combination. In this work the fretting crevice corrosion response of 316 L stainless steel was investigated when the counterface consisted of different alloys and the effects of potential and normal load were investigated. Fretting initiated crevice corrosion was observed in all stainless steel containing couples, but not in the Ti6Al4V_CoCrMo combination. The coefficient of friction (COF) varied with the applied potential, reaching a maximum of about 0.6–0.7 and decreasing on either side. In summary, normal load and electrode potential have significant effects on fretting crevice corrosion and fretting initiated crevice corrosion of SS316L and its mix-alloy couples.

Many wear failures are caused by a combination of fretting wear and sliding wear. In this study, the torsional fretting and torsional sliding wear properties of CuNiAl against 42CrMo4 were comparatively investigated under dry condition using a flat on flat contact tester. Experimental results showed that the sliding friction coefficients declined more dramatically than the fretting friction coefficients when the normal load increased. The fretting wear rate was lower than the sliding wear rate, which was partly due to the solid lubrication effect of the wear debris and strain hardening of the worn surfaces. The dominant wear mechanisms for the fretting tests were oxidation, cracks and delamination, while for the sliding tests were abrasion combined with plastic deformation.

An effective and simple method is reported to enhance the property and economics of graphene lubricants, that is, 3D porous graphene and T161 are proposed as hybrid lubricant additives. Compared with PAO 6, 3D PG-T161 can reduce the friction coefficient of 316 ASS (Austenitic stainless steel) by about 4.0%, 26.1% and 73.1% respectively under the normal load of 5 N, 50 N and 100 N, and the wear rate is reduced by about 28.9%, 65.6% and 97.8% respectively. The excellent tribological performance is attributed to the formation of uniform protective lubricating film. These findings are of great significance for enhancing the tribological properties of ASS and expanding its application range.

Experiments were carried out using a pin-on-disc tester in conformal contact starved lubrication and unidirectional sliding with constant normal load of 20 N and sliding speed of 0.8 m/s. Different combinations of co-acted samples were studied: textured specimen and untextured counter-specimen, both samples textured and untextured. Samples with the following densities of dimples were tested: 2.25%, 5%, 9%, 14% and 20.25%. The best tribological performance was achieved for both surfaces textured with the smallest pit-area ratio. For large area densities tribological behaviors of sliding pairs with one sample textured were better than those with both samples textured.

This paper presents an investigation into the effect of unexpected overloading on scuffing initiation with a twin-disc test device. An existing twin-disc test device was modified to be suitable for applying overloading dynamically to the disc contact. Three test series including three pairs of discs in each series were subjected to combined normal force and rolling/sliding loading. First a base level for scuffing initiation was defined by increasing the normal load stepwise until failure, while keeping the rolling and sliding between the discs constant. In the subsequent test series, the overload cycles were applied at a significantly lower level in two different patterns leading to scuffing at both an earlier and later stage than was observed for the base level. acceptedVersion

This study is concern with tribocorrosion behaviour of Ti6Al4V-HA biocomposites. The Ti6Al4V composites reinforced with different contents of hydroxyapatite (HA) particles 5–15%, vol%) were produced by hot pressing technique. The tribocorrosion tests were performed by using a ball-on-plate configuration in artificial saliva at 37 °C. The tests were carried out under open circuit potential (OCP), with a sliding duration of 1800 s, 1 N normal load and 1 Hz frequency. The open circuit potential and wear mechanisms for all tested biocomposites are presented and discussed. The results suggest that HA plays a relevant role on tribocorrosion behaviour of Ti6Al4V-HA composites. All composites samples presented better wear resistance and also a relatively lower tendency to corrosion with increasing HA content.

A marker layer (Au80Pd20) combined with four different techniques was used in order to estimate the real contact area between static steel–steel contact pairing (substrate: AISI304 and ball: AISI 52100). The experiments were done with polished references (substrate and ball) and with substrates having a laser-patterned line-like surface topography using two loads (1 and 5 N) and two pattern periodicities (9 and 15 µm). Irrespective of the normal load, all techniques led to the same results within the standard deviation for the polished surfaces. For the laser-patterns, only the combination of foot-printing, scanning electron microscopy and image segmentation is capable to provide meaningful results, since the other techniques significantly overestimate the real contact area.

