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In this study, we explored the effects of abrasive grain size, applied load and sliding speed on the particle distribution density of polytetrafluoroethylene/bronze composite at the worn surface. Wear tests were performed against different sandpapers under varied loads and speeds. Results show that the surface density can be divided into three types, namely, lesser than, close to and more than the original volume fraction value of particle (15%), as the grain size decreases. This finding can be explained by the change in wear mechanisms. Micro-ploughing is the main mechanism of all the abrasive wears. When the grain size is large, the peeling-off of bronze particles occurs. On the contrary, when the grain size is small, the ‘rolling-effect’ of debris happens.

In this work, we present a non-traditional approach to modeling two-body abrasive wear due to the contact between elastomeric tire compounds and road surfaces. In this direction, the process of two-body abrasion between rubber and surface is modeled as a multiscale contact-fracture process. At the microscale, cracks are initiated and grow due to contact stresses. These initiated cracks at the microscale lead to macrocracks that grow as fatigue cracks over long periods resulting in substantial wear volume. This work is limited to modeling the phenomena at the microscale. The computational results are compared with abrasion experiments conducted on the rubber samples based on ASTM DIN 53516 standards.

We compared the tribological behaviors and the tribo-chemical mechanisms of AlMgB14-TiB2 coatings and B4C coatings under lubrication with molybdenum dialkyl-dithiocarbamate (MoDTC). In unidirectional sliding contact, the boride coatings exhibited an unstable tribological performance, while the friction coefficients of these coatings maintained a very steady low level in reciprocating sliding contact. No severe wear occurred to the boride coatings. However, significant abrasive wear was observed on the steel balls rubbing against the boride coatings under unidirectional sliding contact. Analysis indicated incomplete dissociation of MoDTC at coating wear tracks and no formation of MoS2 tribofilms on steel counterfaces in the case of unidirectional sliding contact, whereas well-developed MoS2 tribofilms were formed on AlMgB14-TiB2 coatings under reciprocating sliding condition.

The attention is focused on high-performance Mg alloys due to their favorable biocompatibility, lightweight, physicochemical and mechanical properties. Here, the fretting performance of Mg–Sn–Y alloy was evaluated under fluids lubrication, and the fretting mechanism was explored in detail via analysis of wear track/debris using SEM and XPS depth profile. The results illustrate that the friction reduction is superior to wear resistance for lubricated Mg–Sn–Y/Steel contact under fretting conditions, mainly depending on the oil-film induced transformation of fretting running regime and transition of fretting wear (from adhesive/oxidation wear and delamination under dry friction to abrasive wear and delamination under fluids lubrication). Hence fretting performance of Mg–Sn–Y alloy under fluids lubrication depends on fretting running regime and synergy of oil-film/protective film.

New leather treatment processes involving nanoparticles require new testing methods and procedures to evaluate their impact on human health. In the current work, the tribological properties of goat leather surfaces with sputter deposited Ti-Ag-O films were analyzed. A set of different polymer counter bodies was used to establish different tribological contact situations. A detailed analysis of the worn surfaces by scanning electron microscopy revealed details about the wear mechanisms ranging from abrasive to adhesive depending on the friction. Further, information about the formation of wear debris particles from the Ti-Ag-O films was obtained, in particular whether or not these particles were transferred to the counter body. The performed tests exemplify a possible testing procedure for leather treated with nanoparticles.

This study presents a numerical model of the grinding force during rail grinding that considers the influence of the swing angle of the grinding stone on the position of the grinding area. The numerical model of movement process and material removal of single abrasive grain at different swing angles are established. The surface characteristics of the grinding stones, such as protrusion heights and density of grains, are measured to establish the model of grinding force in the whole grinding area. The results indicate that the grinding forces increase with the grinding pressure and forward speed. In contrast, the grinding forces decrease with the increasing rotational speed and grinding stone granularity.

