A dual motion combined by radial and tangential fretting was achieved on a modified hydraulic fretting wear test rig. The dual motion fretting tests of medical pure titanium （TA2） and Ti6Al7Nb alloy in artificial sa...A dual motion combined by radial and tangential fretting was achieved on a modified hydraulic fretting wear test rig. The dual motion fretting tests of medical pure titanium （TA2） and Ti6Al7Nb alloy in artificial saliva were carried out under varied contact inclined angles （45° and 60°）, and the maximum imposed load varied from 200 to 400 N at a constant loading speed of 6 mm/min. The effects of the cyclic vertical force and the inclined angle were investigated in detail. Dynamic analysis in combination with microscopic examinations shows that the wear scar and plastic deformation accumulation present a strong asymmetry. The Ti6Al7Nb has better wear resistance than TA2 in artificial saliva at the same test parameters, and with the increase of inclined angle and decrease of imposed load, the wear reduces accordingly. The wear mechanisms of pure titanium TA2 and Ti6Al7Nb alloy under the condition of dual motion fretting in artificial saliva are abrasive wear, oxidative wear and delamination.展开更多
The effects of nanosecond laser shock peening without coating(LSPwC)and nanosecond stacked femtosecond laser shock peening compound strengthening(LSP-CS)on the surface integrity and fretting fatigue lifetime at 500℃o...The effects of nanosecond laser shock peening without coating(LSPwC)and nanosecond stacked femtosecond laser shock peening compound strengthening(LSP-CS)on the surface integrity and fretting fatigue lifetime at 500℃of GH 4169 dovetail component were investigated.The results show that LSP treatment does not significantly lead to changes in the grain size of GH 4169 alloy,but it introduces a large number of dislocations,resulting in the formation of a plastic deformation layer and residual compressive stress layer.The surface microhardness increased by 20.5%and 28.6%after being treated by LSPwC and LSP-CS,respectively.The surface residual compressive stresses were(-306.5±42.5)MPa and(-404.3±34.7)MPa,respectively;The depth of both the hardening layer and the residual compressive stress layer is 400μm,and along the cross-section with 0-100μm region after LSP-CS treatment has higher hardness and greater residual compressive stress.The fretting fatigue lifetime of the GH 4169 dovetail component at 500℃was increased by 346.8%and 494.9%,which is the result of the combined effects of the hardening layer and the residual stress layer.The LSP-CS treatment can effectively make up for the disadvantage of the LSPwC treatment,and further enhance the fretting fatigue lifetime of the GH 4169 dovetail component at high temperature.展开更多
Submerged Abrasive Waterjet Peening(SAWJP)shows great application potential in augmenting the fatigue properties of metallic parts.Thus,the present work aims to investigate the influence of SAWJP on the Surface Integr...Submerged Abrasive Waterjet Peening(SAWJP)shows great application potential in augmenting the fatigue properties of metallic parts.Thus,the present work aims to investigate the influence of SAWJP on the Surface Integrity(SI)and Fretting Fatigue(FF)properties of Inconel 718(IN718)superalloy and illustrate the microstructural evolution,FF life improvement,and fretting wear mechanism.First,the SI of the IN718 specimen was examined following treatment via SAWJP.Results showed that the specimen subjected to SAWJP formed a total plastic deformation layer of 56μm.The maximum microhardness and Compressive Residual Stress(CRS)measured across the depth of the SAWJP-treated specimens exhibited an increase in values ranging between 522 HV and 541 HV and 1171–1380 MPa,respectively.The FF test results of the specimen before and after SAWJP treatment at ambient temperatures indicated that the FF life of the SAWJP-treated specimen surpassed that of the as-received specimen by a factor of 2.81.The examination of the FF fracture,contact surface,and crack propagation behavior revealed the crucial factors contributing to the enhanced FF resistance of the IN718 specimen,including the gradient nanostructure characterized by ultra-refined grains,substantial CRS,and elevated microhardness,which were all induced by the SAWJP treatment.展开更多
CrN coatings are also employed to protect structural materials in nuclear power plants.It should be noted that the preparation process utilizing physical vapor deposition(PVD)techniques inevitably entails certain defe...CrN coatings are also employed to protect structural materials in nuclear power plants.It should be noted that the preparation process utilizing physical vapor deposition(PVD)techniques inevitably entails certain defects.Such a phenomenon will affect the protective properties of CrN coatings.In this study,low-energy laser shock peening(LE-LSP)with varying energies was employed for the post-treatment of CrN coatings.The effects of different laser energy LE-LSP treatments on the surface morphology,crystal structure and fretting wear properties of CrN coatings were investigated.The results revealed that the surface of the CrN coatings subjected to LE-LSP underwent significant plastic deformation and displayed a regular texture structure.The surface roughness and Vickers hardness of the CrN coatings exhibit a significant increase.Under a laser energy of 150 mJ,the surface hardness exhibits a maximum increase of 2.35 times.The residual stress of CrN coatings diminishes with the augmentation of laser energy due to the formation of surface cracks.Following LE-LSP treatment,the columnar crystal structure of the CrN coating was disrupted and fragmented into fine grains due to the impact force.As the laser energy augments,the fragmented CrN grains undergo further compaction.During fretting wear,all specimens were in the gross slip regime.The wear mechanism of the CrN coating,120 and 150 mJ specimens are primarily dominated by abrasive wear,and accompanied by oxidative wear.For specimens treated with 30,60 and 90 mJ,the predominant wear mechanisms are mainly peeling and abrasive wear,and accompanied by oxidative wear.Both the wear area and wear volume initially increase and then decrease as the laser energy increases.The 150 mJ specimen exhibited the smallest wear area and wear volume of all tested specimens.The wear volume was reduced by 76.32%when compared to that of the CrN coating.This study complements the existing research on PVD/LSP composite strengthening techniques.Introduces a novel post-treatment methodology for PVD coatings.Provides certain theoretical support for subsequent PVD/LSP composite strengthening.展开更多
The torsional fretting wear tests of 7075 aluminum alloy flat against 52100 steel ball in dry condition were carried out on a new high-precision torsional fretting-wear tester.The kinetics behaviors and damage mechani...The torsional fretting wear tests of 7075 aluminum alloy flat against 52100 steel ball in dry condition were carried out on a new high-precision torsional fretting-wear tester.The kinetics behaviors and damage mechanism of 7075 aluminum alloy under different angular displacement amplitudes were investigated in detail.The results show that the torsional fretting running behaviors of 7075 aluminum alloy can be defined by three fretting regimes(i.e.partial slip regime(PSR),mixed fretting regime(MFR) and slip regime(SR)) with the increase of angular displacement amplitudes.In PSR,the damage occurs at the lateral portion of the contact zone with a slight annular shape.However,in MFR and SR,more severe damages are observed and the debris layer covers the wear scars.Friction torque and dissipation energy which are strongly dependent upon the imposed angular displacement amplitudes and presented in three stages were discussed in detail.The mechanisms of torsional fretting wear of aluminum alloy are mainly oxidative wear,abrasive wear and delamination in the three fretting regimes.In addition,the oxidative debris plays an important role during the torsional fretting wear processes.展开更多
