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Ti–Al–C–N protective coatings were prepared using laser cladding on the TC4 in this work. MAX phase is generated in situ in the coating. Moreover, as an in-situ autogenous reinforcing phase, MAX phase has good compatibility with the substrate and good bonding force, which is conducive to the full realization of the cladding performance. The results show that the amount of MAX phase increased with the proportion of ceramic phase in the composition design. Among them, the best coating performance is achieved when the component ratio is TiAl: TiN: TiC = 1:1:1. The coating shows the highest hardness of 712–950 HV, which was about twice the hardness of the substrate. It also shows the best resistance to fretting wear at both room temperature and 400 °C. The analysis of the wear mechanism reveals that twins are formed in C1 coatings during fretting wear at both room temperature and 400 °C. The twins not only can rapidly relax the local stress concentration and maintain the plasticity of the material, but also can promote the continuation of slip, and play an obvious strengthening effect without causing serious stress concentration. This work can provide the theoretical basis and data support for the functional-structural integration of protection design of components under actual working conditions. [ABSTRACT FROM AUTHOR]

Fretting wear damage of high-strength titanium fasteners has caused a large number of disastrous accidents. Traditionally, it is believed that both high strength and excellent ductility can reduce fretting wear damage. However, whether strength and ductility are contradictory or not and their appropriate matching strategy under the external applied normal stress (Fw) are still confusing problems. Here, by analyzing the subsurface-microstructure deformation mechanism of several samples containing various α precipitate features, for the first time, we design strategies to improve fretting damage resistance under different matching relation between Fw and the tensile strength of materials (Rm). It is found that when Fw is greater than Rm or Fw is nearly equivalent to Rm, the deformation mechanism mainly manifests as serious grain fragmentation of β and αGB constituents. Homogeneous deformation in large areas only reduces damage to a limited extent. It is crucial to improve the strength to resist cracking and wear, but it is of little significance to improve the ductility. However, when Fw is far less than Rm, coordinated deformation ability reflected by ductility plays a more important role. The deformation mechanism mainly manifests as localized deformation of β and αGB constituents (kinking induced by twinning and spheroidizing). A unique composite structure of nano-grained/lamellar layer and localized deformation transition layer reduces fretting damage by five times compared with a single nano-grained layer. Only when the strength is great enough, improving the plasticity can reduce wear. This study can provide a principle for designing fretting damage resistant alloys. [ABSTRACT FROM AUTHOR]

The influence of electric current pulses passing between parts during fretting wear of titanium alloys is examined. A description of the test bench and a description of the test methodology are given. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study investigates the capability of WC/C coatings to protect bearing bores against fretting wear when there is a lack of lubrication, a typical failure mechanism in bearings subjected to vibrations. Linear pin-on-disc and rotary oscillating block-on-ring tribological tests were carried out reproducing fretting conditions to evaluate the tribological performance and fretting resistance of the developed WC/C coating in comparison with those of the two common coatings currently employed to prevent this type of bearing failure, i.e. thin-dense chrome and fluoropolymer coatings. The friction forces generated under fretting conditions were evaluated, and a deep surface analysis of the tribosystems was carried out through different microscopic techniques in order to identify the wear mechanisms prevailing in each coating. Results suggested that WC/C coatings could be promising candidates to mitigate fretting damage, as they combine a low friction coefficient with good wear resistance. Furthermore, WC/C coatings constitute a more sustainable solution compared to the currently employed PTFE and chrome-based coatings, paving the way to a greener society. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fretting wear is a phenomenon occurring in many engineering objects, including push fit connections. In view of a large number of factors conducive to wear development, it is difficult to describe the mechanism of wear initiation and development. Therefore, various methods are sought to limit wear development. The use of a lubricant may be one of those ways. The aim of this article is to present the results of testing the influence of a lubricant medium on the development of fretting wear in interference fit connections. As a lubricant medium, MoS2 and Whitmore greases were used. For that purpose, wear tests were first conducted on the shaft/sleeve tribological kinematic pair, and then observations and laboratory measurements were performed. The observations demonstrated the presence of fretting wear traces on all tested samples, irrespective of the tribological kinematic pair being tested. The main kind of damage consisted of material build-ups which, during operation, become oxidised and, while moving along the connection, caused local abrasion and micropits. The best results in restricting the development of fretting wear were achieved with Whitmore grease. [ABSTRACT FROM AUTHOR]