To determine the effect of thermal aging on the scratch behavior of polymethyl methacrylate (PMMA), the scratch tests of PMMA at different aging time were conducted with the linear progression of the normal load. It was shown that the critical normal load corresponding to the surface crack decreases with the increase of aging time. The supplement indentation test and numerical simulation were conducted to identify the surface crack-initiation strength of the aged PMMA. A good correlation was found between the surface crack-initiation strength and the critical normal load. This implies that the surface crack-initiation strength could be a good criterion to measure the scratch damage of PMMA.

In many engineering environments tribocorrosion is combined with fatigue (multi-degradation). In the present work, the effect of static/cyclic bending and normal load on multi-degradation of austenitic and super duplex stainless steels has been studied. Investigating surface and subsurface characteristics by SEM/FIB, tribologically refined layers (TRL), crack matrices and pits were observed and their role on wear mechanisms was elucidated. Passive film thickness and composition was examined with XPS. Observations showed surface tensions increase the passive film thickness which can control pit and crack matrix formation thus wear loss mechanisms. Static and cyclic bending resulted in thicker oxide layer, enhanced pit formation and wear debris detachment while in the absence of 4-point bending larger subsurface cracks and TRL were observed.

Al-2.26% Mg alloy reinforced with Al3Zr particles was synthesised by Direct Melt Reaction in situ technique. Wear rate, wear rate/vol% Al3Zr (normalised with respect to amount of Al3Zr), normalised wear, and wear coefficient have been evaluated. At different combinations of normal load and sliding velocity two modes of wear i.e. mild/oxidative and severe/oxidative-metallic modes are observed. With increase in the amount of high hardness Al3Zr particles, composites can be used even at higher load and sliding velocity while still being in mild wear regime. Coefficient of friction (COF) has fluctuating tendency with sliding distance. COF shows a decreasing trend with load, whereas, with sliding velocity and composition trend is reversed. Low wear and high COF indicates its suitability in brake materials.

The aim of this work was to investigate the influence of the processing conditions on the tribocorrosion behavior of hot pressed CoCrMo biomedical alloys. Several samples were processed as a function of different processing temperatures (900, 1000 and 1100 °C) and times (10, 30 and 60 min). Tribocorrosion tests were carried out in artificial saliva at 37 °C, under 1 N normal load, 1 Hz frequency and 3 mm stroke length. Open circuit potential was measured. The worn surfaces were inspected by means of SEM/EDS. Results revealed a decrease of wear rate with increasing hot pressing time. The samples hot pressed at 1000 °C revealed the lowest wear rate. These findings showed that the processing conditions play a relevant role on tribocorrosion behavior of CoCrMo.

In this work, we have investigated anisotropic frictional behaviour of patterned silver surfaces. Anisotropy in coefficient of friction (COF) is observed depending on the sliding direction on one-arm and two-arm columnar structures as a function of applied normal load. Anisotropy in COF values for one-arm Ag nanocolumnar surface was observed to be as large as 42% when measured between along and transverse to the columnar tilt direction. However, the percentage change in COF values were as high as 67% for two-arm (zig-zag) nanocolumnar surface along the tilt direction of the columns between trace-retrace directions. There was a significant variation in COF of about 149% by changing geometry from one-arm to two-arm (zig-zag) nanorods, which is explained through a force balance model.

Rail grinding is of vital importance for high-speed railway with safe, reliable and comfortable operation. Here, a self-design grinding machine was applied to evaluate the performance of as-prepared grinding stone (GS) vs Rail under normal loads and grinding speeds. Results illustrate that the increase in normal load leads to the wider and thicker wear debris, but the increasing grinding speed is opposite. Friction-induced heat regulated by working parameters determines the grinding properties of the GSs/Rail contact, high grinding-heat causes the plastic deformation and accelerates the wear. The finite element analysis verifies the source/distribution of grinding-heat and heat flux, thereby revealing the material removal mechanism. It is of great significance for long-term safe and reliable operation of rail via grinding regulation.