Given that fretting wear causes failure in steel wires, we carried out tangential fretting wear tests of steel wires on a self-made fretting wear test rig under contact loads of 9 and 29 N and fretting amplitudes rang...Given that fretting wear causes failure in steel wires, we carried out tangential fretting wear tests of steel wires on a self-made fretting wear test rig under contact loads of 9 and 29 N and fretting amplitudes ranging from 5 to 180 μm. We observed morphologies of fretted steel wire surfaces on an S-3000N scanning electron microscope in order to analyze fretting wear mecha-nisms. The results show that the fretting regime of steel wires transforms from partial slip regime into mixed fretting regime and gross slip regime with an increase in fretting amplitudes under a given contact load. In partial slip regime, the friction coefficient has a relatively low value. Four stages can be defined in mixed fretting and gross slip regimes. The fretting wear of steel wires in-creases obviously with increases in fretting amplitudes. Fretting scars present a typical morphology of annularity, showing slight damage in partial slip regime. However, wear clearly increases in mixed fretting regime where wear mechanism is a combination of plastic deformation, abrasive wear and oxidative wear. In gross slip regime, more severe degradation is present than in the other regimes. The main fretting wear mechanisms of steel wires are abrasive wear, surface fatigue and friction oxidation.展开更多
The fretting wear behavior of 0Cr20Ni32AlTi alloy was investigated with crossed cylinder contact under 80 N at 300 and 400 °C.Wear scar and debris were analyzed systematically by scanning electron microscopy and ...The fretting wear behavior of 0Cr20Ni32AlTi alloy was investigated with crossed cylinder contact under 80 N at 300 and 400 °C.Wear scar and debris were analyzed systematically by scanning electron microscopy and X-ray photoelectron spectroscopy.The results show that the friction logs are mixed fretting regime and gross slip regime with the magnitudes of displacement of 10 and 20 μm,respectively.Severe wear and friction oxidation occur on the material surface.A large number of granular debris produced in the fretting process can be easily congregated and adhered at the contact zone after repeated crushes.The resultant of friction oxidation is mainly composed of Fe3O4,Fe2O3,Cr2O3 and NiO.Temperature and friction are the major factors affecting the oxidation reaction rate.The fretting friction effect can enhance the oxidation reaction activity of surface atoms of 0Cr20Ni32AlTi alloy and reduce the oxidation activation energy.As result,the oxidation reaction rate is accelerated.展开更多
Various doses of nitrogen ions were implanted into the surface of pure titanium, Ti6Al7Nb and Ti6Al4V, by plasma immersion ion implantation. Torsional fretting wear tests involving flat specimens of no-treated and tre...Various doses of nitrogen ions were implanted into the surface of pure titanium, Ti6Al7Nb and Ti6Al4V, by plasma immersion ion implantation. Torsional fretting wear tests involving flat specimens of no-treated and treated titanium, as well as its alloys, against a ZrO2 ball contact were performed on a torsional fretting wear test rig using a simulated physiological medium of serum solution. The treated surfaces were characterized, and the effect of implantation dose on torsional fretting behavior was discussed in detail. The results showed that the torsional fretting running and damage behavior of titanium and its alloys were strongly dependent on the dose of the implanted nitrogen ions and the angular displacement amplitude. The torsional fretting running boundary moved to smaller angular displacement amplitude, and the central light damage zone decreased, as the ion dose increased. The wear mechanisms of titanium and its alloys were oxidative wear, abrasive wear and delamination, with abrasive wear as the most common mechanism of the ion implantation layers.展开更多
The friction and wear behaviors of Inconel 690 flat against Si3Ni4 ball were investigated using a hydraulic fretting test rig equipped with a liquid container device. The loads of 20-80 N, reciprocating amplitudes of ...The friction and wear behaviors of Inconel 690 flat against Si3Ni4 ball were investigated using a hydraulic fretting test rig equipped with a liquid container device. The loads of 20-80 N, reciprocating amplitudes of 80-200 μm and two different environments （distilled water and hydrazine solution at temperatures from 25 to 90 ℃） were selected. The results show that the ratio of Ft/Fn is lower in distilled water than that in hydrazine solution at the same temperature in the slip regime. Both the ratio of Ft/Fn and wear volume gradually increase with increasing medium temperature under the given normal load and displacement amplitude. Besides the displacement amplitude and load, temperature also plays an important role for wear behavior of Inconel 690 material. The increase of temperature could reduce the concentration of dissolved oxygen, and promote the absorption reaction of hydrazine and dissolved oxygen. As a result, the oxidative corrosion rate is obviously lowered. Abrasive wear and delamination wear are the main mechanisms of Inconel 690 in distilled water. However, in hydrazine solution the cracks accompanied by abrasive wear and delamination wear are the main mechanisms.展开更多
This study investigated the fretting wear and fatigue of full-scale railway axles.Fatigue tests were conducted on full-scale railway axles,and the fretting wear and fretting fatigue in the fretted zone of the railway ...This study investigated the fretting wear and fatigue of full-scale railway axles.Fatigue tests were conducted on full-scale railway axles,and the fretting wear and fretting fatigue in the fretted zone of the railway axles were analysed.Three-dimensional finite element models were established based on the experimental results.Then,multi-axial fatigue parameters and a linear elastic fracture mechanics-based approach were used to investigate the fretting fatigue crack initiation and propagation,respectively,in which the role of the fretting wear was taken into account.The experimental and simulated results showed that the fretted zone could be divided into zones I-III according to the surface damage morphologies.Fretting wear alleviated the stress concentration near the wheel seat edge and resulted in a new stress concentration near the worn/unworn boundary in zone II,which greatly promoted the fretting crack initiation at the inner side of the fretted zone.Meanwhile,the stress concentration also increased the equivalent stress intensity factor range DKeq below the mating surface,and thus promoted the propagation of fretting fatigue crack.Based on these findings,the effect of the stress redistribution resulting from fretting wear is suggested to be taken into account when evaluating the fretting fatigue in railway axles.展开更多