The metallic plate is used for bone fixation in biomedical applications, which causes health risks to the patient by leaching ion elements due to the formation of micro-motion between the plate and screw. Currently, the polylactic acid is favoured for replacing metal alloys in temporary implants due to the biodegradable property. However, polylactic acid has low mechanical properties compared to metal alloys and is not preferred as a fixation device. Therefore, the polylactic acid was printed using FDM technique under both horizontal and vertical orientations to improve the mechanical properties. After printing, the samples were post-heat treated at 60℃ for 24 h (B1) and 70℃ for 12 h (B2). Later, compression and fretting wear tests were performed for the printed and post-heat-treated samples to estimate the compression strength and fretting wear. The results indicated that the post-heat-treated horizontal sample B2 obtained a higher compression yield strength of 80.15 ± 3.53 MPa compared to printed and post-treated sample B1. This value lies within the range of bone fixation device. Moreover, a low coefficient of friction (1.34 ± 0.23) was obtained for sample B2 due to the improvement of yield strength. The worn morphology showed that the formation of cracks and spalling was more for the printed and B1 sample compared to the B2 [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fretting wear is the main factor restricting the application of titanium alloy as compressor blades. Preparing a kind of high entropy alloy (HEA) coating is an effective way to improve the fretting wear resistance under high temperature conditions. Thus, in the present work, the FeCrAlMoxNby HEA coating was fabricated on a Ti-64 substrate by the laser cladding technology. The phase composition, microstructure and fretting wear resistance of the coating at high temperatures (200 °C, 300 °C and 400 °C) were investigated. It was demonstrated that the laser cladding FeCrAlMoxNby HEA coatings exhibited dense and uniform microstructures consisting of a BCC phase and a Laves phase (Cr2Nb). In addition, the changing trend of phase content of BCC and Laves phase is the same as the trend of atomic content of Mo and Nb respectively. The presence of the Laves phase increases the hardness of the coating. Due to its high hardness and the formation of a protective oxide layer, the coating demonstrated significantly superior resistance to high-temperature fretting wear compared to the substrate. The lowest wear rate is Mo0·5Nb0.5 coating at 300 °C, only 1.3 × 10−6 mm3/N·m. The current results provide a new method to protect titanium alloy's surface from fretting wear damage in high-temperature service environments.

This study investigates the fretting wear resistance of Inconel 718 fabricated by laser-powder bed fusion (L-PBF) based additive manufacturing (AM) process. A set of the L-PBF processed coupons were subjected to homogenization followed by double aging heat treatment cycles to achieve hardness comparable to wrought material. Material characterization using optical microscopy, scanning electron microscopy (SEM) and x-ray diffraction techniques revealed a fine grained and textured microstructure in AM as-built samples. Point contact (ball-on-flat) fretting wear tests conducted under ambient conditions showed that AM as-built samples had the least wear resistance with a wear coefficient of 15.64 × 10−9 MPa−1 and a higher average coefficient of friction (COF) of 0.75. The wear resistance of the AM samples was found to be improved after heat treatment with the reduced wear coefficient of 10.35 × 10−9 MPa−1 and COF ranged between 0.60 and 0.70. The fretting loops, COF plots and SEM analysis on worn surfaces show that when the applied normal load is low (1N), the operating regime is gross slip regime and the corresponding wear damage is abrasion for all samples. When the load increases to high level (3N), a combined wear mechanism of delamination, adhesion and abrasive wear operating under partial slip regime is predominant with a considerable amount of subsurface cracking. The effect of heat treatment is seen as beneficial in terms of reduction in wear, COF and sub-surface crack which is attributed to improved hardness. [ABSTRACT FROM AUTHOR]

Safety and reliability are the major challenges to face for the development and acceptance of hydrogen technology. It is therefore crucial to deeply study material compatibility, in particular for tribological components that are directly in contact with hydrogen. Some of the most critical parts are sealing materials that need increased safety requirements. In this study, the fretting behavior of several elastomer materials were evaluated against 316L stainless steel in an air and hydrogen environment up to 10 MPa. Several grades of cross-linked hydrogenated acrylonitrile butadiene (HNBR), acrylonitrile butadiene (NBR) and ethylene propylene diene monomer rubbers (EPDM) were investigated. Furthermore, aging experiments were conducted for 7 days under static conditions in 100 MPa of hydrogen followed by rapid gas decompression. Fretting tests revealed that the wear of these compounds is significantly affected by the hydrogen environment compared to air, especially with NBR grades. After the aging experiment, the friction response of the HNBR grades is characterized by increased adhesion due to elastic deformation, leading to partial slip. [ABSTRACT FROM AUTHOR]

Fretting wear in the contact area between the aero-engine blade tenon and turbine disk mortise has an important influence on the performance of the aero-engine. In this paper, the tenon joint structure of the DZ125/FGH99 superalloy material is taken as the research object, and the finite element model of the fir-tree tenon joint structure is established. Through subroutine invocation and mesh adaptive control technology, the fretting wear problem of dissimilar material contact pairs under composite load is numerically studied. The results show that for the specific tenon joint structure and load and boundary conditions studied in this paper, the maximum wear occurs on the contact surface of the first tooth, and the surface will show different partial slip states in different load cycles. The slip region always extends from the two contact edges to the interior, and the upper side has a larger range. Wear has a significant effect on the stress distribution and stick–slip state of the contact surface. The second and third teeth have a small amount of wear and are basically in a stick state during the entire wear process. Therefore, wear has little effect on the stress distribution and the stick–slip state of the contact surface. This study reveals the coupling relationship between the fretting wear and contact state of the tenon joint structure. [ABSTRACT FROM AUTHOR]

