Zirconium alloy(Zr-4)is extensively utilized in nuclear fuel cladding materials due to its exceptional neutron economy,high ductility,and promising corrosion and irradiation resistance.Nevertheless,during the operatio...Zirconium alloy(Zr-4)is extensively utilized in nuclear fuel cladding materials due to its exceptional neutron economy,high ductility,and promising corrosion and irradiation resistance.Nevertheless,during the operational lifespan of the Zr-4 fuel tube,micro-oscillations induced by the high-speed flow of cooling water can cause wear between the cladding tube and grids.This leads to wear failure of the Zr-4 alloy tube,which seriously threatens the safe operation of nuclear stations.The application of protective coatings onto the surface of zirconium alloys serves to enhance their resistance against wear,while without changing of the existing reactor structure.In this study,FeCrAl/CrN and FeCrAl coatings were fabricated on the surface of Zr-4 alloy using dual-target co-sputtering technology.The effects of the CrN interlayer on the microstructure,mechanical properties,and tribological behavior of FeCrAl coating in air and B-Li water were investigated,and a comparative analysis with Zr-4 alloy was conducted.The results showed that the application of FeCrAl/CrN and FeCrAl coatings significantly enhanced the hardness and wear resistance of Zr-4 alloy.The introduction of the CrN interlayer increased the columnar grain size of the FeCrAl coating and caused a change in the preferred growth direction of the coating from(110)to(211).The CrN interlayer improved the hardness and wear resistance of the coating,it also led to a decrease in adhesion strength.The wear rates of FeCrAl/CrN coatings in air and B-Li water were the lowest,about 3.2×10^(-6) mm^(3)/(N·m)and 6.0×10^(-7) mm^(3)/(N·m),respectively.The lubricating effect of B-Li water effectively reduced the friction coefficient and wear rate of both FeCrAl/CrN and FeCrAl coatings.In air and B-Li water,the primary wear mechanisms for Zr-4 are adhesive wear and oxidative wear,while the main wear mechanisms for FeCrAl/CrN and FeCrAl coatings are abrasive wear and oxidative wear.These findings not only provided a theoretical basis for understanding the microstructure and wear performance of FeCrAl coatings but also offered important technical guidance for their practical application in the nuclear industry.展开更多
Aseries of [(Fe_(0.6)Co_(0.2)Ni_(0.2))_(0.75-0.03x)B_(0.2)Si_(0.05+0.03x)]_(96)Nb_(4) amorphous alloy composite coatings were prepared by adjusting the silicon content(x=0,1,2,3,4,5,and 6)and their microstructures and...Aseries of [(Fe_(0.6)Co_(0.2)Ni_(0.2))_(0.75-0.03x)B_(0.2)Si_(0.05+0.03x)]_(96)Nb_(4) amorphous alloy composite coatings were prepared by adjusting the silicon content(x=0,1,2,3,4,5,and 6)and their microstructures and tribological properties were investigated by laser cladding technique.Additionally,the effect of Si on the glass forming ability(GFA)of the layers was understood.Results show that an appropriate Si content can refine the microstructure of the FeCoNiBSiNb laser cladding layers and improve the mechanical and tribological properties.The hardness of the coating layer increases monotonically with the Si content.At the Si content of 4.8at%(x=0),the coating layer exhibits a relatively low hardness(734.2HV 0.1).Conversely,at the silicon content of 13.44at%(x=3),the coating layer exhibits the highest hardness(1106HV 0.1).The non-crystalline content and tensile strength exhibit an initial increase,followed by a subsequent decrease.At x=2,the coating exhibits its maximum fracture strength(2880 MPa).However,when x>2,the fracture strength of the coating decreases with an increase in x.Conversely,with an increase in Si content,the wear volume loss initially decreases and then increases.At a Si content of 10.56at%(x=2),the coating exhibits the highest non-crystalline content(42%),the highest tensile strength(2880 MPa),and the most favorable dry friction performance.展开更多
The tribological behaviors of Cu-15Ni-8Sn/graphite composites with the graphite content of 38 vol.%against AISI321 stainless steel under dry-sliding,deionized water and sea water were investigated on a block-on-ring c...The tribological behaviors of Cu-15Ni-8Sn/graphite composites with the graphite content of 38 vol.%against AISI321 stainless steel under dry-sliding,deionized water and sea water were investigated on a block-on-ring configuration.The results indicated that the friction coefficient was the lowest under dry-sliding,and the highest in deionized water.The wear rate decreased to reach the minimum value of 1.39×10-15 m^(3)/(N·m)in sea water and in deionized water,it increased to the maximum value of 5.56×10-15 m^(3)/(N·m).The deionized water hindered the formation of tribo-oxide layer and lubricating film,which resulted in the largest friction coefficient and wear rate.In sea water,however,the corrosion products comprised of oxides,hydroxides and chlorides were found on the worn surface,and the compacted layer composed of corrosion products and graphite played an important role in keeping the excellent wear resistance.It was elucidated that the tribological behaviors of Cu-15Ni-8Sn/graphite composite were powerful influenced by the friction environments.展开更多
The cooperative effect of laser surface texturing(LST) and double glow plasma surface alloying on tribological performance of lubricated sliding contacts was investigated.A Nd:YAG laser was used to generate microdimpl...The cooperative effect of laser surface texturing(LST) and double glow plasma surface alloying on tribological performance of lubricated sliding contacts was investigated.A Nd:YAG laser was used to generate microdimples on steel surfaces. Dimples with the diameter of 150μm and the depth of 30-35μm distributed circumferentially on the disc surface.The alloying element Cr was sputtered to the laser texturing steel surface by double glow plasma technique.A deep diffusion layer with a thickness of 30μm and a high hardness of HV900 was formed in this alloy.Tribological experiments of three types of samples(smooth,texturing and texturing+alloying) were conducted with a ring-on-disc tribometer to simulate the face seal.It is found that,in comparison with smooth steel surfaces,the laser texturing samples significantly reduce the friction coefficient.Moreover,the lower wear rate of the sample treated with the two surface techniques is observed.展开更多