The introduction of surface engineering is expected to be an effective strategy against fretting damage.A large number of studies show that the low gas multi-component(such as carbon,nitrogen,sulphur and oxygen,etc)th...The introduction of surface engineering is expected to be an effective strategy against fretting damage.A large number of studies show that the low gas multi-component(such as carbon,nitrogen,sulphur and oxygen,etc)thermo-chemical treatment(LTGMTT)can overcome the brittleness of nitriding process,and upgrade the surface hardness and improve the wear resistance and fatigue properties of the work-pieces significantly.However,there are few reports on the anti-fretting properties of the LTGMTT modified layer up to now,which limits the applications of fretting.So this paper discusses the fretting wear behavior of modified layer on the surface of LZ50(0.48%C)steel prepared by low temperature gas multi-component thermo-chemical treatment(LTGMTT)technology.The fretting wear tests of the modified layer flat specimens and its substrate(LZ50 steel)against 52100 steel balls with diameter of 40 mm are carried out under normal load of 150 N and displacement amplitudes varied from 2μm to 40μm.Characterization of the modified layer and dynamic analyses in combination with microscopic examinations were performed through the means of scanning electron microscope(SEM),optical microscope(OM),X-ray diffraction(XRD)and surface profilometer.The experimental results showed that the modified layer with a total thickness of 60μm was consisted of three parts,i.e.,loose layer,compound layer and diffusion layer.Compared with the substrate,the range of the mixed fretting regime(MFR)of the LTGMTT modified layer diminished,and the slip regime(SR)of the modified layer shifted to the direction of smaller displacement amplitude.The coefficient of friction(COF)of the modified layer was lower than that of the substrate in the initial stage.For the modified layer,the damage in partial slip regime(PSR)was very slight.The fretting wear mechanism of the modified layer both in MFR and SR was abrasive wear and delamination.The modified layer presented better wear resistance than the substrate in PSR and MFR;however,in SR,the wear resistance of the modified layer decreased with the increase of the displacement amplitudes.The experimental results can provide some experimental bases for promoting industrial application of LTGMTT modified layer in anti-fretting wear.展开更多
The fretting wear behavior of Zr alloy cladding tube under mixed fretting regime in a high-temperature pressurized water was investigated.The main wear mechanism is adhesive wear,with characters of small-scale delamin...The fretting wear behavior of Zr alloy cladding tube under mixed fretting regime in a high-temperature pressurized water was investigated.The main wear mechanism is adhesive wear,with characters of small-scale delamination at the center of worn area and serious delamination on the worn edge.A long crack throughout the worn area and other cracks propagated towards the substrate are observed.The cross-sectional microstructure of worn area can be divided into a thick third-body layer,thin inner oxide layer and thick tribologically transformed structure layer,and their formation mechanisms are analyzed in detail.Finally,the mixed fretting regime process and the microstructural evolution during fretting wear are discussed.展开更多
Taking the typical face gear connection structure of the combined rotor as the research object,this paper studies the distribution rules of the contact state,contact stress and slip distance of the contact tooth surfa...Taking the typical face gear connection structure of the combined rotor as the research object,this paper studies the distribution rules of the contact state,contact stress and slip distance of the contact tooth surface of face gear under different centrifugal force and temperature conditions by using the finite element method,in order to improve the reliability of face gear connection structure.And the influence of centrifugal force and temperature on the maximum wear depth of the tooth surface is studied based on the fretting wear model proposed by McColl.Results show that:(1)The external diameter has an opening phenomenon on the contact surface of the face gear under the centrifugal effect,which reduces the load-bearing area;(2)The contact stress at the inner root of the face gear is the largest and the wear is the most serious;(3)The temperature field causes the contact surface to be thermally expanded,resulting in the large uneven deformation,and the tooth surface appears drum-shape;(4)The maximum contact stress and the maximum wear depth occur in the middle of the tooth root;(5)As the temperature increases,the maximum wear depth of the tooth surface increases significantly.Consequently,reducing temperature of the combined rotor plays an important role in effectively reducing the wear of the face gear and improving the connection life of face gear connection structure.展开更多
Fretting oxidization is a main form of fretting chemical damage. In this paper, a theory analysis was proceeded for several key factors affecting this damage and one kind of fretting map based on the co-effect of thos...Fretting oxidization is a main form of fretting chemical damage. In this paper, a theory analysis was proceeded for several key factors affecting this damage and one kind of fretting map based on the co-effect of those key factors were presented. By the map, not only the mode of fretting oxide can be learned better, but also it is possible to reduce fretting damage through changing working and material parameters reasonably.展开更多
An extensive study of the composition distribution, bonding strength, hardness, and wear resistance of a 0Cr18Ni9 film deposited on a Ti811 titanium alloy surface by ion beam enhanced deposition （IBED） is presented....An extensive study of the composition distribution, bonding strength, hardness, and wear resistance of a 0Cr18Ni9 film deposited on a Ti811 titanium alloy surface by ion beam enhanced deposition （IBED） is presented. Shot peening was introduced to post-treat the modified surface to synergistically improve the fretting fatigue resistance of the Ti811 alloy at 350°C. The results indicate that the 0Cr18Ni9 film with high density, small grain size, low void radio, and high bonding strength can be prepared using IBED. As a result, the hardness, wear resistance, and fretting fatigue resistance of the Ti811 alloy are increased to a remarkable extent. Compared with shot peening treatment or IBED 0Cr18Ni9 film alone, the Ti811 titanium alloy with an IBED 0Cr18Ni9 film combined with shot peening shows a higher fretting fatigue resistance at 350°C. This is due to the synergistic effect of the high wear resistance of the film surface and the residual compressive stress induced by shot peening.展开更多
The impact fretting wear has largely occurred at nuclear power device induced by the flow-induced vibra- tion, and it will take potential hazards to the service of the equipment. However, the present study focuses on ...The impact fretting wear has largely occurred at nuclear power device induced by the flow-induced vibra- tion, and it will take potential hazards to the service of the equipment. However, the present study focuses on the tangential fretting wear of alloy 690 tubes. Research on impact fretting wear of alloy 690 tubes is limited and the related research is imminent. Therefore, impact fretting wear behavior of alloy 690 tubes against 304 stainless steels is investigated. Deionized water is used to simulate the flow environment of the equipment, and the dry envi- ronment is used for comparison. Varied analytical tech- niques are employed to characterize the wear and tribochemical behavior during impact fretting wear. Char- acterization results indicate that cracks occur at high impact load in both water and dry equipment; however, the water as a medium can significantly delay the cracking time. The crack propagation behavior shows a jagged shape in the water, but crack extended disorderly in dry equip- ment because the water changed the stress distribution and retarded the friction heat during the wear process. The SEM and XPS analysis shows that the main failure mechanisms of the tube under impact fretting are fatiguewear and friction oxidation. The effect of medium（water） on fretting wear is revealed, which plays a potential and promising role in the service of nuclear power device and other flow equipments.展开更多