Working in an abrasive particle environment is considered to be the primary cause of a seal failure. The friction behaviour of FKM O-rings was studied under three-body abrasion conditions, as a function of particle homogeneity, and was discussed in detail. Under the non-uniform abrasive particle size condition, only wear scar caused by large-grained particles can be clearly seen. Due to the seal damage extent led by large particles had been aggravated while led by smaller particles had been depressed. This kind of particularity was defined as non-uniform particle size effects, which could be explained partially by various loads that particles sustained in sliding interface. From the present work, the insights on the friction behaviour of seal was understood and reported.

The solid particle erosion of a spherical alumina particle-reinforced epoxy matrix composite was investigated. Three dimensionless parameters were demonstrated to play key roles in the erosion resistance: r1, the ratio of the abrasive to reinforcement particle size; r2, the ratio of the abrasive particle size to the average edge-to-edge distance between reinforcements; and r3, the ratio of the abrasive particle kinetic energy to a threshold kinetic energy. At perpendicular incidence, modest improvements in erosion resistance could be obtained at intermediate r2 values (1

In this work, short carbon fibers were utilized as reinforcing materials to incorporate with C-SiC ceramics. Cf/C-SiC composites containing diverse fiber contents were fabricated by combining compression molding and hot sintering. Mechanical and tribological properties were carefully investigated. The result indicates that 30 vol% fiber content composite shows the highest flexural strength (201.42 MPa) and shear strength (116.68 MPa). The reinforcing mechanisms are summarized as fiber pulling-out, fiber debonding and fiber bridging, as well as crack deflection. Tribological testing reveals that 30% fiber content composite shows the strongest wear resistance (3.95 × 10−6 mm3/N⋅m) and cyclic performances (COF of 0.27 after 50 cycles). The friction mechanisms are divided into abrasive wear, adhesion wear and oxidation wear by different wear stages.

In the present work, dry sliding wear behavior of AZ91 Magnesium alloy with different microstructural conditions are investigated under a set of processing parameters. The investigations are carried out on four material conditions: (i) AZ91 Magnesium alloy, (ii) AZ91 alloy with precipitate, (iii) AZ91 alloy with in-situ TiC + TiB2 reinforcement and (iv) AZ91 alloy with both precipitate and in-situ reinforcement. The effect of microstructural modification on different wear mechanisms namely: abrasive, oxidation, delamination and melt wear is established. The processing windows for all the four types of wear mechanism are established and the wear mechanism maps are also constructed by correlating the microstructures of worn surfaces and test parameters. The inherent mechanisms of all the four types of wear behavior are established for all the material conditions.

Two-body abrasive wear behavior and mechanism of Fe B alloys with different Mo contents have been systematically investigated. The results show that the Mo addition can promote the formation of Mo-rich and Cr-rich M2B in Fe B alloys, and the Mo-rich and Cr-rich M2B possess the higher H (hardness) and δA (plasticity factor) compared to the Fe-rich M2B. Meanwhile, with the increase of Mo content, the VMo+Cr/VFe increases slightly firstly and then increases rapidly (Where the VMo, VCr and VFe represents the volume fractions of Mo-rich, Cr-rich and Fe-rich M2B, respectively, and the VMo+Cr shows the volume fractions of VMo and VCr). The wear results reveal that the wear rate decreases greatly with the increasing VMo+Cr/VFe, especially when the VMo+Cr/VFe B alloys effectively.

In order to improve the friction and wear properties of gray cast iron surface, TaC ceramic layer was prepared by in-situ casting-heat treatment. TaC ceramic layer was analyzed by XRD, SEM and EDS. Hardness of the TaC layer was obtained by nanoindentation. Under the loading of 20 N at room temperature, the friction coefficient values, the wear rate and the wear weight loss of TaC layer were 0.17, 11.3 × 10−5 mm3/Nm and 2.4 mg, respectively. At room temperature, the wear mechanism is dominated by abrasive wear at low load (5 N, 10 N, 15 N), the abrasive wear and slight adhesive wear at high load (20 N). The wear form of TaC layer can be divided into three categories according to the temperature changes.