A numerical optimization approach based on the finite element(FE) simulation was used to design the optimum irregular gourd-shaped pattern parameters for generating the highest hydrodynamic pressure. Then the optimum ...A numerical optimization approach based on the finite element(FE) simulation was used to design the optimum irregular gourd-shaped pattern parameters for generating the highest hydrodynamic pressure. Then the optimum parameters of the gourd-shaped surface texture were determined and the textures were processed on the stainless steel surface by the laser technology. The tribological performance of gourd-shaped surface texture was analyzed using the type of UMT2 tester, and compared with that of the regular circle surface texture and none-texture surface by considering the effect of sliding speeds and applied loads on the tribological performance. The results show that the compound factor n, the diameter ratio Dr and the texture depth Hd are more significant parameters and the optimum values are 0.618, 2.0 and 4 μm, respectively. In addition, irregular gourd-shaped surface texture with optimum parameters is the most effective in the friction reduction among the patterns investigated under different speeds and applied loads in this work. Moreover, better coordination and combination effect can be obtained by gourd-shaped surface texture. The main reason responsible for the results is the irregular symmetric nature of the gourd-shaped texture along the direction of lubricants flowing which can generate the higher fluid dynamic pressure.展开更多
The effects of hot extrusion and addition of Al_(2)O_(3p) on both microstructure and tribological behavior of 7075 composites were investigated via optical microscopy(OM),scanning electron microscopy(SEM),energy dispe...The effects of hot extrusion and addition of Al_(2)O_(3p) on both microstructure and tribological behavior of 7075 composites were investigated via optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive spectrometry(EDS),and transmission electron microscopy(TEM).The experimental consequences reveal that the optimal addition of Al_(2)O_(3p) was 2 wt%.After hot extrusion,the Mg(Zn,Cu,Al)2 phases partially dissolve into the matrix and generate many uniformly distributed aging precipitation particles,the Al_(7)Cu_(2)Fe phases are squeezed and broken,and the Al_(2)O_(3p) become uniform distribution.The microhardness of as-extruded 2 wt%Al_(2)O_(3p)/7075 composites reaches HV 170.34,increased by 41.5%than as-cast composites.The wear rate of as-extruded 2 wt%Al_(2)O_(3p)/7075 composites is further lower than that of as-cast composites under the same condition.SEM-EDS analyses reveal that the reinforced wear resistance of composites can put down to the protective effect of the Al_(2)O_(3p) reinforced transition layer.After hot extrusion,the transition layer becomes stable,which determines the reinforced wear resistance of the as-extruded composites.展开更多
This work is aimed to study the effect of boron on wear resistance of Fe-Cr-B alloys containing different boron contents(0 wt%,5 wt%,7 wt%and 9 wt%)from room temperature(RT)to 800°C in order to explore their appl...This work is aimed to study the effect of boron on wear resistance of Fe-Cr-B alloys containing different boron contents(0 wt%,5 wt%,7 wt%and 9 wt%)from room temperature(RT)to 800°C in order to explore their applications as high-temperature wear resistant mechanical parts.Additionally,the wear mechanism of alloys is evaluated.The tribological properties of alloys are systematically studied by using a ball-on-disc tribometer at 10 N and 0.20 m/s from RT to 800°C sliding against Si3N4 ceramic ball.The boron element greatly improves the wear resistance of specimens as compared with that of unreinforced specimen.The friction coefficients of specimens decrease with increasing of testing temperature.The wear rates of Fe-Cr-B alloys decrease firstly and then raise with the increase of boron content.The specific wear rates of specimens with boron are 1/10 of the unreinforced specimen.Fe-21wt%Cr-7wt%B keeps the best tribological properties at high temperature.展开更多
Mechanical properties and tribological behavior of a novel cast heat resisting copper based alloy are investigated. The corresponding properties of a commercial aluminum bronze C95500 (ASTM B30) are compared with the ...Mechanical properties and tribological behavior of a novel cast heat resisting copper based alloy are investigated. The corresponding properties of a commercial aluminum bronze C95500 (ASTM B30) are compared with the alloy. The results show that the alloy possesses better mechanical properties and tribological behaviors than that of C95500 at elevated temperature. The tensile strength, elongation and hardness at 500℃ are 470MPa, 2.5% and HB220, respectively. The wear rate of the developed alloy at ambient and elevated temperature is about one sixth and one fortieth of that of C95500, respectively. The alloy is very suitable for ma nufacturing heat resisting and wear resisting parts. Major strengthening mechanisms for the alloy are solution strengthening and the second phase strengthening.展开更多
Ni/n-SiO2 composite coating was electrodeposited by brush-plating with pulse-reverse current（RC）. The morphology, hardness, and tribological properties of the coating were investigated and compared with those of Ni ...Ni/n-SiO2 composite coating was electrodeposited by brush-plating with pulse-reverse current（RC）. The morphology, hardness, and tribological properties of the coating were investigated and compared with those of Ni and composite coatings electrodeposited with direct current（DC）. The results indicate that Ni/n-SiO2 composite coating electrodeposited by RC, because of RC and the nano powders, has denser coating, finer crystal grains, higher hardness（HV650.0, nearly 1.5 times higher than that of Ni coating electrodeposited by DC） and lower friction coefficient（nearly 0.62）, as a result, in the wearing experiment, the Ni/n-SiO2 composite coating electrodeposited by RC has the least worn loss. So this kind of coating has better wear resistance. And RC electro brush-plating can be used as a new technology of brush-plating in the area of wear resistance.展开更多