This paper studies the friction and wear of Hadfield steel single crystals with the normal load/friction force orientations [ 1 ‾ 1 ‾ 0 ] / [ 1 ‾ 10 ] and [ 1 ‾ 1 ‾ 0 ] /[001]. Due to the different friction force orientation, deformation occurs by twinning in the first case and by slip in the second case. The shear stresses were estimated and correlated with the observed slip band systems. Changes in the orientation of the worn surface were examined by EBSD analysis. TEM studies were performed to investigate the dislocation structure evolution near the worn surface.

To investigate the scratch behavior of short glass fiber (SGF) reinforced polybutylene terephthalate (PBT) composites, the scratch tests with the progressively increasing normal load were conducted for PBT reinforced with 0 wt%, 10 wt%, 20 wt% and 30 wt% SGF. The effect of fiber content and orientation on the scratch behavior of PBT composites and underlying scratch damage mechanisms were investigated. The addition of SGF alters the critical normal loads of onset fish-scale deformation and material removal respectively. The glass fiber fracture was observed and its damage mechanism was analyzed. The results show that although the bulk mechanical properties of PBT are enhanced, the addition of glass fiber generally causes poor scratch resistance. The guidance for designing scratch-resistant SGF reinforced PBT is also discussed.

Experiments were carried out using a pin-on-disc tribological tester in a flat-on-flat configuration in unidirectional sliding. Both counterparts were made from steel with 50 HRC hardness. The normal load was 20 N, the sliding speed was 0.4 m/s, the number of revolutions was 10,000. Before each test, one drop of L-AN-46 oil (0.08 ml) was supplied to the inlet side of the contact zone. The discs were textured using abrasive jet machining. Tribological effects of eight chevron-based textures were compared with that of the surface having circular oil pockets. All textures had the same pit-area ratios and depths. The untextured assembly was also tested for comparison. It was found that chevron-shaped dimples were sensitive to their angular orientation to the direction of sliding. The best tribological performances were achieved for chevrons inclined to the outer sides of the rotating discs.

In the present study, experiments were conducted using an advanced micromechanical apparatus investigating the tribological behavior of interfaces between an organic shale against two different proppant simulants; one composed of Leighton Buzzard sand (LBS) and the other composed of glass beads. A negative correlation was observed between the coefficient of friction and the magnitude of normal load from organic shale-proppant interface shearing tests. At relatively low shearing velocities (0.2–0.4 mm/h) stick-slip shearing behavior was found to be more prominent, and the change of shearing velocity had insignificant influence on the coefficient of friction. Additional discussion is presented comparing these results from the present work with a previously studied inorganic shale.

A systematic experimental study has been conducted to evaluate the sliding tribological properties of CoCrFeNiMo0.2 high entropy alloy at room temperature. The results showed strong dependence of its friction and wear behaviours on sliding duration, normal load and velocity. Increase in load led to decrease of both friction coefficient and specific wear rate, while increase in velocity resulted into decrease of friction coefficient but increase of specific wear rate. Detailed wear mechanisms were investigated by examining the worn surface morphology, chemical composition and its cross-sectional microstructures. The dominant wear mechanisms changed gradually from abrasion and plastic deformation to oxidation wear and delamination with increasing the sliding duration and normal load. Moreover, abrasion and adhesion played the main roles at high sliding velocities.

An innovative in-situ method of generating tungsten disulphide (WS2) tribofilms was proposed in this study. It was found that the WS2 tribofilms formed via a tribochemical reaction between tungsten carbide particles embedded in a steel surface and an extreme pressure lubricant additive led to low friction and significantly improved anti-wear properties in humid air. The presence of the WS2 tribofilms was detected by X-ray Photoelectron Spectroscopy and their chemical surface composition was discussed. The friction behaviour was influenced by the rate of WS2 tribofilms formation, EP additive concentration and normal load applied. Moreover, it was found that the WS2 tribofilms were crucial for significant reduction in friction and negligible wear of WC-functionalized steel surfaces.