Micro-arc oxidation(MAO)coating was prepared on Ti6Al4V alloy surface and its characterizations were detected by Vickers hardness tester,profilometer,scanning electric microscope(SEM),energy dispersive X-ray spectrome...Micro-arc oxidation(MAO)coating was prepared on Ti6Al4V alloy surface and its characterizations were detected by Vickers hardness tester,profilometer,scanning electric microscope(SEM),energy dispersive X-ray spectrometer(EDX)and X-ray diffractometer(XRD).Fretting wear behaviors of the coating and its substrate were comparatively tested without lubrication under varied displacement amplitudes(D)in a range of 3-40μm,constant normal load(Fn)of 300 N and frequency of 5 Hz.The results showed that the MAO coating,presenting rough and porous surface and high hardness,mainly consisted of rutile and anatase TiO2 phases.Compared with the substrate,the MAO coating could shift the mixed fretting regime(MFR)and slip regime(SR)to a direction of smaller displacement amplitude.In the partial slip regime(PSR),lower friction coefficients and slight damage appeared due to the coordination of elastic deformation of contact zones.In the MFR,the friction coefficient of the coating was lower than that of the substrate as a result of the prevention of plastic deformation by the hard ceramic surface.With the increase of the displacement amplitude,the degradation of the MAO coating and the substrate increased extremely.The fretting wear mechanisms of the coating were abrasive wear and delamination with some material transfer of specimen.In addition,the coating presented a better property for alleviating fretting wear.展开更多
At present,there are many studies on the residual stress field and plastic strain field introduced by surface strengthening,which can well hinder the initiation of early fatigue cracks and delay the propagation of fat...At present,there are many studies on the residual stress field and plastic strain field introduced by surface strengthening,which can well hinder the initiation of early fatigue cracks and delay the propagation of fatigue cracks.However,there are few studies on the effects of these key factors on fretting wear.In the paper,shot-peening(SP)and ultrasonic surface rolling process(USRP)were performed on Ti-6Al-4V plate specimens.The surface hardness and residual stresses of the material were tested by vickers indenter and X-ray diffraction residual stress analyzer.Microhardness were measured by HXD-1000MC/CD micro Vickers hardness tester.The effects of different surface strengthening on its fretting fatigue properties were verified by fretting fatigue experiments.The fretting fatigue fracture surface and wear morphology of the specimens were studied and analyzed by means of microscopic observation,and the mechanism of improving fretting fatigue life by surface strengthening process was further explained.After USRP treatment,the surface roughness of Ti-6Al-4V is significantly improved.In addition,the microhardness of the specimen after SP reaches the maximum at 80μm from the surface,which is about 123%higher than that of the AsR specimen.After USRP,it reaches the maximum at 150μm from the surface,which is about 128%higher than that of AsR specimen.It is also found that the residual compressive stress of the specimens treated by USRP and SP increases first and then decreases with the depth direction,and the residual stress reaches the maximum on the sub surface.The USRP specimen reaches the maximum value at 0.18 mm,about−550 MPa,while the SP specimen reaches the maximum value at 0.1 mm,about−380 MPa.The fretting fatigue life of Ti-6Al-4V effectively improved after USRP and SP.The surface integrity of specimens after USRP is the best,which has deeper residual compressive stress layer and more refined grain.In this paper,a fretting wear device is designed to carry out fretting fatigue experiments on specimens with different surface strengthening.展开更多
The tribology behaviors of Ti6Al7Nb,its alloy with N-ion implantation,and its alloy with diamond-like carbon(DLC)coating were investigated in artificial saliva.Fretting wear tests of untreated,N-ion implanted and DLC ...The tribology behaviors of Ti6Al7Nb,its alloy with N-ion implantation,and its alloy with diamond-like carbon(DLC)coating were investigated in artificial saliva.Fretting wear tests of untreated,N-ion implanted and DLC coated Ti6Al7Nb alloys plate against a Si3N4ball were carried out on a reciprocating sliding fretting wear test rig.Based on the analysis of X-ray diffraction,Raman spectroscopy,3-D profiler,SEM morphologies and frictional kinetics behavior analysis,the damage behavior of surface modification layer was discussed in detail.The results indicated that the fretting wear behavior of Ti6Al7Nb alloy with N-ion implantation was increased with the dose increase of the implanted nitrogen ions.Moreover,the DLC-coated Ti6Al7Nb alloy with low ion implantation could improve the fretting wear behavior greatly.In addition,the Ti6Al7Nb with DLC coating had better ncorrosion resistance due to the special compact structure.All results suggested that the Ti6Al7Nb with DLC coating had better wear resistance than that with N-ion implantation in artificial saliva.展开更多
A new continuum damage mechanics model for fretting fatigue life prediction is established. In this model, the damage evolution rate is described by two kinds of quantities. One is associated with the cyclic stress ch...A new continuum damage mechanics model for fretting fatigue life prediction is established. In this model, the damage evolution rate is described by two kinds of quantities. One is associated with the cyclic stress characteristics obtained by the finite element （FE） analysis, and the other is associated with the material fatigue property identified from the fatigue test data of standard specimens. The wear is modeled by the energy wear law to simulate the contact geometry evolution. A two-dimensional （2D） plane strain FE implementation of the damage mechanics model and the energy wear model is presented in the platform of ABAQUS to simulate the evolutions of the fatigue damage and the wear scar. The effect of the specimen thickness is also investigated. The predicted results of the crack initiation site and the fretting fatigue life agree well with available experimental data. Comparisons are made with the critical plane Smith- Watson-Topper （SWT） method.展开更多
基金Project(81170996)supported by the National Natural Science Foundation of China
文摘A dual motion combined by radial and tangential fretting was achieved on a modified hydraulic fretting wear test rig. The dual motion fretting tests of medical pure titanium （TA2） and Ti6Al7Nb alloy in artificial saliva were carried out under varied contact inclined angles （45° and 60°）, and the maximum imposed load varied from 200 to 400 N at a constant loading speed of 6 mm/min. The effects of the cyclic vertical force and the inclined angle were investigated in detail. Dynamic analysis in combination with microscopic examinations shows that the wear scar and plastic deformation accumulation present a strong asymmetry. The Ti6Al7Nb has better wear resistance than TA2 in artificial saliva at the same test parameters, and with the increase of inclined angle and decrease of imposed load, the wear reduces accordingly. The wear mechanisms of pure titanium TA2 and Ti6Al7Nb alloy under the condition of dual motion fretting in artificial saliva are abrasive wear, oxidative wear and delamination.