Nanoparticles are increasingly being used to improve the friction and wear performance of polymers. In this study, we investigated the tribological behavior and energy dissipation characteristics of nano-Al_2O_3-reinf...Nanoparticles are increasingly being used to improve the friction and wear performance of polymers. In this study, we investigated the tribological behavior and energy dissipation characteristics of nano-Al_2O_3-reinforced polytetrafluoroethylenepolyphenylene sulfide(PTFE-PPS) composites in a sliding system. The tribological behaviors of the composites were evaluated under different normal loads(100–300 N) at a high linear velocity(2 m/s) using a block-on-ring tester. Addition of the nano-Al_2O_3 filler improved the antiwear performance of the PTFE-PPS composites, and the friction coefficient increased slightly. The lowest wear rate was obtained when the nano-Al_2O_3 content was 3%(volume fraction). Further, the results indicated a linear correlation between wear and the amount of energy dissipated, even though the wear mechanism changed with the nano-Al_2O_3 content, independent of the normal load applied.展开更多
To improve the solid lubricity on the worn surface of frictional-pairs, a convenient and simple brush-painting technique was utilized to prepare the solid lubrication graphite coatings. The bonding between the coating...To improve the solid lubricity on the worn surface of frictional-pairs, a convenient and simple brush-painting technique was utilized to prepare the solid lubrication graphite coatings. The bonding between the coatings and substrate is good. To examine the influence of the different graphite contents on the tribological properties of the graphite coatings, the comparison experiments were carried out on the ring-on-block friction tester. The tribological results show a change law of saddle-shape between the tribological properties of graphite coatings and graphite content. When the amount of graphite is up to 28g, the tribological properties of graphite coating are the best. The excellent anti-friction of the graphite coating is associated with the close-packed hexagonal crystal structure of graphite.展开更多
Nanostructured n-Al2O3/Ni feedstock for thermal spraying was manufactured by the method of chemical wrapping and spray drying. The nanostructured coating was sprayed with this feedstock. Tribological properties of the...Nanostructured n-Al2O3/Ni feedstock for thermal spraying was manufactured by the method of chemical wrapping and spray drying. The nanostructured coating was sprayed with this feedstock. Tribological properties of the coatings and steel 45# were tested. Within the testing range, the friction coefficient of coatings against GCr15 steel decreased and the mass loss of coatings increased at first then decreased with the increase of load. Under each load, the coatings’ friction coefficients and wear losses were lower than that of steel 45#. Scanning electron microscopy and energy dispersive spectrometer analysis show that adhesion is the dominating wear mechanism, and fatigue exists at the same time. Material transferred from counter-part to the coating is the main factor which influences the coatings’ friction coefficient and wear losses.展开更多
The frictional properties of micro bearings have strong influence on the performance of the whole system because of tiny scale of micro-electromechanical system (MEMS). To develop micro bearings with low friction,it i...The frictional properties of micro bearings have strong influence on the performance of the whole system because of tiny scale of micro-electromechanical system (MEMS). To develop micro bearings with low friction,it is important to evaluate the friction behaviors on the micro bearing. The testing system and the principle to evaluate the tribological performance of micromachining work-pieces under the load of mill Newton scale is introduced in paper "A new approach to measure the friction coefficient of micro journal bearings" of Yao et al,. But as the tribological force is faint in micro scale, the measured force is influenced a lot by the testing error. As the equation of that of Yao’s paper is very sensitive to the measured force, the tested result is influenced remarkably by testing error. So it is hard to get precision result. To solve this problem, the test system with new compensation method is introduced to precisely evaluate tribological performance under mill scale. The new metrology method is developed by means of the error compensation from two sets of testing data. The data are the force collected respectively when the friction counterparts rotate in CW(clockwise) and CCW(counter-clockwise) direction. So we deduce the equation of friction coefficient respctively on the condition of journal running in CCW and CW direction. As condition of measuring those two friciton coefficients are alike except the running direction of journal, and then the friction coefficient should be the same because this difference of direction has no influence on the fricition coefficients. Considering this, we unite the both equation, make the data measured in different subtract each other in the equation, and then a new equation can be gotten. This new equation enhances the metrology precision of friction coefficient theoretically thanks to the counteracting of error values in the equation. Using this method we testing the friction of high speed steel journal with hard alloy bearing. The result shows the new compensation method has better precision and repetition than CW and CCW method thanks to the error resistance.展开更多
Through using mineral oil and synthetic oil to deploy the semisynthesis base oil, modifying the surfaces of ultrafine tungsten disulfide grains by surface chemical embellishment and adsorption embellishment to make th...Through using mineral oil and synthetic oil to deploy the semisynthesis base oil, modifying the surfaces of ultrafine tungsten disulfide grains by surface chemical embellishment and adsorption embellishment to make them suspended steadily in the base oil as solid lubricating additive, and adding some function additives, the tungsten disulfide motor oil was prepared. The tribological characteristics of this kind motor oil and the well-known motor oils in our country and overseas were studied. The results show that the oil film strength of this kind of motor oil is respectively 1.06 and 1.38 times of that of shell helix ultra motor oil and great wall motor oil, and its sintering load is 1.75 and 2.33 times of that of them, and when tested under 392 N, 1 450 r/rain and 30 min, the friction coefficients of friction pairs lubricated by the tungsten disulfide motor oil decrease with the increase of time, meanwhile, the diameter of worn spot is small, and the surface of worn spot is smooth, and no obvious furrows appear. The experiments indicate that the tungsten disulfide motor oil has the better antiwear, antifriction and extreme pressure properties than the well-known motor oils.展开更多