The influence of grinding pressure on the removal behaviours of rail material was investigated using a rail grinding simulation testing apparatus. Grinding tests were performed at three types of section radius of rail head. The results indicated that with the increase in the grinding pressure, the grinding efficiency was obviously improved and the grinding amount and chip thickness were increased. However, the surface quality became worse and residual stresses were increased. Furthermore, surface burn occurred when the grinding pressure was larger than 1600 N at R13, 1800 N at R80, and 2000 N at R300, respectively. The grinding debris was composed of curled chips, lump chips, and spherical debris. In addition, the wear mechanism of abrasive grains presented macro fracture.

In this reported study, 12 types of spherical convex surface textured thermoplastic polyurethanes (TPU) samples were produced using 3D printing technology to determine if these surfaces could improve the performance and service life of water-lubricated bearings. The wear process of the TPU/QSn7-0.2 friction pairs was analyzed using a specially designed testing apparatus under water-lubricated conditions. As part of the analysis, the friction coefficient, surface topographies, grinding marks and the wear mass from the worn specimens were examined. The analysis results showed that the spherical convex texture effectively improved the tribological properties of the TPU material. The friction coefficients between the friction pair were directly related to the test rotation speed and applied loads. Abrasive wear and adhesive wear were found to be the major wear mechanisms of the non-texture specimen, while the spherical-convex textures appeared to facilitate the removal of friction pair debris from the surfaces, reduced the adhesion between the friction pairs and strengthened the wedge effect and cavitation effects of the water flow. Compared to the non-texture samples, the 1/3 spherical texture samples with an S = 38% exhibited improved tribological properties, and the friction coefficient of these samples was decreased by 64.47% at 0.7 MPa and 250 rpm. These results provide an experimental foundation for the textured design and optimization of the water-lubricated TPU bearing surface.

The cutting mechanism changes back and forth between ploughing-dominated and shearing-dominated in micro-milling of channel. This study was to research the tool wear mechanisms and micro-channels quality using the Ti(C7N3)-based cermet micro-mills in machining Ti-6Al-4V alloy. Tool wear mechanisms contained the adhesive wear, micro-chipping, oxidative wear, flank wear and diffusion wear. However, the abrasive wear was not discovered, which was a distinct wear mechanism with macro-milling. The higher feed rate induced the tool tip temperature and increased workpiece temperature, and the maximum tool tip temperature was 123.6 °C. Moreover, Tool wear of the micro-mill was improved, and the micro-channels quality also enhanced under the feed rate of 1 μm/flute.

Ultra-high molecular weight polyethylene (UHMWPE) is commonly used to make water-lubricated bearing in industrial application. The Water-lubricated bearing components often experience boundary and mixed lubrication during operation, which induces the aging of UHMWPE material, affecting the mechanical and tribological properties of UHMWPE. This investigation aims to study how the wear resistance of UHMWPE is affected by aging. A CBZ-1 tribo-tester was used to conduct the sliding wear tests between UHMWPE pins and ZCuSn10Zn2 discs rubbing pair under water lubrication. The comparison analyses of the shore hardness, friction coefficients, wear mass loss and worn surface morphologies were elevated. Also, the Raman spectrum, Infrared spectrum and the change of elements of aged UHMWPE samples were examined. The results showed that the accelerated aging had a significant effect on the mechanical and tribological properties of UHMWPE. Especially, compared with the original sample the average friction coefficient increases by 65.96% under 720 h, 80 °C aging condition. Moreover, accelerated aging also resulted in a fracture of molecular chains and chemical oxidation reaction of UHMWPE, the concentration of O element increased to 12.803% when the aging condition was 720 h, 80 °C, which was closely correlated with the deterioration of its wear resistance. The main wear mechanisms were fatigue wear and abrasive when the aged temperature was 40 °C, 60 °C and the aged time was 120 h, 240 h and 360 h. At the 80 °C, 480 h and 720 h aged conditions, the main wear mechanisms between rubbing pair were adhesin wear and fatigue wear. The knowledge gained herein will be useful for optimizing and designing water-lubricated material in extreme conditions to prolong the service life of water-lubricated bearings.