The fastener clips of the high-speed railway may fracture due to accumulated fretting damage, posing a hazard to train operation safety. To investigate the evolution mechanism of fretting wear characteristics of high-speed railway fastener clips, this paper conducted fretting wear tests on 60Si2MnA steel used for clips and analyzed the fretting wear characteristics under different number of fretting cycles (N). The results indicate that as N increases, the friction coefficient rises initially, then falls, slightly rises again, and eventually stabilizes. Furthermore, the surface wear volume and depth of 60Si2MnA steel material increase continuously, and its fretting wear mechanism undergoes a transformation. Specifically, at 20,000 cycles, surface plastic deformation primarily causes material damage. While at 40,000 cycles, an oxide plastic deformation layer appears on the material surface, where adhesive wear and oxidation wear become the primary wear mechanisms. When N increases to 80,000, plastic strain accumulates continually on the material surface, causing the oxide plastic deformation layer in the outer contact area to break and detach gradually. Adhesive wear transforms into abrasive wear, cracks occur inside the material, and fatigue wear becomes a significant wear mechanism. This study fills the research gap in the fretting wear evolution mechanism of 60Si2MnA steel. [ABSTRACT FROM AUTHOR]

The fretting wear behaviors of silicone rubber under dry friction and different lubrication conditions are studied experimentally. Water, engine oil, dimethyl silicone oil (DSO), and dimethyl silicone oil doped with graphene oxide (DSO/GO) are selected as lubricants. Under the liquid lubrication conditions, the silicone rubber samples are always immersed in the same volume of lubricant. The contact model of a 440C steel ball and silicone rubber sample is the sphere-on-flat contact. The reciprocating fretting wear experiments are carried out using the reciprocating friction wear tester. A scanning electron microscope and three-dimensional white-light interference profilometer are used to detect the surface wear morphology and obtain the wear volume, respectively. The influences of normal force, lubrication condition, and displacement amplitude on fretting wear behavior are discussed. The fretting wear performances of silicone rubber under different fretting states and lubrication conditions are compared. The results show that for a small normal force, silicone rubber has the best wear resistance under DSO/GO lubrication. While for a large normal force, silicone rubber has the best wear resistance under engine oil lubrication. [ABSTRACT FROM AUTHOR]

A systematic experimental investigation concerning the fretting-induced tribo-chemical state and its effect on the fretting wear behavior of titanium alloys under the vacuum atmospheres (4 × 10–3 Pa and 4 × 10–1 Pa) in different fretting regimes is reported. An in situ XPS analysis tester was developed to capture the real tribo-chemical state of worn surface for all test conditions. Results show that samples subjected to different vacuum atmospheres have varied tribo-chemical states depending on the fretting regime, which play significantly different roles in determining the associated damage mechanisms and the resulting fretting wear resistance. Under both vacuum atmospheres, in the partial slip regime (PSR) the worn scars were mainly covered by TiO2, showing comparable levels of very slight damage, while in the mixed fretting regime (MFR), the tribo-layer is still mainly consisted of TiO2, but with an evident peak of Ti metal for the high vacuum degree (4 × 10–3 Pa) in MFR, showing a mild damage. In contrast, in the gross slip regime (GSR), Ti metal was prone to be oxidized to Ti2O3 and TiO on the worn scar, especially for the low vacuum degree (4 × 10–1 Pa) having a highest content of Ti2O3. It might be inferred that the tribo-layer containing more Ti2O3 formed during fretting wear process is susceptible to be broken, hence showing a highest fretting wear volume in GSR for the low vacuum degree. The results suggest that for the vacuum environments, the Ti6Al4V may be more suitable to be used under the high vacuum atmosphere. [ABSTRACT FROM AUTHOR]

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To widen the industrial application of additively manufactured (AM) parts, the study of fretting wear behavior is essential, as it ensures the safety and reliability that drive innovation in design and materials. This study explores the fretting wear behavior of the as-built and heat-treated state of AlSi10Mg alloy fabricated, viz., laser powder bed fusion (LPBF). Initially, the as-built and T5, T6, and stress-relieved (SR) heat-treated samples were examined using scanning electron microscopy (SEM) to gain insights into the microstructural changes. The as-built samples exhibited a higher hardness level (135 HV) primarily due to the presence of very fine microstructure of the α-Al cellular matrix with embedded Si. The α-Al cellular structure dissolved with various heat treatments, and Si particles coarsened. The hardness decreased to 85, 79, and 67 HV for the T5, T6, and SR conditions, respectively. Subsequently, fretting tests were conducted on the samples, applying various normal loads of 10, 50, and 100 N. Further, the samples were characterized by the coefficient of friction (COF), worn surface morphology, and wear volume loss. The investigation showed that the as-built material showed less wear volume loss under all loading conditions than the heat-treated conditions. Furthermore, the T5 heat treated sample had a lower wear volume when compared to the T6 and SR heat-treated samples. The heat-treated sample exhibits compressive stress, whereas the LPBF processed, the as-built sample shows tensile stress.