基金Project(2022YFB3401900)supported by the the National Key R&D of ChinaProject(2025YFHZ0163)supported by the the Science and Technology Projects in Sichuan Province,ChinaProject(2682024GF004)supported by Fundamental Research Funds for the Centeral University,China。
文摘The effects of nanosecond laser shock peening without coating(LSPwC)and nanosecond stacked femtosecond laser shock peening compound strengthening(LSP-CS)on the surface integrity and fretting fatigue lifetime at 500℃of GH 4169 dovetail component were investigated.The results show that LSP treatment does not significantly lead to changes in the grain size of GH 4169 alloy,but it introduces a large number of dislocations,resulting in the formation of a plastic deformation layer and residual compressive stress layer.The surface microhardness increased by 20.5%and 28.6%after being treated by LSPwC and LSP-CS,respectively.The surface residual compressive stresses were(-306.5±42.5)MPa and(-404.3±34.7)MPa,respectively;The depth of both the hardening layer and the residual compressive stress layer is 400μm,and along the cross-section with 0-100μm region after LSP-CS treatment has higher hardness and greater residual compressive stress.The fretting fatigue lifetime of the GH 4169 dovetail component at 500℃was increased by 346.8%and 494.9%,which is the result of the combined effects of the hardening layer and the residual stress layer.The LSP-CS treatment can effectively make up for the disadvantage of the LSPwC treatment,and further enhance the fretting fatigue lifetime of the GH 4169 dovetail component at high temperature.
基金financially supported by the National Key Research and Development Project,China(Nos.2018YFA0703300,2022YFB4600019)the National Natural Science Foundation of China(Nos.52275148,52405154)+2 种基金the Innovation Program Phase II of AECC Commercial Aircraft Engine Co.Ltd,China(No.HT-3RJC1053-2020)support by the Postdoctoral Fellowship Program of CPSF,China(No.GZB20240219)the Shanghai Sailing Program,China(No.24YF2708100).
文摘Submerged Abrasive Waterjet Peening(SAWJP)shows great application potential in augmenting the fatigue properties of metallic parts.Thus,the present work aims to investigate the influence of SAWJP on the Surface Integrity(SI)and Fretting Fatigue(FF)properties of Inconel 718(IN718)superalloy and illustrate the microstructural evolution,FF life improvement,and fretting wear mechanism.First,the SI of the IN718 specimen was examined following treatment via SAWJP.Results showed that the specimen subjected to SAWJP formed a total plastic deformation layer of 56μm.The maximum microhardness and Compressive Residual Stress(CRS)measured across the depth of the SAWJP-treated specimens exhibited an increase in values ranging between 522 HV and 541 HV and 1171–1380 MPa,respectively.The FF test results of the specimen before and after SAWJP treatment at ambient temperatures indicated that the FF life of the SAWJP-treated specimen surpassed that of the as-received specimen by a factor of 2.81.The examination of the FF fracture,contact surface,and crack propagation behavior revealed the crucial factors contributing to the enhanced FF resistance of the IN718 specimen,including the gradient nanostructure characterized by ultra-refined grains,substantial CRS,and elevated microhardness,which were all induced by the SAWJP treatment.
基金Supported by National Key R&D Projects(Grant No.2022YFB3401900)Sichuan Provincial Science and Technology Projects(Grant No.2022JDJQ0019)Fundamental Research Funds for the Central University(Grant No.2682024GF004).
文摘CrN coatings are also employed to protect structural materials in nuclear power plants.It should be noted that the preparation process utilizing physical vapor deposition(PVD)techniques inevitably entails certain defects.Such a phenomenon will affect the protective properties of CrN coatings.In this study,low-energy laser shock peening(LE-LSP)with varying energies was employed for the post-treatment of CrN coatings.The effects of different laser energy LE-LSP treatments on the surface morphology,crystal structure and fretting wear properties of CrN coatings were investigated.The results revealed that the surface of the CrN coatings subjected to LE-LSP underwent significant plastic deformation and displayed a regular texture structure.The surface roughness and Vickers hardness of the CrN coatings exhibit a significant increase.Under a laser energy of 150 mJ,the surface hardness exhibits a maximum increase of 2.35 times.The residual stress of CrN coatings diminishes with the augmentation of laser energy due to the formation of surface cracks.Following LE-LSP treatment,the columnar crystal structure of the CrN coating was disrupted and fragmented into fine grains due to the impact force.As the laser energy augments,the fragmented CrN grains undergo further compaction.During fretting wear,all specimens were in the gross slip regime.The wear mechanism of the CrN coating,120 and 150 mJ specimens are primarily dominated by abrasive wear,and accompanied by oxidative wear.For specimens treated with 30,60 and 90 mJ,the predominant wear mechanisms are mainly peeling and abrasive wear,and accompanied by oxidative wear.Both the wear area and wear volume initially increase and then decrease as the laser energy increases.The 150 mJ specimen exhibited the smallest wear area and wear volume of all tested specimens.The wear volume was reduced by 76.32%when compared to that of the CrN coating.This study complements the existing research on PVD/LSP composite strengthening techniques.Introduces a novel post-treatment methodology for PVD coatings.Provides certain theoretical support for subsequent PVD/LSP composite strengthening.