Non lubricated slide performance of functional grade copper matrix composite,fabricated using horizontal centrifuge cast technique was investigated using pin-on-disc tribo-tester.Rate of wear and friction coefficient ...Non lubricated slide performance of functional grade copper matrix composite,fabricated using horizontal centrifuge cast technique was investigated using pin-on-disc tribo-tester.Rate of wear and friction coefficient of the inner wall thickness of hollow cylindrical cast specimen was analyzed using Taguchi based L27 orthogonal array,where the percentage of graphite particles were observed higher.Variable process parameters those influenced the rate of wear directly or indirectly were:applied load(15,25 and 35 N),slide velocity(1.5,2.5 and 3.5 m/s)and slide distance(750,1500 and 2250 m).Rate of wear and friction coefficient showed a proportional dependency with applied load and slide distance,whereas showing a decline during intermediate slide velocity.Signal-to-Noise ratio predicted the minimal tribo-condition,on‘smaller-the-better’basis.Analysis of Variance technique quantified the influence of affecting parameters,along with their interactions.Regression analysis was utilized for the validation of the experimental data.Micrographs and scanning electron microscopy exhibited the wear mechanisms and mechanically mixed layer formation during worn surfaces analysis.展开更多
The aim of present study is to analyze the influence of volume percentage(vol.%) of nano-sized particles(TiB_2: average size is 35 nm) on microstructure, mechanical and tribological behavior of 6061-T6 Al alloy surfac...The aim of present study is to analyze the influence of volume percentage(vol.%) of nano-sized particles(TiB_2: average size is 35 nm) on microstructure, mechanical and tribological behavior of 6061-T6 Al alloy surface nano composite prepared via Friction stir process(FSP). The microstructure of the fabricated surface nanocomposites is examined using optical microscopy(OM) and scanning electron microscope(SEM) for distribution of TiB_2 nano reinforcement particles, thickness of nano composite layer formed on the Aluminum alloy substrate and fracture features. The depth of surface nano composite layer is measured as 3683.82 m m along the cross section of stir zone of nano composite perpendicular to FSP. It was observed that increase in volume percentage of TiB_2 particles, the microhardness is increased up to132 Hv and it is greater than as-received Al alloy's microhardness(104 Hv). It is also observed that at 4volume percentage higher tensile properties exhibited as compared with the 2 and 8 vol. %. It is found that high wear resistance exhibited at 4 volume percentage as-compared with the 2 and 8 vol. %. The observed wear and mechanical properties are interrelated with microstructure, fractography and worn morphology.展开更多
Despite the great achievements made in improvement of wear resistance properties of aluminum alloys, their applications in heavy surface load-bearing are limited. Single coating is insufficient to produce the desired ...Despite the great achievements made in improvement of wear resistance properties of aluminum alloys, their applications in heavy surface load-bearing are limited. Single coating is insufficient to produce the desired combination of surface properties. These problems can be solved through the duplex coatings. The aim of the present study is to overview the research advances on processes of duplex coatings on (aluminum) alloys combined with micro plasma oxidation process and with other modern processes such as physical vapour deposition and plasma assisted chemical vapour deposition and also to evaluate the performance of micro plasma oxidation coatings in improving the load-bearing, friction and wear resistance properties of aluminum alloys in comparison with other coatings. Wherein, a more detailed presentation of the processes and their performances and disadvantages are given as well.展开更多
Oleic acid surface-modified Cu nanoparticles with an average size of 20 nm were prepared by liquid phase reducing reaction. The tribological performance and mechanism of nanocopper as additive were studied by means of...Oleic acid surface-modified Cu nanoparticles with an average size of 20 nm were prepared by liquid phase reducing reaction. The tribological performance and mechanism of nanocopper as additive were studied by means of tribotester, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and nanoindentation instrument. The results indicate that the modified nanocopper additive can significantly improve the wear resistance and reduce friction coefficient of base oil. A copper protective film is formed and contributes to the excellent tribological properties of nanocopper additive. On the basis of the film forming mechanism, a new in-situ repair method was designed and used to repair wear-out-failure injection pump plunger and barrel. Furthermore, the current research progress of nanoparticles as green energy-saving lubricating oil additives were presented.展开更多
Anodic films were successfully fabricated on Ti6A14V alloy by anodic oxidation method in an environmental friendly electrolyte with and without sodium hypochlorite. The anodic films were characterized by means of the ...Anodic films were successfully fabricated on Ti6A14V alloy by anodic oxidation method in an environmental friendly electrolyte with and without sodium hypochlorite. The anodic films were characterized by means of the scanning electron microscope （SEM） and energy dispersive spectrometer （EDS）. Results revealed that the addition of sodium hypochlorite leads to the ultrafast growth of oxide films, and results in the significant changes of morphology and thickness. The influence of sodium hypochlorite on formation and crystallization of oxide films as a function of anodizing time was discussed. Meanwhile, potentiodynamic electrochemical tests and dry sliding wear tests were performed to evaluate the corrosion resistance and tribological properties of oxide films. It was found that the oxide film fabricated with the existence of sodium hypochlorite had improved corrosion resistance and tribological properties than the one formed without sodium hypochlorite. Moreover, the effect mechanism of sodium hypochlorite on the growth rate and surface morphologies of oxide films during the anodizing process was discussed. It was found that hypochlorite ions participated in the reaction on anode which causes the rapid growth of oxide films and then affect the whole anodizing process.展开更多