Fretting wear is one of the main degradation mechanisms produced in steel wire and it is widely used for the lifting and handling of equipments. The main objective of the present work is to analyse the mechanical properties of the fretting and non-fretting wire. Statics tensile tests were performed on non-fretting wire and pre-damaged artificially fretting wire subsequently, after that tensile stress (σT), tensile strain (εT), and breaking load (BL) were measured for both wires and their basic mechanical properties were compared. For the analysis wire diameter values varies from 7 mm to 9 mm and artificially pre-damaged wire having reduced diameters varies from 5.8 mm to 8.1 mm were used. From these tests the basic mechanical properties values of maximum tensile stress, tensile strain, modulus of elasticity (E), breaking load (BL) 1610 N/mm², 12.08%, 78854.3 Mpa and 56.73 KN respectively were obtained, for pre-damaged artificially fretting wire. On the other hand, for the non-fretting wire, the values of maximum tensile stress, tensile strain, modulus of elasticity, and breaking load have been obtained as 1171.5 MPa, 16.40 %, 63289.4 MPa and 58.7 KN respectively. [ABSTRACT FROM AUTHOR]

In order to systematically study the effect of different modulation periods on the friction and wear behavior of nickel-based single-crystal superalloy materials during micromotion wear, molecular dynamics methods were used to establish models of nickel-based single-crystal alloys with different modulation periods. The atomic displacement, wear marks, surface morphology, temperature, stress, dislocations, and dislocation density during the friction process were studied. The study found that as the modulation period decreases, the atomic displacements on the surface and subsurface of the workpiece increase, the wear track depth decreases, the debris is more prone to accumulate on both sides of the abrasive ball, the surface roughness of the wear track region increases. In contrast, the surface roughness of the unworked region decreases. The temperature of the workpiece increases, and the stress values of the system become higher. Moreover, the number of defects and dislocation density in the subsurface of the workpiece are higher. This article has important significance and reference value for determining the suitable working environment and accurately predicting the life of nickel-based single crystal superalloy materials. [ABSTRACT FROM AUTHOR]

The fretting wear behavior of fluorine rubber (FKM) and short carbon fiber (SCF) reinforced fluorine rubber matrix composites (SCF/FKMCs) is investigated experimentally under air condition. Four kinds of SCF/FKMCs with different SCF concentrations (5 phr, 10 phr, 15 phr, and 20 phr in every 100 phr of FKM) are considered. The contact model utilizes the sphere-on-flat contact between a 440 C stainless steel ball and an FKM or SCF/FKMCs coating perfectly bonded to a ceramic sheet in fretting experiments. The impacts of SCF concentration, normal force, and displacement amplitude on the fretting wear behavior are investigated. Scanning electron microscope (SEM) is used to analyze the fretting wear surface morphology and wear mechanism, while three-dimensional (3D) white-light interference profilometer is used to describe the characteristics of 3D surface wear profile and determine the wear volume. The fretting wear performances of FKM and SCF/FKMCs with different SCF concentrations are compared under different fretting test conditions. The results show that adding an appropriate amount of SCFs to FKM can improve wear resistance and reduce the coefficient of friction (COF). SCF/FKMC with SCF concentration of 15 phr has the smallest COF. SCF/FKMCs with SCF concentration of 5 phr or 15 phr have the best wear resistance for small normal force or large displacement amplitude. [ABSTRACT FROM AUTHOR]

The formation of tribolayers may play significant influences on fretting wear. At elevated temperature, the adhesion among wear debris and the increased diffusion rate facilitate the formation of tribolayers. However, the intensification of oxidation at elevated temperature and the low diffusion rate in oxides may play an adverse role. The present study aims to investigate the role of temperature in tribolayers in fretting wear using a γ-TiAl alloy. Scanning electron microscope, energy dispersive spectrometer, Raman spectrometer, transmission electron microscope and nanoindentation were utilized to investigate the wear debris, tribolayers, and wear scars. The fretting tests showed that, compared with that at room temperature (RT) and 350 °C, significant reduction in wear rate and decrease in the fluctuation of friction coefficient occurred at 550 and 750 °C. It was further revealed that when temperature raised from room temperature (RT) to 750 °C, the oxidation of the wear debris increased slightly and the diffusion coefficients increased prominently, which facilities the formation of well tribo-sintered tribolayers. The well tribo-sintered tribolayers presented homogenous structure, nanocrystalline grains with excellent mechanical properties, and resulted in the improvement in the fretting wear resistance of the γ-TiAl alloy at 550 and 750 °C. [ABSTRACT FROM AUTHOR]