The vibration of the pipeline act on the gasket sealing surface in the form of fretting wear, reducing the sealing performance. In this paper, an experimental study was described on the fretting wear and frictional mechanism of interface between spiral wound gasket (SWG) and flange. The results showed that the gasket winding structure affects the variation of the friction coefficient fluctuation. Moreover, only the fretting behavior of mixed friction regime (MFR) and slip regime (SR) can be expressed stably. Additionally, fretting wear is dominated by abrasive and adhesive wear, and plastic deformation occurs under high load. The intense wear behavior mainly presented in the circumferential direction of small displacement and the radial friction process of large displacement.

In this paper, the wear performance and mechanisms of PCBN tool in dry hard turning of AISI D2 hardened steel at various hardness levels (40–60 ± 1 HRC) were investigated at a fixed 250-m/min cutting speed, 0.10-mm/r feed, and 0.15-mm depth of cut. The results showed that the workpiece hardness has a great influence on the flank wear. The principle wear mechanisms in the flank wear of the PCBN tools are the abrasive wear in the cases of 40–55 ± 1 HRC, and abrasive and delamination wear in a case of 60 ± 1 HRC due to an abrupt increase of friction at tool-workpiece interfaces, while the crater is the principle wear in the rake face of PCBN tools.

The development of alternative compositions instead of hazard asbestos based materials, in brake pad application, is crucial. In the present study, the asbestos free friction materials were prepared using natural waste ingredients. A variety of banana peel and Bagasse fiber/particle content as a functional/friction additives and nano-alumina particles as an abrasive were used to achieve an optimized friction materials composition. Then, the prepared samples were investigated about microstructure, density, hardness, wear and friction behavior. The results showed, an increase in natural wastes addition lead to a decrease in composites’ density. The dynamometery wear/friction test results revealed the conventional feature of wear surface, including 1st and 2nd plateaue and wear debris. Also, the specific wear coefficients of samples with natural waste ingredients are in order of 10−7 and the friction coefficients are about 0.3–0.4. The composite sample with 5 wt % of bagasse fiber/particle and 5 wt % of nanoalumina particle had the optimized condition among investigating samples with specific wear coefficient of 1.18 *10−7 and friction coefficient of 0.369.

Abrasive particle wear in corrosive environments is very common in offshore industry, e.g., dredging. The synergy or mutual effects between the abrasive and corrosive wear on material degradation cannot be quantified with standard tribological test equipment. A novel test rig has been developed, which couples pin abrasion test set-up (ASTM G132) along with three-electrode electrochemical system that allows to quantify experimentally the synergy between two-body multiple asperity abrasion and corrosion of metallic materials. The present article explains in detail the design and construction of this novel tribocorrosion test rig and discusses the results of investigation on an abrasion resistant martensitic steel in the presence and absence of corrosive medium resulting in higher wear in the latter condition.

NiTi alloys with different porosities were obtained by the Spark Plasma Sintering method. The two-way shape memory effect of NiTi alloys with good integrated performance was obtained by the thermal-mechanical cycling training, and it was used to endow NiTi alloy with the self-adaptive behavior. The results show that the porous NiTi alloys with excellent tribological performances and functional properties were obtained. With the storage of oil, the friction coefficient can decrease from 0.391 to 0.041. The self-lubricating mechanism is the formation of a fractionated thin film, and the main wear form is abrasive wear. The lubricating oil inside the specimens with self-adaptive behavior can be squeezed out or stored back, so as to accommodate the lubricating film for better lubrication.