The self-lubricating effects of metal matrix self-lubricating composites are based on migrating solid lubricant from matrix to worn surface, which results in the formation of transferred film mainly containing solid lubricant. To explore the migration mechanism of solid lubricant and calculate the thickness of transferred film, an approximate model is developed. The influence of normal load, friction coefficient, volume fraction of solid lubricant and yield strength of solid lubricant are investigated based on the model. A comparison of theoretical and experimental data suggests that theoretical data is in qualitative agreement with experimental data, implying that the model can be expected to give recommendations for designing metal matrix self-lubricating composites.

In this paper, the scratch resistance of injection molded, glass fiber reinforced polycarbonate (PC), constructed with different packing pressures and fiber compositions, was evaluated using the progressive normal load scratch test. The quantitative evaluation of scratch resistance of the samples was based on the onset of visibility and morphological transition points of the scratch for two fiber orientations and various scratch speeds. This study reveals that glass fiber reinforcement exerts a beneficial influence on scratch visibility; however, it has an adverse effect on morphological damage. Anisotropy and heterogeneity of glass fiber reinforced PC also plays a role in scratch resistance. The relationship between the onset of scratch visibility and damage transition points is also discussed.

The influence of the pH in water lubricated sliding contacts was evaluated in terms of friction and wear. The experiments were carried out using a ball-on-disc setup. Si 3 N 4 balls and Al 2 O 3 discs were tested at temperature of (22±2) °C, sliding speed of (1.00±0.03) m/s and normal load of (54.25±0.17) N. Eight types of water with pHs varying from 3 to 12 were used as lubricant. The running-in period, friction coefficient and wear-volume were shown to be nearly independent of the initial pH values within the DLVO range (4≤pH≤10), since at these range the water׳s pH tends to the same value (7.6±0.3) during the test. Superlubricity could be reached with negligible wear by properly setting the electrochemical properties and operating conditions of the tribosystem.

Contact between two highly loaded flat surfaces is examined. In these experiments, a polished, hard metal surface was pressed against a rough aluminium alloy surface. The goal of the experiments was to flatten the peaks on the rough surface by plastic deformation. The experiments elucidated the relation between the normal load and the plasticity index, ψ, and the plastic deformation of the surface roughness peaks in the softer material. The results showed a significant reduction in surface roughness. Increasing the load caused a gradual reduction in the surface peaks. However, based on the values of the plasticity index ψ, it can be concluded that the peaks of the softer material underwent plastic deformation, regardless of the load.

In this paper, the tribological characteristics of Si3N4-hBN ceramic composites sliding against poly-ether-ether-ketone in artificial seawater were investigated, and the normal load was varied from 10 N to 30 N in the step of 10 N to investigate the effect. It can be found that the tribological performance of sliding pair improved with the increasing load. This result was attributed to the complex factor about the polymer characteristics, the seawater environment and tribochemical reaction products. On the other hand, hBN had a magnificent effect on the tribological properties of Si3N4-hBN/PEEK pairs. Especially, SN20/PEEK sliding pair possessed the best tribological performances at the load of 30 N.

In this work, a study of the wear transition regimes was carried out for a pin-on-disk sliding couple, involving two steels of different hardness and Cr contents. Dry sliding wear behaviour of the more highly alloyed stainless steel was dominated by adhesive wear and tribo-oxidation at relatively low sliding speeds and by mixed and adhesive wear at high speeds and loads. In contrast, oxidative wear was more predominant for the lower alloyed steel. The individual wear maps generated for the individual components i.e. material and counterface are discussed in the context of the wear mechanisms observed in the tribological contact.

In this study, the influence of bulges around the dimples rim on the sliding friction and wear behavior was investigated. The objective of this study is to gain a better understanding of the influence of bulges on the sliding friction and wear at various normal loads and reciprocating speeds. The experimental test results showed that the friction coefficient and wear rate of the dimpled specimen with bulges were lower compared to that of the polished specimen, which may be attributed to the reduced contact area. Also, it was found that both sliding friction and wear behavior strongly depend on the sliding speed and normal load. The mechanisms of friction coefficient reduction and wear resistance enhancement were studied and discussed quantitatively.