Fretting damage on contacting surfaces introduces major challenges in mechanical assemblies. Thermal sprayed hardmetal coatings are extensively used for surface modification in tribological applications under demanding conditions and may also be subjected to fretting-inducing loading. In the present work, the fretting behavior of High Velocity Oxy-Fuel (HVOF) and High Velocity Air–Fuel (HVAF) sprayed WC-10Co-4Cr coatings against quenched and tempered (QT) steel was studied by using a single bolt joint-type fretting experiment. This experimental approach was selected to obtain realistic data on the fretting fatigue performance of the contact pairs (both coating-to-steel and coating-to-coating). Experimental results were completed with continuum-scale linear elastic finite element method (FEM) calculations. [ABSTRACT FROM AUTHOR]

A method is proposed for protecting frictional pairs from fretting wear at high temperatures, without lubricant. In fretting wear of steel frictional pairs, the temperature has the main influence on the wear resistance. A system is developed for fretting wear tests with heating. This system is used to determine the wear resistance of steel samples in a frictional pair on fretting with heating to 200°C. [ABSTRACT FROM AUTHOR]

Press-in connections are the commonly used methods for connecting machinery components. In relation to that wide use, those connections are liable to various types of damage and wear. Therefore, this article proposes one of the methods which may improve the life of the press-in connection. CrN+OX, TiN, and ZrN coatings made in the PVD technology were used. The coatings were applied on shafts mating with sleeves and subjected to a rotational bending moment. Tests and observations were conducted that enabled the assessment of the influence of those coatings on the development of wear, in particular fretting, in the tribological kinematic pair. The tests showed the development of wear on all the observed shaft surfaces, with a lower intensity of damage recorded on coated shafts compared to uncoated ones. The traces of fretting wear were noted each time at the edges of the connection, which is due to the mechanism of wear development under rotational bending conditions. In the case of uncoated shafts, wear occurs at the entire circumference of the axle seat in the form of a 3–4 mm wide ring; however, that width is different on either side. In the case of coated shafts, wear occurs on the circumference of the axle seat in the form of a thin ring 1–3 mm wide, depending on the coating. In the case of a ZrN coating, fretting wear appears locally. The largest surface area occupied by wear is 0.75 cm2. Fretting wear comprises mainly material build-ups, pits, and surface scratches. In addition to fretting wear, damage resulting from the process of forcing the sleeve onto the shaft was observed on the tested surfaces. [ABSTRACT FROM AUTHOR]

The tribological properties of γ-TiAl alloys under sliding condition have been well established, but the mechanisms for fretting wear, especially at elevated temperature, remain to be further clarified. In the present study, the tribological behaviors and mechanisms of a γ-TiAl alloy were investigated under an elevated temperature fretting condition. The wear scars, debris, and tribolayers were studied with scanning electron microscope, energy dispersive spectrometer, and Raman spectrometer. The structural and mechanical properties of the tribolayers were investigated utilizing transmission electron microscope and nanoindentation tests. The results demonstrated that the severe adhesive wear, delamination, and abrasive wear in the early stage of fretting resulted in high wear rate of the γ-TiAl alloy. As fretting progresses, the formation of tribolayers with nanograins and excellent mechanical properties improved the fretting wear resistance of the γ-TiAl alloy. Due to the protective effect of the adhesively transferred γ-TiAl, the wear rate of the nickel-based superalloy counterpart was significantly lower. [ABSTRACT FROM AUTHOR]

Abstract The formation of tribolayers may play significant influences on fretting wear. At elevated temperature, the adhesion among wear debris and the increased diffusion rate facilitate the formation of tribolayers. However, the intensification of oxidation at elevated temperature and the low diffusion rate in oxides may play an adverse role. The present study aims to investigate the role of temperature in tribolayers in fretting wear using a γ-TiAl alloy. Scanning electron microscope, energy dispersive spectrometer, Raman spectrometer, transmission electron microscope and nanoindentation were utilized to investigate the wear debris, tribolayers, and wear scars. The fretting tests showed that, compared with that at room temperature (RT) and 350 °C, significant reduction in wear rate and decrease in the fluctuation of friction coefficient occurred at 550 and 750 °C. It was further revealed that when temperature raised from room temperature (RT) to 750 °C, the oxidation of the wear debris increased slightly and the diffusion coefficients increased prominently, which facilities the formation of well tribo-sintered tribolayers. The well tribo-sintered tribolayers presented homogenous structure, nanocrystalline grains with excellent mechanical properties, and resulted in the improvement in the fretting wear resistance of the γ-TiAl alloy at 550 and 750 °C.

Fretting wear is a phenomenon occurring in many engineering objects, including push fit connections. In view of a large number of factors conducive to wear development, it is difficult to describe the mechanism of wear initiation and development. Therefore, various methods are sought to limit wear development. The use of a lubricant may be one of those ways. The aim of this article is to present the results of testing the influence of a lubricant medium on the development of fretting wear in interference fit connections. As a lubricant medium, MoS2 and Whitmore greases were used. For that purpose, wear tests were first conducted on the shaft/sleeve tribological kinematic pair, and then observations and laboratory measurements were performed. The observations demonstrated the presence of fretting wear traces on all tested samples, irrespective of the tribological kinematic pair being tested. The main kind of damage consisted of material build-ups which, during operation, become oxidised and, while moving along the connection, caused local abrasion and micropits. The best results in restricting the development of fretting wear were achieved with Whitmore grease.