基金Project(2007CB714704) supported by the National Basic Research Program of ChinaProjects(50775192,50821063) supported by the National Natural Science Foundation of China
文摘The torsional fretting wear tests of 7075 aluminum alloy flat against 52100 steel ball in dry condition were carried out on a new high-precision torsional fretting-wear tester.The kinetics behaviors and damage mechanism of 7075 aluminum alloy under different angular displacement amplitudes were investigated in detail.The results show that the torsional fretting running behaviors of 7075 aluminum alloy can be defined by three fretting regimes(i.e.partial slip regime(PSR),mixed fretting regime(MFR) and slip regime(SR)) with the increase of angular displacement amplitudes.In PSR,the damage occurs at the lateral portion of the contact zone with a slight annular shape.However,in MFR and SR,more severe damages are observed and the debris layer covers the wear scars.Friction torque and dissipation energy which are strongly dependent upon the imposed angular displacement amplitudes and presented in three stages were discussed in detail.The mechanisms of torsional fretting wear of aluminum alloy are mainly oxidative wear,abrasive wear and delamination in the three fretting regimes.In addition,the oxidative debris plays an important role during the torsional fretting wear processes.
基金supported by the National Natural Science Foundation of China (No 50875252)the Program for New Century Excellent Talents in Universities (NoNCET-06-0479)the Natural Science Foundation of Jiangsu Province (NoBK2008005)
文摘Given that fretting wear causes failure in steel wires, we carried out tangential fretting wear tests of steel wires on a self-made fretting wear test rig under contact loads of 9 and 29 N and fretting amplitudes ranging from 5 to 180 μm. We observed morphologies of fretted steel wire surfaces on an S-3000N scanning electron microscope in order to analyze fretting wear mecha-nisms. The results show that the fretting regime of steel wires transforms from partial slip regime into mixed fretting regime and gross slip regime with an increase in fretting amplitudes under a given contact load. In partial slip regime, the friction coefficient has a relatively low value. Four stages can be defined in mixed fretting and gross slip regimes. The fretting wear of steel wires in-creases obviously with increases in fretting amplitudes. Fretting scars present a typical morphology of annularity, showing slight damage in partial slip regime. However, wear clearly increases in mixed fretting regime where wear mechanism is a combination of plastic deformation, abrasive wear and oxidative wear. In gross slip regime, more severe degradation is present than in the other regimes. The main fretting wear mechanisms of steel wires are abrasive wear, surface fatigue and friction oxidation.
基金Project (51075342) supported by the National Natural Science Foundation of ChinaProject (2007CB714704) supported by the National Basic Research Program of China
文摘The fretting wear behavior of 0Cr20Ni32AlTi alloy was investigated with crossed cylinder contact under 80 N at 300 and 400 °C.Wear scar and debris were analyzed systematically by scanning electron microscopy and X-ray photoelectron spectroscopy.The results show that the friction logs are mixed fretting regime and gross slip regime with the magnitudes of displacement of 10 and 20 μm,respectively.Severe wear and friction oxidation occur on the material surface.A large number of granular debris produced in the fretting process can be easily congregated and adhered at the contact zone after repeated crushes.The resultant of friction oxidation is mainly composed of Fe3O4,Fe2O3,Cr2O3 and NiO.Temperature and friction are the major factors affecting the oxidation reaction rate.The fretting friction effect can enhance the oxidation reaction activity of surface atoms of 0Cr20Ni32AlTi alloy and reduce the oxidation activation energy.As result,the oxidation reaction rate is accelerated.
基金Projects(U1530136,51375407)supported by the National Natural Science Foundation of China
文摘Various doses of nitrogen ions were implanted into the surface of pure titanium, Ti6Al7Nb and Ti6Al4V, by plasma immersion ion implantation. Torsional fretting wear tests involving flat specimens of no-treated and treated titanium, as well as its alloys, against a ZrO2 ball contact were performed on a torsional fretting wear test rig using a simulated physiological medium of serum solution. The treated surfaces were characterized, and the effect of implantation dose on torsional fretting behavior was discussed in detail. The results showed that the torsional fretting running and damage behavior of titanium and its alloys were strongly dependent on the dose of the implanted nitrogen ions and the angular displacement amplitude. The torsional fretting running boundary moved to smaller angular displacement amplitude, and the central light damage zone decreased, as the ion dose increased. The wear mechanisms of titanium and its alloys were oxidative wear, abrasive wear and delamination, with abrasive wear as the most common mechanism of the ion implantation layers.
基金Project(51075342)supported by the National Natural Science Foundation of China
文摘The friction and wear behaviors of Inconel 690 flat against Si3Ni4 ball were investigated using a hydraulic fretting test rig equipped with a liquid container device. The loads of 20-80 N, reciprocating amplitudes of 80-200 μm and two different environments （distilled water and hydrazine solution at temperatures from 25 to 90 ℃） were selected. The results show that the ratio of Ft/Fn is lower in distilled water than that in hydrazine solution at the same temperature in the slip regime. Both the ratio of Ft/Fn and wear volume gradually increase with increasing medium temperature under the given normal load and displacement amplitude. Besides the displacement amplitude and load, temperature also plays an important role for wear behavior of Inconel 690 material. The increase of temperature could reduce the concentration of dissolved oxygen, and promote the absorption reaction of hydrazine and dissolved oxygen. As a result, the oxidative corrosion rate is obviously lowered. Abrasive wear and delamination wear are the main mechanisms of Inconel 690 in distilled water. However, in hydrazine solution the cracks accompanied by abrasive wear and delamination wear are the main mechanisms.
基金the Independent Research Project of the State Key Laboratory of Traction Power(No.2018TPL_Z01)the National Natural Science Foundation of China(No.51375406)the Fundamental Research Funds for the Central Universities(No.2682018CX68).
文摘This study investigated the fretting wear and fatigue of full-scale railway axles.Fatigue tests were conducted on full-scale railway axles,and the fretting wear and fretting fatigue in the fretted zone of the railway axles were analysed.Three-dimensional finite element models were established based on the experimental results.Then,multi-axial fatigue parameters and a linear elastic fracture mechanics-based approach were used to investigate the fretting fatigue crack initiation and propagation,respectively,in which the role of the fretting wear was taken into account.The experimental and simulated results showed that the fretted zone could be divided into zones I-III according to the surface damage morphologies.Fretting wear alleviated the stress concentration near the wheel seat edge and resulted in a new stress concentration near the worn/unworn boundary in zone II,which greatly promoted the fretting crack initiation at the inner side of the fretted zone.Meanwhile,the stress concentration also increased the equivalent stress intensity factor range DKeq below the mating surface,and thus promoted the propagation of fretting fatigue crack.Based on these findings,the effect of the stress redistribution resulting from fretting wear is suggested to be taken into account when evaluating the fretting fatigue in railway axles.