Bending fretting fatigue tests of 7075 aluminum alloy cylinders against 52100 steel cylinders orthogonally have been carried out under a same normal load and varied bending loads. The S–N curve of the bending fretting fatigue showed a characteristic of “C curve”. Based on the OM, SEM, and TEM, the fretting fatigue damages of 7075 alloy have been analyzed in detail. A physical model was set up to describe the surface damage and the crack formation process in MFR. The TEM analyses showed that the stress concentration at the wall of dislocation cells was the reason of the fatigue crack initiation.

We focus our study on belt finishing process using a 3D model with multi-asperity abrasive wear on real rough surfaces. The established model allows determining the effect of the local geometry of abrasive grain on the friction coefficient and wear rate. This study shows that the friction coefficient and wear rate increase with the local slopes of the roughness. With the increase of the macroscopic normal load, the wear rate increases rapidly. Such effect is related to the increase of the cutting force of each grain leading to the transition in dominant wear mode from ploughing to wedging and cutting.

Microscratch tests were carried out on Cu–graphite composites with graphite content of 0–30 vol% and normal loads of 0.5–2 N. Scratch grooves generated by the plastic deformation of surfaces were characterized for detailed friction and wear mechanisms investigation. The influence of normal load and graphite content on friction coefficient was also studied. It is found that the dominant wear mechanism transits from ploughing to micro-cutting with increasing the normal loads. A friction model for knowing the contribution of ploughing and adhesion components to friction is presented. This friction model is useful in understanding the friction mechanism of composites during scratching.

Scratch resistance and tribological properties of hydrogenated and hydrogen free diamond like carbon (DLC) coatings were investigated in ambient atmosphere under unlubricated and lubricated conditions using layers of oleic (C18H34O2) and linoleic acid (C18H32O2). Scratch resistance property improved in hydrogenated DLC while using linoelic and oleic acids compared to unlubricated condition. Coefficient of friction (CoF) was found to decrease under ambient dry conditions, while under lubrication condition, it was found to increase with normal load. At low load of 1 N, hydrogenated and hydrogen-free coatings show a super low CoF of 0.001 and high wear resistance with oleic acid.

In this work, the frictional behaviors of carbon nanotubes under various sliding conditions were investigated using Molecular Dynamics Simulation. A single CNT and multiple aligned CNTs were modeled for friction simulation under a normal load ranging from 3 nN to 32 nN. Three sliding directions were chosen to investigate the effects of orientation. Results showed that a lower friction coefficient was obtained under high normal loads for all cases. When a single nanotube was used, the friction coefficient along the 0° direction was the smallest, while simulations with multiple aligned CNTs exhibited the smallest friction coefficient along the 90° direction.

A scratch test was performed on poly(methyl methacrylate) (PMMA) material that had been optimised for electronic products. In this study, the scratch properties of PMMA containing various concentrations of slip agent were investigated by performing scratch tests under two different load conditions, i.e., a static normal load and a variable normal load. The effects of the concentration of slip agent on the scratch properties of PMMA were characterised by some key tribological parameters, based on a new standard test methodology. Additionally, the damaged surfaces of the specimens were investigated to understand the variations in scratch mechanisms.

Bending fretting fatigue tests of 316L austenitic stainless steel plates against 52100 steel cylinders have been carried out under same normal load and varied bending loads. Tests of plain bending fatigue were carried out as a control group. The S – N curves of the bending fatigue were made. The results indicated that there was an obvious drop of life under the condition of bending fretting fatigue due to higher local contact stress. A dislocation model of micro-crack nucleation mechanism, as a manner of zig-zag mode, was created to explain the nucleation of fretting fatigue cracks.