Fretting wear of the stay cable is an important factor affecting the service life of the cable. To accurately calculate the extent of fretting wear, it is necessary to calculate the internal contact pressure in the cable. Although there are many theories and experiments on the contact behavior between wires, there are still no theoretical formulations for calculating the distribution of contact pressure in stay cables. In this paper, by studying the transfer effect of contact pressure in the cable, the PIC (parallel wire cable internal point contact pressure) model for calculating the contact pressure in the parallel wire cable is proposed, considering the effects of wire twisting, sheath compression, and cable bending on the contact pressure. A finite element model corresponding to the contact mode between steel wires is established, and the effectiveness of the PIC model is verified through numerical simulation analysis and a comparison of the existing contact models. The results indicate that contact pressure caused by wire twisting (CWT) is superimposed layer by layer inwards, with the contact pressure increasing closer to the inner layers, and its magnitude is mainly related to the axial tension and twist angle. Simultaneously, on the same layer, contact points along the diagonal experience the greatest contact pressure. Contact pressure caused by sheath compression (CSC) is assumed to conform to the Boussinesq distribution, with the outer layers exhibiting greater contact pressure compared to the inner layers. Contact pressure caused by cable bending (CCB) conforms to the two-dimensional closely arranged contact force transmission model, has a clear layering phenomenon, and the contact pressure within the same layer does not change significantly. The magnitude of the contact pressure is exponentially related to the curvature of the cable and proportional to the tension of the cable, which explains the reason why the slip occurs later for the cables with high tensile forces. Among these three types of contact pressure, CWT is the greatest, followed by CCB, while CSC is the smallest. The theoretical analysis results show that factors such as wire radius, tension, torsion angle, and wire position have an impact on contact pressure. Contact pressure is transmitted along force chains within the cable, following the superposition law between layers. It is uncertain whether slip occurs in the neutral axis or in the outermost layer because of the different distributions of tangential force and interlayer frictional resistance between the layers of wires. Fretting wear simulations of two wires demonstrate that contact pressure has a significant influence on wear patterns, and the "averaging" of contact pressure is a major reason for achieving uniform interface wear. While the contact width increases proportionally with the contact pressure, excessive contact pressure can complicate the problem by changing the contact mode from gross slip to partial slip. This study provides a theoretical method for calculating contact pressures at any contact point within the cables in engineering practice. [ABSTRACT FROM AUTHOR]

Compacted graphite cast iron is widely used in the field of diesel engines, and the fretting wear phenomenon of the joint surface will produce fatigue cracks, wear pits, etc., which will affect the life and reliability of the engine. The objective of this study is to investigate the effect of normal load and displacement amplitude on the fretting wear behaviors of compacted graphite cast iron. First, fretting wear behaviors of compacted graphite cast iron are revealed through the running condition fretting map. Under the condition of low normal load and large displacement amplitude, the gross slip region dominates, and the damage mechanism is mainly abrasive wear and plastic deformation. Under the condition of high normal load and small displacement amplitude, the partial slip region dominates, mainly adhesive wear, accompanied by oxidation wear and fatigue wear. Second, the study shows that the friction coefficient after stabilization decreases with the decrease of displacement amplitude and the increase of normal load, and the minimum value is 0.061. Third, the surface profile of wear scar and the wear rate is measured and calculated. Increasing the normal load can effectively reduce the wear rate to 1.88 × 10−3 mm3/N mm. Studying the fretting wear behaviors of compacted graphite cast iron has important theoretical significance for engine fatigue prevention. [ABSTRACT FROM AUTHOR]

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Fretting wear phenomena arise when the tube collides with an intermediate support plate (ISP) under flow-induced vibrations and these vibrations can cause severe damage to the heat exchanger tubes. So, it is important to perform wear scar analysis of tubes to understand wear trends that lead to failure. This experimental study deals with scar analysis using a low-speed closed-loop water tunnel for an aluminium tube with a diameter of 12.7 mm. Three different ISP were used alternatively in the centre of the tube bundle. The tubes in the bundle are arranged parallelly in a triangular configuration with a Pitch-to-Diameter (P/D) ratio of 1.45. The experiments have been performed for each support plate thickness against six different time durations with an increment of half an hour and a cross-flow velocity of 0.5 m/s. The triaxial wireless accelerometer was used to measure the vibration response. The analysis revealed that the ISP tends to wear the circumferential length of the tube surface when they interacted for maximum time. When the thickness of the ISP increases, the film thickness between the tube and the baffle hole increases; resulting in a low amplitude of vibration because of the increased damping effect. Wear work rate and wear volume rate analysis indicated that the ISP of smaller thickness caused an earlier tube failure. [ABSTRACT FROM AUTHOR]