The ultra-high molecular weight polyethylene (UHMWPE) has become one of the most popular and reliable material for water-lubricated bearings in recent years. In this study, three kinds of new Koch snowflake textures were designed on the surface of the UHMWPE to try to decrease friction and prolong the service life of the bearings. The wear process of the UHMWPE/QSn7-0.2 rubbing pair was analyzed using a specially designed tester under water-lubricated conditions. The analysis results demonstrated the testing velocity and load significantly affected the friction coefficient of the UHMWPE specimens. The UHMWPE specimen without texture-treatment had higher friction coefficient than that of the textured UHMWPE specimens at high velocity, where the maximum rate of increase was 35.2% at the velocity of 350r/min compared with non-texture. The dominant wear mechanism was abrasive wear and slight adhesive wear for the non-texture UHMWPE sample, and the wear mechanism of textured samples was slight abrasive wear. The wear performance of the UHMWPE with composite texture was superior to that of other textures, which was mainly attributed to the micro hydrodynamic bearing effect and stepped bearing effect. As a result, the findings of this work can provide experimental foundation for texture design and optimization on UHMWPE surfaces for better service of the marine water-lubricated bearings.

Wear behaviour of Al1100- coconut shell ash (CSA) composites at high temperature is investigated. The composites such as Al-5%CSA, Al-10%CSA and Al-15%CSA is prepared, using stir casting technique. The specific strength of Al-15%CSA alloy composite is enhanced by 70% over Al-1100 base alloy. Regression analysis has enabled to quantify slopes of all the materials. While the pressure exceeds the critical value, abrasion increases rapidly, resulting in adhesive wear. When, the temperature increases, the coefficient of friction initially increases up to 6 N/mm2 and then decreases due to the presence of oxides in debris, which are liberated from tribo surfaces. XRD and EDAX analyses have revealed presence of oxide phases in the debris. SEM micrographs have confirmed abrasive nature of wear.

Corrosion, wear and tribocorrosion behaviours of leaded tin bronze were examined in simulated seawater using alumina counterbody for tribological contact. Active dissolution of alloy and corrosion product development on surfaces were the dominant corrosion mechanisms. Tribological contact with counterbody removed majority of the products, thus contributing to active dissolution of freshly exposed surface. This wear-induced corrosion mechanism contributed to 45% and 60% of total material losses at the two highest potentials, 50 mV and 250 mV vs. Ag/AgCl. Pure wear of alloy occurred in the form of abrasive wear. At anodic potentials under tribological contact, corrosion raised the friction coefficient as compared to pure wear and increased wear of the alloy. These results are presented and discussed in this paper.

The wear properties of copper and copper silicon carbide composites processed by powder metallurgy (PM) and high-pressure torsion (HPT) under different sliding distances and applied loads by using dry reciprocated sliding wear test were investigated. HPT improves wear resistance obviously not only relative to PM samples and but also to results previously noted for different Cu composites. The grain refinement with the formation of bimodal and trimodal microstructures after HPT processing improves the wear properties. Wear mechanism depends mainly on material processing method, it converted from adhesive, delamination in the case of PM samples into abrasive wear after HPT. X-ray spectroscopy (EDS) analysis and surface morphology observations of the worn samples and WC ball prove and support the wear results.

Wear behaviour of white cast irons (WCIs) is largely attributable to the particulate-reinforced composite phenomenon, in which both reinforcing particles and matrix play important roles. In high-Cr WCIs, matrix properties are influenced by chromium-to-carbon (Cr:C) ratio. Without a strong matrix, the carbides would not have sufficient support during the abrasion interactions. The effects of Cr:C ratio on the wear properties of plain-Cr WCIs have been only partially studied; but its effect on Nb-containing WCIs has never been explored. This work studies the influence of Cr:C ratio on high-stress abrasion performance of WCIs further reinforced by niobium carbides (NbC). The alloys covered wide range of Cr:C ratios, resulting in considerable variation in hardness — low hardness for both very-low and very-high Cr:C. Abrasion resistance was assessed by the ball mill abrasion test in quartzite and basalt, showing an optimum matrix Cr:C around 14.6 and 18, respectively. The very-high Cr:C alloy exhibited poorest resistance in both abrasives, and the very-low Cr:C alloy was second-poorest. SEM of worn surfaces revealed the effects of Cr:C ratio on the type and level of damages to microstructure, manifested by various morphologies and depths of indentations and grooves on the matrix, and various types and severities of damages to Cr-rich carbides, including micro-cutting and micro-fracture. NbC particles appeared to be protective across the full range of Cr:C ratios.