The tribosystem consisted of a stationary block pressed at a required load P against a ring rotating at a defined speed. Sliding was unidirectional. Block samples, made from bronze CuSn10P with 138-HB hardness, were modified using a burnishing technique to obtain surfaces with circular oil pockets. Rings were made from 42CrMo4 steel, of hardness 40 HRC, which was obtained after heat treatment. Tests were conducted at a constant speed of 0.27 m/s. Before the test, an oil drop was added to lubricate sliding surfaces. A seizure resistance test was carried out at constant normal load of 2700 N. Tribotests were automatically stopped when the coefficient of friction reached a limit value 0.15. Selected textured samples clearly exhibited a lifetime longer than untextured reference specimens.

Wear behavior of the HVOF deposited Cr 3 C 2 -NiCr and WC-Co coatings on Fe-base steels were evaluated by the pin-on-disc mechanism. The constant normal load applied to the pin was 49N and sliding distance was 4500 m with velocity of 1 m/s, at ambient temperature and humidity. The specific wear rate of WC-Co coating was 3 mm 3 /N m and Cr 3 C 2 -NiCr coating was 5.3 mm 3 /N m. SEM/EDAX and XRD techniques were used to analyze the worn out surface and wear debris. The Fe 2 O 3 was identified as the major phase in the wear debris. The wear mechanism is mild adhesive wear in nature.

This paper presents an experimental study on the block-on-cylinder wear behavior of an electroplated Ni–P coating immersed in 5% NaCl solution at different temperatures and polarization potentials. The simply immersion corrosion without normal load was performed first, and then the corrosion effect on the wear behavior including friction coefficient, surface roughness and weight loss were discussed. It is found that the morphology nature of the corrosion film has crucial effect on the wear performance of the coating. Moreover, the bath temperature and the polarization potential greatly influence the formation of the corrosion film.

This study focuses on the transition from mild to severe wear in the wheel and rail contact. Such a transition has been observed at increased loading (normal load, sliding velocity, or bulk tempera ...

The wear mechanisms of chopped strand mat (CSM) glass fibre reinforced polyester (CGRP) composite subjected to dry sliding against smooth stainless steel counterface (Ra=0.06 mm) were studied using a pin-on-disc technique. The effects of normal load (30–90N), sliding velocity (2.8–3.9m/s) and sliding distance (0.7–3.5km) on friction and wear behaviour of the CGRP composite in two different CSM orientations (parallel and anti-parallel) were measured. The worn surfaces of the CGRP composite specimens for each specific test condition were examined using scanning electron microscopy (SEM). Sliding in P-orientation exhibited lower friction coefficient at lower load and higher speed compared to AP-orientation. Meanwhile, sliding in AP-orientation exhibited (15%) less friction coefficient at higher load compared to P-orientation. At higher range of all tested parameters, AP-orientation exhibited less mass loss (16%) compared to the P-orientation. Interestingly, SEM observations showed various wear mechanisms that predominated by abrasive nature. Damage of different features in the matrix and CSM glass fibre associated with higher values of load, speed, and sliding distance such as micro- and macrocracks in the matrix, interface separation, fibre debonding and fracture, and different sizes of fractured fibres were evident.

Tribological behavior of stir-cast $Al-Si/SiC_p$ composites against automobile brake pad material was studied using Pin-on-Disc tribo-tester. The Al-metal matrix composite (Al-MMC) material was used as disc, whereas the brake pad material forms the pin. It has been found that both wear rate and friction coefficient vary with both applied normal load and sliding speed. With increase in the applied normal load, the wear rate was observed to increase whereas the friction coefficient decreases. However, both the wear rate and friction coefficients were observed to vary proportionally with the sliding speed. During the wear tests, formation of a tribo-layer was observed, presence of which can affect the wear behavior, apart from acting as a source of wear debris. Tribo-layer formed over the worn disc surfaces was found to be heterogeneous in nature. Morphology and topography of worn surfaces and debris were studied using scanning electron microscope (SEM). Chemical composition of different wear products was obtained using electron probe micro analyzer (EPMA) and X-ray diffraction (XRD) techniques. Possible wear mechanisms operative in Al-MMC-brake pad tribo-couple have been discussed.