AISI 316L stainless steel has received considerable attention as a common material for key ball valve components; however, its properties cannot be improved through traditional phase transformation, and fretting wears the contact interface between valve parts. A carburized layer was prepared on the surface of AISI 316L stainless steel by using double-glow low-temperature plasma carburization technology. This study reveals the effect of double-glow low-temperature plasma carburization technology on the fretting wear mechanism of AISI 316L steel under different normal loads and displacements. The fretting wear behavior and energy dissipation of the AISI 316L steel and the carburized layer were studied on an SRV-V fretting friction and wear machine with ball–plane contact. The wear mark morphology was analyzed by using scanning electron microscopy (SEM), the phase structure of the carburized layer was characterized with X-ray diffractometry (XRD), and the wear profile and wear volume were evaluated with laser confocal microscopy. The carburized layer contains a single Sc phase, a uniform and dense structure, and a metallurgically combined matrix. After plasma carburizing, the sample exhibited a maximum surface hardness of 897 ± 18 HV0.2, which is approximately four times higher than that of the matrix (273 ± 33 HV0.2). Moreover, the surface roughness was approximately doubled. The wear depth, wear rate, and frictional dissipation energy coefficient of the carburized layer were significantly reduced by up to approximately an order of magnitude compared with the matrix, while the wear resistance and fretting wear stability of the carburized layer were significantly improved. Under different load conditions, the wear mechanism of the AISI 316L steel changed from adhesive wear and abrasive wear to adhesive wear, fatigue delamination, and abrasive wear. Meanwhile, the wear mechanism of the carburized layer changed from adhesive wear to adhesive wear and fatigue delamination, accompanied by a furrowing effect. Under variable displacement conditions, both the AISI 316L steel and carburized layer mainly exhibited adhesive wear and fatigue peeling. Oxygen elements accumulated in the wear marks of the AISI 316L steel and carburized layer, indicating oxidative wear. The fretting wear properties of the AISI 316L steel and carburized layer were determined using the coupled competition between mechanical factors and thermochemical factors. Low-temperature plasma carburization technology improved the stability of the fretting wear process and changed the fretting regime of the AISI 316L steel and could be considered as anti-wearing coatings of ball valves. [ABSTRACT FROM AUTHOR]

In this paper, the friction durability of an anodized aluminum alloy is investigated on relation to the effects of two elaboration parameters: the anodizing time (called the reaction time RT) and the applied current (J). For this purpose, the tribological behavior of the developed oxide layer is characterized using scratch and reciprocating cyclic friction tests under dry and severe conditions. Energy-dispersive x-ray spectroscopy, scanning electron microscopy and surface profilometry were used to correlate between the cyclic response and the worn surfaces and to highlight the impact of RT and J. The anodized layer exhibited an excellent wear resistance at 90 min RT, but its friction durability decreased at 30 min RT. The morphology of the anodized surface influenced the establishment and evolution of the friction-wear layer, which acted as a glass layer for 30 min RT/1A/dm2 (J) and an abrasive third body resource for 90 min RT/1A/dm2 (J) and for 30 min RT/2A/dm2 (J). The variation in the thickness, which affected by the change of the J and RT, has a strong influence on the adhesion strength of the oxide layer. The higher the oxide layer thickness is, the greater the adhesion strength. [ABSTRACT FROM AUTHOR]

A microwave hybrid heating technique has been employed to develop NiCr-Mo-SiC composite cladding on titanium alloy (Grade-5/Ti-6Al-4 V/Titan-31). The developed claddings have been characterized for microstructural features, phase analysis, microhardness measurements, and 3D optical profile parameters by employing scanning electron microscopy, x-ray diffraction, Vickers microhardness tester, and 3D optical profilometer, respectively. Microwave clads have been subjected to linear reciprocator ball on plate wear test with static alumina indenter. Wear track parameters and friction coefficients have been studied. A dense microstructure with uniform distribution of hard phases and good metallurgical bonding with no visible pores and cracks has been obtained. Cladding exhibits nearly 2 times higher hardness than the base alloy. Coefficient of friction studies revealed that higher molybdenum content enhances internal lubricity. [ABSTRACT FROM AUTHOR]