基金supported by National Natural Science Foundation of China(Grant No.50521503)National Basic Research Program of China(973 Program,Grant No.2007CB714704)National Hi-tech Research and Development Program of China(863 Program,Grant No.2006AA04Z406)
文摘The introduction of surface engineering is expected to be an effective strategy against fretting damage.A large number of studies show that the low gas multi-component(such as carbon,nitrogen,sulphur and oxygen,etc)thermo-chemical treatment(LTGMTT)can overcome the brittleness of nitriding process,and upgrade the surface hardness and improve the wear resistance and fatigue properties of the work-pieces significantly.However,there are few reports on the anti-fretting properties of the LTGMTT modified layer up to now,which limits the applications of fretting.So this paper discusses the fretting wear behavior of modified layer on the surface of LZ50(0.48%C)steel prepared by low temperature gas multi-component thermo-chemical treatment(LTGMTT)technology.The fretting wear tests of the modified layer flat specimens and its substrate(LZ50 steel)against 52100 steel balls with diameter of 40 mm are carried out under normal load of 150 N and displacement amplitudes varied from 2μm to 40μm.Characterization of the modified layer and dynamic analyses in combination with microscopic examinations were performed through the means of scanning electron microscope(SEM),optical microscope(OM),X-ray diffraction(XRD)and surface profilometer.The experimental results showed that the modified layer with a total thickness of 60μm was consisted of three parts,i.e.,loose layer,compound layer and diffusion layer.Compared with the substrate,the range of the mixed fretting regime(MFR)of the LTGMTT modified layer diminished,and the slip regime(SR)of the modified layer shifted to the direction of smaller displacement amplitude.The coefficient of friction(COF)of the modified layer was lower than that of the substrate in the initial stage.For the modified layer,the damage in partial slip regime(PSR)was very slight.The fretting wear mechanism of the modified layer both in MFR and SR was abrasive wear and delamination.The modified layer presented better wear resistance than the substrate in PSR and MFR;however,in SR,the wear resistance of the modified layer decreased with the increase of the displacement amplitudes.The experimental results can provide some experimental bases for promoting industrial application of LTGMTT modified layer in anti-fretting wear.
基金financially supported by the CNNC Science Fund for Talented Young Scholars,the Youth Innovation Promotion As-sessment CAS(No.2022187)the National Natural Science Founda-tion of China(No.52105221)+1 种基金the IMR Innovation Fund(No.2021-PY10)the open-ended fund of the CAS Key Laboratory of Nu-clear Materials and Safety Assessment(Institute of Metal Research,Chinese Academy of Sciences,China)(No.2020NMSAKF01).
文摘The fretting wear behavior of Zr alloy cladding tube under mixed fretting regime in a high-temperature pressurized water was investigated.The main wear mechanism is adhesive wear,with characters of small-scale delamination at the center of worn area and serious delamination on the worn edge.A long crack throughout the worn area and other cracks propagated towards the substrate are observed.The cross-sectional microstructure of worn area can be divided into a thick third-body layer,thin inner oxide layer and thick tribologically transformed structure layer,and their formation mechanisms are analyzed in detail.Finally,the mixed fretting regime process and the microstructural evolution during fretting wear are discussed.
基金supported by the National Natural Science of China(No.11872288)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2019JM-219)。
文摘Taking the typical face gear connection structure of the combined rotor as the research object,this paper studies the distribution rules of the contact state,contact stress and slip distance of the contact tooth surface of face gear under different centrifugal force and temperature conditions by using the finite element method,in order to improve the reliability of face gear connection structure.And the influence of centrifugal force and temperature on the maximum wear depth of the tooth surface is studied based on the fretting wear model proposed by McColl.Results show that:(1)The external diameter has an opening phenomenon on the contact surface of the face gear under the centrifugal effect,which reduces the load-bearing area;(2)The contact stress at the inner root of the face gear is the largest and the wear is the most serious;(3)The temperature field causes the contact surface to be thermally expanded,resulting in the large uneven deformation,and the tooth surface appears drum-shape;(4)The maximum contact stress and the maximum wear depth occur in the middle of the tooth root;(5)As the temperature increases,the maximum wear depth of the tooth surface increases significantly.Consequently,reducing temperature of the combined rotor plays an important role in effectively reducing the wear of the face gear and improving the connection life of face gear connection structure.
文摘Fretting oxidization is a main form of fretting chemical damage. In this paper, a theory analysis was proceeded for several key factors affecting this damage and one kind of fretting map based on the co-effect of those key factors were presented. By the map, not only the mode of fretting oxide can be learned better, but also it is possible to reduce fretting damage through changing working and material parameters reasonably.
基金supported by the National Natural Science Foundation of China (Nos. 50771070 and 50671085)the National High Technical Research and Development program of China (No. 2007AA03Z521)
文摘An extensive study of the composition distribution, bonding strength, hardness, and wear resistance of a 0Cr18Ni9 film deposited on a Ti811 titanium alloy surface by ion beam enhanced deposition （IBED） is presented. Shot peening was introduced to post-treat the modified surface to synergistically improve the fretting fatigue resistance of the Ti811 alloy at 350°C. The results indicate that the 0Cr18Ni9 film with high density, small grain size, low void radio, and high bonding strength can be prepared using IBED. As a result, the hardness, wear resistance, and fretting fatigue resistance of the Ti811 alloy are increased to a remarkable extent. Compared with shot peening treatment or IBED 0Cr18Ni9 film alone, the Ti811 titanium alloy with an IBED 0Cr18Ni9 film combined with shot peening shows a higher fretting fatigue resistance at 350°C. This is due to the synergistic effect of the high wear resistance of the film surface and the residual compressive stress induced by shot peening.