An integrated low temperature nitriding process for TC4（Ti6Al4V） has been developed and the effect on wear resistance has been investigated. Through the process of solid solution strengthening—cold deformation—nit...An integrated low temperature nitriding process for TC4（Ti6Al4V） has been developed and the effect on wear resistance has been investigated. Through the process of solid solution strengthening—cold deformation—nitriding at 400℃, the TC4 alloy is nitrided on surface and dispersion strengthened in bulk at the same time. The white nitriding layer is formed after some time of nitriding. The nitriding speed increases with the deformation degree. The construction was investigated by XRD and the nitride is Ti3N（2-X）. The wear test was carried out and results exhibit that the nitrided samples have better wear resistance.展开更多
文摘Zirconium alloy(Zr-4)is extensively utilized in nuclear fuel cladding materials due to its exceptional neutron economy,high ductility,and promising corrosion and irradiation resistance.Nevertheless,during the operational lifespan of the Zr-4 fuel tube,micro-oscillations induced by the high-speed flow of cooling water can cause wear between the cladding tube and grids.This leads to wear failure of the Zr-4 alloy tube,which seriously threatens the safe operation of nuclear stations.The application of protective coatings onto the surface of zirconium alloys serves to enhance their resistance against wear,while without changing of the existing reactor structure.In this study,FeCrAl/CrN and FeCrAl coatings were fabricated on the surface of Zr-4 alloy using dual-target co-sputtering technology.The effects of the CrN interlayer on the microstructure,mechanical properties,and tribological behavior of FeCrAl coating in air and B-Li water were investigated,and a comparative analysis with Zr-4 alloy was conducted.The results showed that the application of FeCrAl/CrN and FeCrAl coatings significantly enhanced the hardness and wear resistance of Zr-4 alloy.The introduction of the CrN interlayer increased the columnar grain size of the FeCrAl coating and caused a change in the preferred growth direction of the coating from(110)to(211).The CrN interlayer improved the hardness and wear resistance of the coating,it also led to a decrease in adhesion strength.The wear rates of FeCrAl/CrN coatings in air and B-Li water were the lowest,about 3.2×10^(-6) mm^(3)/(N·m)and 6.0×10^(-7) mm^(3)/(N·m),respectively.The lubricating effect of B-Li water effectively reduced the friction coefficient and wear rate of both FeCrAl/CrN and FeCrAl coatings.In air and B-Li water,the primary wear mechanisms for Zr-4 are adhesive wear and oxidative wear,while the main wear mechanisms for FeCrAl/CrN and FeCrAl coatings are abrasive wear and oxidative wear.These findings not only provided a theoretical basis for understanding the microstructure and wear performance of FeCrAl coatings but also offered important technical guidance for their practical application in the nuclear industry.
文摘Aseries of [(Fe_(0.6)Co_(0.2)Ni_(0.2))_(0.75-0.03x)B_(0.2)Si_(0.05+0.03x)]_(96)Nb_(4) amorphous alloy composite coatings were prepared by adjusting the silicon content(x=0,1,2,3,4,5,and 6)and their microstructures and tribological properties were investigated by laser cladding technique.Additionally,the effect of Si on the glass forming ability(GFA)of the layers was understood.Results show that an appropriate Si content can refine the microstructure of the FeCoNiBSiNb laser cladding layers and improve the mechanical and tribological properties.The hardness of the coating layer increases monotonically with the Si content.At the Si content of 4.8at%(x=0),the coating layer exhibits a relatively low hardness(734.2HV 0.1).Conversely,at the silicon content of 13.44at%(x=3),the coating layer exhibits the highest hardness(1106HV 0.1).The non-crystalline content and tensile strength exhibit an initial increase,followed by a subsequent decrease.At x=2,the coating exhibits its maximum fracture strength(2880 MPa).However,when x>2,the fracture strength of the coating decreases with an increase in x.Conversely,with an increase in Si content,the wear volume loss initially decreases and then increases.At a Si content of 10.56at%(x=2),the coating exhibits the highest non-crystalline content(42%),the highest tensile strength(2880 MPa),and the most favorable dry friction performance.
基金Project(51674304) supported by the National Natural Science Foundation of ChinaProject(19B430013) supported by the Key Scientific Research Projects of Higher Education Institutions in Henan Province,ChinaProject(2017BSJJ013) supported by the Doctor Research Foundation of Zhengzhou University of Light Industry,China
文摘The tribological behaviors of Cu-15Ni-8Sn/graphite composites with the graphite content of 38 vol.%against AISI321 stainless steel under dry-sliding,deionized water and sea water were investigated on a block-on-ring configuration.The results indicated that the friction coefficient was the lowest under dry-sliding,and the highest in deionized water.The wear rate decreased to reach the minimum value of 1.39×10-15 m^(3)/(N·m)in sea water and in deionized water,it increased to the maximum value of 5.56×10-15 m^(3)/(N·m).The deionized water hindered the formation of tribo-oxide layer and lubricating film,which resulted in the largest friction coefficient and wear rate.In sea water,however,the corrosion products comprised of oxides,hydroxides and chlorides were found on the worn surface,and the compacted layer composed of corrosion products and graphite played an important role in keeping the excellent wear resistance.It was elucidated that the tribological behaviors of Cu-15Ni-8Sn/graphite composite were powerful influenced by the friction environments.