Head rice grain has a high edible quality, while rice milling process produces lots of broken rice, mainly due to pressure and friction work. In this work, based on the structural properties of brown rice, a developed friction tester was used to analyze the tribological behavior of brown rice. Test results show that rice starch granules have a loose, polyhedral structure, which produce cracks easily and increases the abrasion of brown rice. Three kinds of brown rice show different fracture behaviors. Different friction behaviors appear with rice and milling iron kind, main rice wear mechanisms include fatigue damage, plastic deformation, adhesive wear and abrasive wear. It shows that the study provides a method to understand rice milling mechanism and has a positive influence on selection of materials and parameters for rice milling.

PAO40@SiO2 microcapsules (PSMS) were prepared by adsorbing Poly α-olefin lubricating oil 40# (PAO40) with hollowed SiO2 particles. The tribological properties of polytetrafluoroethylene (PTFE)/aramid fabric composites at different microcapsules contents were evaluated by the ring-block tests. The friction coefficient and wear rate of PTFE/aramid fabric composites containing 6 wt.% PSMS (Fabric-6% PSMS) were reduced by 42.9% and 31.5% respectively, as opposed to those of neat PTFE/aramid fabric composites (Fabric-0%). The service life of Fabric-6% PSMS under radial pressure of 240 MPa was increased by 5.3 times as compared with that of Fabric-0%. The wear mechanisms of Fabric-6% PSMS revealed that SiO2 particles promoted the formation of metal-F bonds on the shaft surfaces and further improved the abrasive resistance of transfer films.

Determining the friction, wear and damage behaviour of aero engine components under realistic operation conditions is important to improve the long-term reliability and efficiency. A special test rig for single plain bearing bushes of the variable stator vane (VSV) system was designed to investigate these components under engine-like conditions. It is found that four main wear and failure phenomena occur during the testing of VSV bushes. These include heavy abrasive wear on the inner contact area, wear on the flange contact area, plastic deformation and material failure as well as heavy wear and debris on the spindle. Results from polyimide-based plain bearing bushes show that the operational torque and wear rate remain almost constant, as long as no failure of the bush occurs.

The paper discusses the properties of the (Mex,Moy,Al1-(x+y))N coatings, where Me means titanium, zirconium, or chromium. The studies were focused on the phase and elemental compositions of the coatings, and their hardness and adhesive bond strength to the substrate were found. The investigation of the tribological properties found that while at temperature of 400 °C, the lowest value of the adhesion component fadh of the coefficient of friction (COF) was registered for the Ti-TiN-(Ti,Mo,Al)N and Cr-CrN-(Cr,Mo,Al)N coatings, then at temperatures of 550 °C and higher, the lowest value of fadh was observed for the Zr-ZrN-(Zr,Mo,Al)N coating. The study of cutting properties during the turning of steel discovered the best wear resistance of a tool with the Zr-ZrN-(Zr,Mo,Al)N coating. Special attention was paid to the diffusion and oxidation processes in the area of the “coating-material being machined” interface. In the mentioned area, the zones of plastic deformation of the coating, formed under the cutting conditions, were discovered and investigated. The studies reveal that plastic deformation deteriorates the barrier properties of the coating layers with respect to the diffusion of iron. The Zr-ZrN-(Zr,Mo,Al)N coating has a balanced combination of high hardness and relatively low value of fadh, due to which it resists well to abrasive and adhesive-fatigue wear.