基金Supported by National Natural Science Foundation of China(Grant Nos.51375407,U1530136,51627806)Shanghai Municipal Science and Technology Talent Program of China(Grant No.14R21421500)Young Scientific Innovation Team of Science and Technology of Sichuan(Grant No.2017TD0017)
文摘The impact fretting wear has largely occurred at nuclear power device induced by the flow-induced vibra- tion, and it will take potential hazards to the service of the equipment. However, the present study focuses on the tangential fretting wear of alloy 690 tubes. Research on impact fretting wear of alloy 690 tubes is limited and the related research is imminent. Therefore, impact fretting wear behavior of alloy 690 tubes against 304 stainless steels is investigated. Deionized water is used to simulate the flow environment of the equipment, and the dry envi- ronment is used for comparison. Varied analytical tech- niques are employed to characterize the wear and tribochemical behavior during impact fretting wear. Char- acterization results indicate that cracks occur at high impact load in both water and dry equipment; however, the water as a medium can significantly delay the cracking time. The crack propagation behavior shows a jagged shape in the water, but crack extended disorderly in dry equip- ment because the water changed the stress distribution and retarded the friction heat during the wear process. The SEM and XPS analysis shows that the main failure mechanisms of the tube under impact fretting are fatiguewear and friction oxidation. The effect of medium（water） on fretting wear is revealed, which plays a potential and promising role in the service of nuclear power device and other flow equipments.
基金Project(50521503)supported by the National Natural Science Foundation of ChinaProject(2007CB714704)supported by the National Basic Research Program of ChinaProject(200536)supported by the Foundation of the Author of National Excellent Doctoral Dissertation of China
文摘Micro-arc oxidation(MAO)coating was prepared on Ti6Al4V alloy surface and its characterizations were detected by Vickers hardness tester,profilometer,scanning electric microscope(SEM),energy dispersive X-ray spectrometer(EDX)and X-ray diffractometer(XRD).Fretting wear behaviors of the coating and its substrate were comparatively tested without lubrication under varied displacement amplitudes(D)in a range of 3-40μm,constant normal load(Fn)of 300 N and frequency of 5 Hz.The results showed that the MAO coating,presenting rough and porous surface and high hardness,mainly consisted of rutile and anatase TiO2 phases.Compared with the substrate,the MAO coating could shift the mixed fretting regime(MFR)and slip regime(SR)to a direction of smaller displacement amplitude.In the partial slip regime(PSR),lower friction coefficients and slight damage appeared due to the coordination of elastic deformation of contact zones.In the MFR,the friction coefficient of the coating was lower than that of the substrate as a result of the prevention of plastic deformation by the hard ceramic surface.With the increase of the displacement amplitude,the degradation of the MAO coating and the substrate increased extremely.The fretting wear mechanisms of the coating were abrasive wear and delamination with some material transfer of specimen.In addition,the coating presented a better property for alleviating fretting wear.
基金Supported by National Key Research and Development Project(Grant No.2018YFC1902400)Natural Science Foundation of Shanghai(Grant No.20ZR1415300).
文摘At present,there are many studies on the residual stress field and plastic strain field introduced by surface strengthening,which can well hinder the initiation of early fatigue cracks and delay the propagation of fatigue cracks.However,there are few studies on the effects of these key factors on fretting wear.In the paper,shot-peening(SP)and ultrasonic surface rolling process(USRP)were performed on Ti-6Al-4V plate specimens.The surface hardness and residual stresses of the material were tested by vickers indenter and X-ray diffraction residual stress analyzer.Microhardness were measured by HXD-1000MC/CD micro Vickers hardness tester.The effects of different surface strengthening on its fretting fatigue properties were verified by fretting fatigue experiments.The fretting fatigue fracture surface and wear morphology of the specimens were studied and analyzed by means of microscopic observation,and the mechanism of improving fretting fatigue life by surface strengthening process was further explained.After USRP treatment,the surface roughness of Ti-6Al-4V is significantly improved.In addition,the microhardness of the specimen after SP reaches the maximum at 80μm from the surface,which is about 123%higher than that of the AsR specimen.After USRP,it reaches the maximum at 150μm from the surface,which is about 128%higher than that of AsR specimen.It is also found that the residual compressive stress of the specimens treated by USRP and SP increases first and then decreases with the depth direction,and the residual stress reaches the maximum on the sub surface.The USRP specimen reaches the maximum value at 0.18 mm,about−550 MPa,while the SP specimen reaches the maximum value at 0.1 mm,about−380 MPa.The fretting fatigue life of Ti-6Al-4V effectively improved after USRP and SP.The surface integrity of specimens after USRP is the best,which has deeper residual compressive stress layer and more refined grain.In this paper,a fretting wear device is designed to carry out fretting fatigue experiments on specimens with different surface strengthening.
文摘The tribology behaviors of Ti6Al7Nb,its alloy with N-ion implantation,and its alloy with diamond-like carbon(DLC)coating were investigated in artificial saliva.Fretting wear tests of untreated,N-ion implanted and DLC coated Ti6Al7Nb alloys plate against a Si3N4ball were carried out on a reciprocating sliding fretting wear test rig.Based on the analysis of X-ray diffraction,Raman spectroscopy,3-D profiler,SEM morphologies and frictional kinetics behavior analysis,the damage behavior of surface modification layer was discussed in detail.The results indicated that the fretting wear behavior of Ti6Al7Nb alloy with N-ion implantation was increased with the dose increase of the implanted nitrogen ions.Moreover,the DLC-coated Ti6Al7Nb alloy with low ion implantation could improve the fretting wear behavior greatly.In addition,the Ti6Al7Nb with DLC coating had better ncorrosion resistance due to the special compact structure.All results suggested that the Ti6Al7Nb with DLC coating had better wear resistance than that with N-ion implantation in artificial saliva.
基金supported by the National Natural Science Foundation of China(No.11002010)
文摘A new continuum damage mechanics model for fretting fatigue life prediction is established. In this model, the damage evolution rate is described by two kinds of quantities. One is associated with the cyclic stress characteristics obtained by the finite element （FE） analysis, and the other is associated with the material fatigue property identified from the fatigue test data of standard specimens. The wear is modeled by the energy wear law to simulate the contact geometry evolution. A two-dimensional （2D） plane strain FE implementation of the damage mechanics model and the energy wear model is presented in the platform of ABAQUS to simulate the evolutions of the fatigue damage and the wear scar. The effect of the specimen thickness is also investigated. The predicted results of the crack initiation site and the fretting fatigue life agree well with available experimental data. Comparisons are made with the critical plane Smith- Watson-Topper （SWT） method.