基金Project(2007046) supported by High Technology Research Project of Jiangsu Province,China
文摘The cooperative effect of laser surface texturing(LST) and double glow plasma surface alloying on tribological performance of lubricated sliding contacts was investigated.A Nd:YAG laser was used to generate microdimples on steel surfaces. Dimples with the diameter of 150μm and the depth of 30-35μm distributed circumferentially on the disc surface.The alloying element Cr was sputtered to the laser texturing steel surface by double glow plasma technique.A deep diffusion layer with a thickness of 30μm and a high hardness of HV900 was formed in this alloy.Tribological experiments of three types of samples(smooth,texturing and texturing+alloying) were conducted with a ring-on-disc tribometer to simulate the face seal.It is found that,in comparison with smooth steel surfaces,the laser texturing samples significantly reduce the friction coefficient.Moreover,the lower wear rate of the sample treated with the two surface techniques is observed.
基金Project(51305023) supported by the National Natural Science Foundation of ChinaProject(FRF-GF-17-B20) supported by the Fundamental Research Funds for the Central Universities of China
文摘A numerical optimization approach based on the finite element(FE) simulation was used to design the optimum irregular gourd-shaped pattern parameters for generating the highest hydrodynamic pressure. Then the optimum parameters of the gourd-shaped surface texture were determined and the textures were processed on the stainless steel surface by the laser technology. The tribological performance of gourd-shaped surface texture was analyzed using the type of UMT2 tester, and compared with that of the regular circle surface texture and none-texture surface by considering the effect of sliding speeds and applied loads on the tribological performance. The results show that the compound factor n, the diameter ratio Dr and the texture depth Hd are more significant parameters and the optimum values are 0.618, 2.0 and 4 μm, respectively. In addition, irregular gourd-shaped surface texture with optimum parameters is the most effective in the friction reduction among the patterns investigated under different speeds and applied loads in this work. Moreover, better coordination and combination effect can be obtained by gourd-shaped surface texture. The main reason responsible for the results is the irregular symmetric nature of the gourd-shaped texture along the direction of lubricants flowing which can generate the higher fluid dynamic pressure.
基金Project(51965040)supported by the National Natural Science Foundation of ChinaProject(20181BAB206026)supported by the National Science Foundation of Jiangxi Province,China。
文摘The effects of hot extrusion and addition of Al_(2)O_(3p) on both microstructure and tribological behavior of 7075 composites were investigated via optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive spectrometry(EDS),and transmission electron microscopy(TEM).The experimental consequences reveal that the optimal addition of Al_(2)O_(3p) was 2 wt%.After hot extrusion,the Mg(Zn,Cu,Al)2 phases partially dissolve into the matrix and generate many uniformly distributed aging precipitation particles,the Al_(7)Cu_(2)Fe phases are squeezed and broken,and the Al_(2)O_(3p) become uniform distribution.The microhardness of as-extruded 2 wt%Al_(2)O_(3p)/7075 composites reaches HV 170.34,increased by 41.5%than as-cast composites.The wear rate of as-extruded 2 wt%Al_(2)O_(3p)/7075 composites is further lower than that of as-cast composites under the same condition.SEM-EDS analyses reveal that the reinforced wear resistance of composites can put down to the protective effect of the Al_(2)O_(3p) reinforced transition layer.After hot extrusion,the transition layer becomes stable,which determines the reinforced wear resistance of the as-extruded composites.
基金Projects(51775365,51405329) supported by the National Natural Science Foundation of ChinaProject(2015M570239) supported by the China Postdoctoral Science Foundation
文摘This work is aimed to study the effect of boron on wear resistance of Fe-Cr-B alloys containing different boron contents(0 wt%,5 wt%,7 wt%and 9 wt%)from room temperature(RT)to 800°C in order to explore their applications as high-temperature wear resistant mechanical parts.Additionally,the wear mechanism of alloys is evaluated.The tribological properties of alloys are systematically studied by using a ball-on-disc tribometer at 10 N and 0.20 m/s from RT to 800°C sliding against Si3N4 ceramic ball.The boron element greatly improves the wear resistance of specimens as compared with that of unreinforced specimen.The friction coefficients of specimens decrease with increasing of testing temperature.The wear rates of Fe-Cr-B alloys decrease firstly and then raise with the increase of boron content.The specific wear rates of specimens with boron are 1/10 of the unreinforced specimen.Fe-21wt%Cr-7wt%B keeps the best tribological properties at high temperature.
文摘Mechanical properties and tribological behavior of a novel cast heat resisting copper based alloy are investigated. The corresponding properties of a commercial aluminum bronze C95500 (ASTM B30) are compared with the alloy. The results show that the alloy possesses better mechanical properties and tribological behaviors than that of C95500 at elevated temperature. The tensile strength, elongation and hardness at 500℃ are 470MPa, 2.5% and HB220, respectively. The wear rate of the developed alloy at ambient and elevated temperature is about one sixth and one fortieth of that of C95500, respectively. The alloy is very suitable for ma nufacturing heat resisting and wear resisting parts. Major strengthening mechanisms for the alloy are solution strengthening and the second phase strengthening.