To investigate the erosive wear-corrosion behavior of ZTAP ceramic reinforced high chromium cast iron matrix composites in two types of sand at various rotational speeds, the ZTAP/Fe composites were fabricated. The interface characteristics, erosion wear-corrosion and erosive wear mechanism have been investigated in a slurry condition at various erosion rotational speeds. The chemical composition of the matrix material was determined using a spark spectrometer. SEM, TEM, 3D laser scanning microscope and AFM were used to analyze the microstructure characteristics and worn surface morphology of the composites. Furthermore, the wear loss rate and relative erosive wear resistance of ZTAP/Fe composites and Cr15 standard specimen measurements were conducted. The results showed that the interface between the ZTAP ceramics and the Cr15 matrix exhibits a continuous transition layer without visible defects and close contacts. In the case of SiO2 and SiC abrasive sand, the wear rate of ZTAP/Fe composites and Cr15 standard specimens increases with erosion time. The wear rate of ZTAP/Fe against SiO2 sand is lower than that of against SiC sand. ZTAP/Fe composites was found to exhibit a better corrosion resistance property than that of Cr15 standard specimens.

The tribological properties of a Ti6Al4V alloy surface were improved via glow plasma alloying with Co-based alloys. The influence of different target geometries on the thickness of these layers, the sliding and fretting wear resistance as well as the tribological mechanism of the coatings were determined. The low friction coefficient as well as the good fatigue wear, abrasive wear, and adhesive wear resistance of CoCrW layer were attributed to its high toughness, excellent loading capability, appropriate thickness, and high hardness. Furthermore, the CoCrMo layer had lower toughness and loading capability than CoCrW; therefore, the CoCrMo alloyed layer exhibited better sliding wear resistance, but poor fretting wear resistance.

The tribological behaviors of Si3N4/GCr15 tribo-pair under dry rolling-sliding friction condition at different loads were investigated by using a modified rolling-sliding contact device. The pure sliding friction under the same condition was executed as a comparison test. The results showed the friction coefficient and the wear rate at rolling-sliding contact condition were below that at pure sliding contact condition. For the rolling-sliding contact condition, when the loads were 10 N and 20 N, the wear mechanisms of Si3N4/GCr15 tribo-pair were adhesive wear and abrasive wear. Hence, the friction coefficients were higher (0.58 and 0.4 respectively). With the load continuously increased from 30 N to 100 N, the dominant wear mechanisms were the combination of adhesive wear, delamination wear and contact fatigue, and the friction coefficient decreased with an increase in the load. In addition, it also can be seen that the rotational number of the ball showed an increasing trend with the increase of the load with the aid of high-speed camera. At the loads of 30 N and 50 N, a discontinuous tribofilm was formed on the worn surface and the friction coefficients were 032 and 0.23 respectively. At the loads of 70 N and 100 N, the friction coefficients were as low as 0.14 and 0.08, the wear rates of both ball and disk were the order of magnitude of 10−7 mm3N−1m−1, and the worn surfaces were quite smooth with a handful of spalling zone, which can be attributed to the tribo-chemical reaction products. For the pure sliding contact condition, the wear mechanisms of Si3N4/GCr15 tribo-pair were mainly dominated by mechanical wear at the loads of 10 N, 20 N and 30 N, and when the load was 50 N the dominating wear mechanism was tribo-oxidation reaction.

Sand deposition has caused damages to downhole equipment during energy exploitation. The frictional behavior of washing tool against casing under sand condition has been investigated using home-developed tribometer. Experimental results show that friction process has three stages, initial friction, fluctuation friction, stable friction stage. Sand particles get and crush into small during friction process in contact area. The wear rate is inversely related with tool material hardness. The growth rate of tool wear rate decreased with load increasing for surface hardened by small crushed particles indentation, demonstrated by surface morphology and element analysis after test. The wear rate decreased with rotation increasing for more crushed particles indentation. The dominate wear form is abrasive wear and micro-cutting, accompanied with adhesion.

The nanoscale adhesive wear of graphene was studied by molecular dynamics simulation of a diamond tip sliding over a few-layer graphene sheet. We obtained the typical adhesive wear tracks with initial rupture cavity induced by adhesive interaction between the tip and graphene. The coupled interaction, between the formation of interfacial bonds and the breakage of in-plane C-C bonds, leads to the usually observed severe damage of graphene after an adhesive wear process. Moreover, the critical contact pressure for onset of adhesive wear of graphene (∼42 GPa) is much lower than that for abrasive wear (∼94 GPa), which also cannot be correctly approximated by the onset condition for initial rupture of graphene during a loading process (∼76 GPa).