This investigation intends to come up with a cost-efficient and easily available bamboo leaf ash (BLA) which has high content of Silica, as an effective and complimenting reinforcement for the production of magnesium alloy-based metal matrix composites. By incorporating SiC and BLA reinforcement to AZ91D Mg alloy, the composites were made using the bottom pouring stir casting technique. The ratio between SiC and BLA in the composite, respectively, varied as 0:0, 6:0, 0:6, 4:2, 3:3, 2:4 wt.%. Fretting wear is one of the fundamental modes of wear for any mating parts which have vibration with low amplitude. In this study, an integrated Taguchi-TOPSIS is adapted to make the process variables more optimal for fretting wear of composites. Material composition, load, temperature, time, frequency and stroke length are selected as process parameters. The objective is to minimize the coefficient of friction, volume loss and surface roughness. Using the TOPSIS approach, the multi-criteria optimization approach was reduced to a single-criteria issue. The results revealed AZ91D/2 wt.% SiC/4 wt.% BLA, 10N, room temperature, 30-min, 30 Hz and 0.7 mm stroke as optimal parameters. Microscopic study demonstrates that fretting wear occurs in the partial slip zone for the composite tested at optimal condition. With temperature, the wear regime in composites shifts from partial slip to mixed fretting, whereas in alloys, the wear regime shifts from mixed fretting to gross slip. When the correct set of circumstances are available, hybrid composite can function well as a replacement for traditional materials in machineries vulnerable to fretting wear. [ABSTRACT FROM AUTHOR]

Thermomechanical action during high-performance diamond grinding of sintered cutting Al2O3/TiC and SiAlON ceramics leads to increased defectiveness of the surface layer of the deposited TiZrN and CrAlSiN/DLC coatings. It predetermines the discontinuous and porous coatings and reduces its effectiveness under abrasive exposure and fretting wear. The developed technological approach is based on "dry" etching with beams of accelerated argon atoms with an energy of 5 keV for high-performance removal of defects. It ensures the removal of the defective layer on ceramics and reduces the index of defectiveness (the product of defects' density per unit surface area) by several orders of magnitude, compared with diamond grinding. There are no pronounced discontinuities and pores in the microstructure of coatings. Under mechanical loads, the coatings ensure a stable boundary anti-friction film between the ceramics and counter body that significantly increases the wear resistance of samples. The treatment reduces the volumetric wear under 20 min of abrasive action by 2 and 6 times for TiZrN and CrAlSiN/DLC coatings for Al2O3/TiC and by 5 and 23 times for SiAlON. The volumetric wear under fretting wear at 105 friction cycles is reduced by 2–3 times for both coatings for Al2O3/TiC and by 3–4 times for SiAlON. [ABSTRACT FROM AUTHOR]

The fretting wear and adhesive wear resistance of Al and Fe-based thin solid films deposited onto MDN121 steel are studied. Plasma-assisted cathodic arc evaporation technique (P-CAE) is used to develop AlCN/AlC and FeCrN monolayer coatings. The coatings and wear tracks are characterised by FESEM-EDS, nanoindentation, Raman spectroscopy, optical profiler, and confocal microscope. The results reveal that during fretting and adhesive wear, tracks are investigated using confocal microscopy and electron microscopy. When fretting wear occurs, the Coefficient of Friction (COF) dramatically decreases for AlCN/AlC thin solid films by 48.65% and for FeCrN thin solid films by 62.16% when compared to the substrate. FeCrN coating exhibits lower volumetric wear loss than AlCN/AlC coating. The wear surface morphology of both monolayer coverings against galling failure in the substrate exposes the abrasive form of the fretting wear process. Thin solid films of AlCN/AlC and FeCrN experience a COF reduction during adhesive wear of 40.89% and 56.22%, respectively, in comparison to the substrate. The FeCrN monolayer coating exhibits low friction and wear rate compared to AlCN/AlC monolayer coating. [ABSTRACT FROM AUTHOR]

Impact-sliding caused by random vibrations between tubes and supports can affect the operation of heat exchangers. In addition, a corrosive environment can cause damage, accelerating the synergism of corrosion and wear. Therefore, the focus of this work was the impact-sliding fretting tribocorrosion behavior of 316L heat exchanger tubes at different halide concentrations. A device system incorporating the in situ electrochemical measurements of impact-sliding fretting corrosion wear was constructed, and experiments on 316L heat exchanger tubes in sodium chloride (NaCl) solution with different concentrations (0.0, 0.1, 0.5, 1.0, 3.5, and 5.0 wt%) were carried out. The synergism between wear and corrosion was also calculated and analyzed. The wear and damage mechanisms were elucidated by correlating the corrosion-wear synergism, morphologies, and material loss rates. The results indicated that the stable wear stage occurred at approximately 9–12 h, after which the corrosion current increased with the expansion of the wear area. As the halide concentration increased, the scale of damage on the wear scars gradually decreased, changing from being dominated by cracks, delaminations, and grooves to being dominated by scratches, microgrooves, and holes. There was an obvious positive synergism between wear and corrosion. The material loss was dominated by pure mechanical wear and wear enhanced by corrosion, but corrosion enhanced by wear contributed more than tangential sliding fretting corrosion. The total mass loss increased gradually in the range of 0.0–0.5 wt% and decreased in the range of 0.5–5.0 wt%. Large-scale damage enhanced by corrosivity and small-scale damage reduced by lubricity dominated the material loss at low and high concentrations, respectively. [ABSTRACT FROM AUTHOR]