文摘Ni/n-SiO2 composite coating was electrodeposited by brush-plating with pulse-reverse current（RC）. The morphology, hardness, and tribological properties of the coating were investigated and compared with those of Ni and composite coatings electrodeposited with direct current（DC）. The results indicate that Ni/n-SiO2 composite coating electrodeposited by RC, because of RC and the nano powders, has denser coating, finer crystal grains, higher hardness（HV650.0, nearly 1.5 times higher than that of Ni coating electrodeposited by DC） and lower friction coefficient（nearly 0.62）, as a result, in the wearing experiment, the Ni/n-SiO2 composite coating electrodeposited by RC has the least worn loss. So this kind of coating has better wear resistance. And RC electro brush-plating can be used as a new technology of brush-plating in the area of wear resistance.
基金Project(51165022)supported by the National Natural Science Foundation of ChinaProject(20122117)supported by the Lanzhou Science and Technology Bureau Foundation,ChinaProject(1310RJZA036)supported by the Natural Science Foundation of Gansu Province,China
文摘Nanoparticles are increasingly being used to improve the friction and wear performance of polymers. In this study, we investigated the tribological behavior and energy dissipation characteristics of nano-Al_2O_3-reinforced polytetrafluoroethylenepolyphenylene sulfide(PTFE-PPS) composites in a sliding system. The tribological behaviors of the composites were evaluated under different normal loads(100–300 N) at a high linear velocity(2 m/s) using a block-on-ring tester. Addition of the nano-Al_2O_3 filler improved the antiwear performance of the PTFE-PPS composites, and the friction coefficient increased slightly. The lowest wear rate was obtained when the nano-Al_2O_3 content was 3%(volume fraction). Further, the results indicated a linear correlation between wear and the amount of energy dissipated, even though the wear mechanism changed with the nano-Al_2O_3 content, independent of the normal load applied.
文摘To improve the solid lubricity on the worn surface of frictional-pairs, a convenient and simple brush-painting technique was utilized to prepare the solid lubrication graphite coatings. The bonding between the coatings and substrate is good. To examine the influence of the different graphite contents on the tribological properties of the graphite coatings, the comparison experiments were carried out on the ring-on-block friction tester. The tribological results show a change law of saddle-shape between the tribological properties of graphite coatings and graphite content. When the amount of graphite is up to 28g, the tribological properties of graphite coating are the best. The excellent anti-friction of the graphite coating is associated with the close-packed hexagonal crystal structure of graphite.
文摘Nanostructured n-Al2O3/Ni feedstock for thermal spraying was manufactured by the method of chemical wrapping and spray drying. The nanostructured coating was sprayed with this feedstock. Tribological properties of the coatings and steel 45# were tested. Within the testing range, the friction coefficient of coatings against GCr15 steel decreased and the mass loss of coatings increased at first then decreased with the increase of load. Under each load, the coatings’ friction coefficients and wear losses were lower than that of steel 45#. Scanning electron microscopy and energy dispersive spectrometer analysis show that adhesion is the dominating wear mechanism, and fatigue exists at the same time. Material transferred from counter-part to the coating is the main factor which influences the coatings’ friction coefficient and wear losses.
文摘The frictional properties of micro bearings have strong influence on the performance of the whole system because of tiny scale of micro-electromechanical system (MEMS). To develop micro bearings with low friction,it is important to evaluate the friction behaviors on the micro bearing. The testing system and the principle to evaluate the tribological performance of micromachining work-pieces under the load of mill Newton scale is introduced in paper "A new approach to measure the friction coefficient of micro journal bearings" of Yao et al,. But as the tribological force is faint in micro scale, the measured force is influenced a lot by the testing error. As the equation of that of Yao’s paper is very sensitive to the measured force, the tested result is influenced remarkably by testing error. So it is hard to get precision result. To solve this problem, the test system with new compensation method is introduced to precisely evaluate tribological performance under mill scale. The new metrology method is developed by means of the error compensation from two sets of testing data. The data are the force collected respectively when the friction counterparts rotate in CW(clockwise) and CCW(counter-clockwise) direction. So we deduce the equation of friction coefficient respctively on the condition of journal running in CCW and CW direction. As condition of measuring those two friciton coefficients are alike except the running direction of journal, and then the friction coefficient should be the same because this difference of direction has no influence on the fricition coefficients. Considering this, we unite the both equation, make the data measured in different subtract each other in the equation, and then a new equation can be gotten. This new equation enhances the metrology precision of friction coefficient theoretically thanks to the counteracting of error values in the equation. Using this method we testing the friction of high speed steel journal with hard alloy bearing. The result shows the new compensation method has better precision and repetition than CW and CCW method thanks to the error resistance.
文摘Through using mineral oil and synthetic oil to deploy the semisynthesis base oil, modifying the surfaces of ultrafine tungsten disulfide grains by surface chemical embellishment and adsorption embellishment to make them suspended steadily in the base oil as solid lubricating additive, and adding some function additives, the tungsten disulfide motor oil was prepared. The tribological characteristics of this kind motor oil and the well-known motor oils in our country and overseas were studied. The results show that the oil film strength of this kind of motor oil is respectively 1.06 and 1.38 times of that of shell helix ultra motor oil and great wall motor oil, and its sintering load is 1.75 and 2.33 times of that of them, and when tested under 392 N, 1 450 r/rain and 30 min, the friction coefficients of friction pairs lubricated by the tungsten disulfide motor oil decrease with the increase of time, meanwhile, the diameter of worn spot is small, and the surface of worn spot is smooth, and no obvious furrows appear. The experiments indicate that the tungsten disulfide motor oil has the better antiwear, antifriction and extreme pressure properties than the well-known motor oils.