The effect of dual particle size (DPS) reinforcement (fine:coarse in weight ratios of 1:3, 1:1, and 3:1) on wear behaviour of LM30/sillimanite composites is reported. Optical micrographs revealed uniform distribution of particles in the matrix. Al2Si4O10 phase was observed using XRD owing to the interfacial reactions of particle with matrix. Further, high nanohardness values of interface revealed sound particle-matrix bonding. The wear resistance of 15 wt.% DPS composites with weight ratio 3:1 improved by 59% over base alloy. In-addition, the results were comparable with the mathematical model and with cast iron used in brake drum applications. SEM-EDS analysis revealed that at low contact pressure, abrasive/adhesive wear mechanism was dominant, whereas at higher contact pressure delamination wear was dominant.

Tribological behavior of the Al-20Si-5Fe-2Ni alloy and its composite containing 30 wt % copper-coated graphite were investigated at 25–500 °C. The result indicated that the composite showed a significantly decreased wear rate at all test temperatures as compared to the alloy. Owing to the combined effect of solid lubrication and dispersion strengthening provided by the graphite particles and in situ formed Al2Cu intermetallic, the composite can avoid severe adhesive wear up to 500 °C. At 25 °C, the predominant wear mechanism of the composite is abrasive wear, and it transforms to abrasive wear and delamination wear at elevated temperatures.

The friction and abrasive wear of plasma sprayed Al2O3-13TiO2 coating, with and without the addition of graphite was investigated. XPS analysis was used to determine the extent of γ-α Al2O3 phase transformation after wear. γ-α Al2O3 phase transformation had different influence on friction and wear of coatings. Al2O3-13TiO2+15% Ni Graphite coating exhibited lower coefficient of friction and lower abrasive wear rates than Al2O3-13TiO2 coating; the magnitude of decrease was dependent on load. The better abrasive wear resistance and lower coefficient of friction of Al2O3-13TiO2+15% Ni Graphite coating was due to the synergistic effect of self-lubricating film of graphite and tribochemical reactions. The severity of contact could identify transitions in abrasive wear rates, operating wear mechanisms and associated failure modes.

Fe3O4 nanospheres, MoS2 nanospheres and Fe3O4@MoS2 nanocomposites were used as lubricating oil additives for steel/steel contact and dispersed in PAO4 base oil. Tribological behavior and wear mechanisms of the steel/steel contacts were investigated. The results indicate that the friction coefficient increased with the addition of Fe3O4 nanospheres and decreased with the addition of MoS2 nanospheres. Their wear types belonged to abrasive wear and furrow wear respectively. In addition, Fe3O4@MoS2 nanocomposites as lubricating additive had excellent lubricating performance and energy-saving potential due to the formation of a stable adsorbed film and a robust tribo-film on the rubbing surfaces which resulted in a mild furrow wear for steel/steel contact.

A series of turning experiments is conducted on Flake Graphite Iron (FGI), Compacted Graphite Iron (CGI), and Nodular Graphite Iron (NGI) under dry condition. With uncoated carbide inserts, the adhesion layer, covering the entire tool-work interfaces, is formed when cutting CGI and NGI, which reduced flank wear compared to FGI. By contrast, the flank wear on the multilayer-coated inserts, obviously significantly reduced compared to the uncoated inserts, is significantly higher for CGI and NGI compared to FGI. Finite Element Analysis (FEA) is used to estimate the average flank temperature under various cutting conditions, which indicates the elevated cutting temperature with CGI and NGI. With the cutting temperatures from FEA simulations, the observed flank wear for FGI, CGI, and NGI conforms to the two-body abrasive wear model, indicating a common abrasive wear mechanism. Therefore, the main reason for the poor machinabilities of CGI and NGI is the higher cutting temperatures on the cutting tools when cutting CGI and NGI.