文摘Non lubricated slide performance of functional grade copper matrix composite,fabricated using horizontal centrifuge cast technique was investigated using pin-on-disc tribo-tester.Rate of wear and friction coefficient of the inner wall thickness of hollow cylindrical cast specimen was analyzed using Taguchi based L27 orthogonal array,where the percentage of graphite particles were observed higher.Variable process parameters those influenced the rate of wear directly or indirectly were:applied load(15,25 and 35 N),slide velocity(1.5,2.5 and 3.5 m/s)and slide distance(750,1500 and 2250 m).Rate of wear and friction coefficient showed a proportional dependency with applied load and slide distance,whereas showing a decline during intermediate slide velocity.Signal-to-Noise ratio predicted the minimal tribo-condition,on‘smaller-the-better’basis.Analysis of Variance technique quantified the influence of affecting parameters,along with their interactions.Regression analysis was utilized for the validation of the experimental data.Micrographs and scanning electron microscopy exhibited the wear mechanisms and mechanically mixed layer formation during worn surfaces analysis.
文摘The aim of present study is to analyze the influence of volume percentage(vol.%) of nano-sized particles(TiB_2: average size is 35 nm) on microstructure, mechanical and tribological behavior of 6061-T6 Al alloy surface nano composite prepared via Friction stir process(FSP). The microstructure of the fabricated surface nanocomposites is examined using optical microscopy(OM) and scanning electron microscope(SEM) for distribution of TiB_2 nano reinforcement particles, thickness of nano composite layer formed on the Aluminum alloy substrate and fracture features. The depth of surface nano composite layer is measured as 3683.82 m m along the cross section of stir zone of nano composite perpendicular to FSP. It was observed that increase in volume percentage of TiB_2 particles, the microhardness is increased up to132 Hv and it is greater than as-received Al alloy's microhardness(104 Hv). It is also observed that at 4volume percentage higher tensile properties exhibited as compared with the 2 and 8 vol. %. It is found that high wear resistance exhibited at 4 volume percentage as-compared with the 2 and 8 vol. %. The observed wear and mechanical properties are interrelated with microstructure, fractography and worn morphology.
文摘Despite the great achievements made in improvement of wear resistance properties of aluminum alloys, their applications in heavy surface load-bearing are limited. Single coating is insufficient to produce the desired combination of surface properties. These problems can be solved through the duplex coatings. The aim of the present study is to overview the research advances on processes of duplex coatings on (aluminum) alloys combined with micro plasma oxidation process and with other modern processes such as physical vapour deposition and plasma assisted chemical vapour deposition and also to evaluate the performance of micro plasma oxidation coatings in improving the load-bearing, friction and wear resistance properties of aluminum alloys in comparison with other coatings. Wherein, a more detailed presentation of the processes and their performances and disadvantages are given as well.
文摘Oleic acid surface-modified Cu nanoparticles with an average size of 20 nm were prepared by liquid phase reducing reaction. The tribological performance and mechanism of nanocopper as additive were studied by means of tribotester, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and nanoindentation instrument. The results indicate that the modified nanocopper additive can significantly improve the wear resistance and reduce friction coefficient of base oil. A copper protective film is formed and contributes to the excellent tribological properties of nanocopper additive. On the basis of the film forming mechanism, a new in-situ repair method was designed and used to repair wear-out-failure injection pump plunger and barrel. Furthermore, the current research progress of nanoparticles as green energy-saving lubricating oil additives were presented.
基金Project(51271012)supported by the National Natural Science Foundation of China
文摘Anodic films were successfully fabricated on Ti6A14V alloy by anodic oxidation method in an environmental friendly electrolyte with and without sodium hypochlorite. The anodic films were characterized by means of the scanning electron microscope （SEM） and energy dispersive spectrometer （EDS）. Results revealed that the addition of sodium hypochlorite leads to the ultrafast growth of oxide films, and results in the significant changes of morphology and thickness. The influence of sodium hypochlorite on formation and crystallization of oxide films as a function of anodizing time was discussed. Meanwhile, potentiodynamic electrochemical tests and dry sliding wear tests were performed to evaluate the corrosion resistance and tribological properties of oxide films. It was found that the oxide film fabricated with the existence of sodium hypochlorite had improved corrosion resistance and tribological properties than the one formed without sodium hypochlorite. Moreover, the effect mechanism of sodium hypochlorite on the growth rate and surface morphologies of oxide films during the anodizing process was discussed. It was found that hypochlorite ions participated in the reaction on anode which causes the rapid growth of oxide films and then affect the whole anodizing process.
基金Projects(51275105,51375106)supported by the National Natural Science Foundation of China
文摘An integrated low temperature nitriding process for TC4（Ti6Al4V） has been developed and the effect on wear resistance has been investigated. Through the process of solid solution strengthening—cold deformation—nitriding at 400℃, the TC4 alloy is nitrided on surface and dispersion strengthened in bulk at the same time. The white nitriding layer is formed after some time of nitriding. The nitriding speed increases with the deformation degree. The construction was investigated by XRD and the nitride is Ti3N（2-X）. The wear test was carried out and results exhibit that the nitrided samples have better wear resistance.
