A diamond-like carbon（DLC） film was deposited on YT14 substrate using magnetron sputtering（MS）. The surface morphologies, roughness and bonding spectra of obtained film were characterized using scanning electron m...A diamond-like carbon（DLC） film was deposited on YT14 substrate using magnetron sputtering（MS）. The surface morphologies, roughness and bonding spectra of obtained film were characterized using scanning electron microscopy（SEM）, atomic force microscopy（AFM）, and X-ray photoelectron spectroscopy（XPS）, respectively, and its mechanical property and bonding strength were measured using a nanoindentation and scratch tester, respectively. The results show that the C-enriched DLC film exhibits a denser microstructure and smoother surface with lower surface roughness of 21.8 nm. The ratio of C sp2 at 284.4 e V that corresponds to the diamond（111） and the C sp3 at 285.3 e V that corresponds to the diamond（220） plane for the as-received film is 0.36： 0.64, showing that the C sp3 has the high content. The hardness and Young＇s modulus of DLC film by nanoindentation are 8.534 41 and 142.158 1 GPa, respectively, and the corresponding bonding strength is 74.55 N by scratch test.展开更多
Composite SiNx/DLC films were deposited on Si substrate by RF magnetron sputtering of silicon nitride (Si3N4) target simultaneously with filtered cathode arc (FCA) of graphite. The RF power was fixed at 100 W whereas ...Composite SiNx/DLC films were deposited on Si substrate by RF magnetron sputtering of silicon nitride (Si3N4) target simultaneously with filtered cathode arc (FCA) of graphite. The RF power was fixed at 100 W whereas the arc currents of FCA were 20, 40, 60 and 80 A. The effects of arc current on the structure, surface roughness, density and mechanical properties of SiNx/DLC films were investigated. The results show that the arc current in the studied range has effect on the structure, surface roughness, density and mechanical properties of composite SiNx/DLC films. The composite SiNx/DLC films show the sp3 content between 53.5% and 66.7%, density between 2.54 and2.98 g/cm3, stress between 1.7 and 2.2 GPa, and hardness between 35 and 51 GPa. Furthermore, it was found that the density, stress and hardness correlate linearly with the sp3 content for composite SiNx/DLC films.展开更多
Platinum(Pt)and nitrogen(N)were co-incorporated in diamond-like carbon(DLC)thin films using a magnetron sputtering system to form PtN-DLC thin films for tribological applications.The Pt content in the PtN-DLC films pr...Platinum(Pt)and nitrogen(N)were co-incorporated in diamond-like carbon(DLC)thin films using a magnetron sputtering system to form PtN-DLC thin films for tribological applications.The Pt content in the PtN-DLC films prepared on Si substrates was controlled by varying RF power applied to a Pt target at a fixed N2 flow rate.The tribological properties of the PtN-DLC films were investigated with respect to the Pt content in the films.The uncoated Si substrate surface tested against a steel ball of 6 mm in diameter had significant abrasive and fatigue wear,while no significant wear was found on the N-DLC coated sample surface,indicating that the N-DLC film effectively prevented its underlying Si substrate from wear.However,the incorporation of Pt in the N-DLC films reduced the wear resistance of the films by degrading sp3-bonded cross-linking structures of the films so that significant wear tracks were found on the surfaces of the PtN-DLC films.Therefore,the increased radio frequency(RF)power applied to the Pt target decreased the wear resistance of the PtN-DLC films as a result of the increased Pt content.展开更多
It is imperative to develop a novel matching of metallic substrate and self-lubricating coating for aircraft spherical plain bearing in a wide range of service conditions.As a new type of superelastic material,60NiTi ...It is imperative to develop a novel matching of metallic substrate and self-lubricating coating for aircraft spherical plain bearing in a wide range of service conditions.As a new type of superelastic material,60NiTi alloy meets the performance requirements of aerospace bearing materials,but exhibits poor tribological performance,especially under the conditions of dry sliding friction.A Hydrogenated Diamond-Like Carbon(H-DLC)coating was deposited on the 60NiTi alloy to improve its tribological performance.The microstructure and mechanical behavior of the 60NiTi alloy and its H-DLC coating were explored.Results show that improvement of friction and wear performance of the H-DLC coating deposited on the 60NiTi substrate is mainly achieved by graphitization at the friction interface and the transfer film produced on the counterpart ball.The increased friction load leads to intensification of graphitization at the friction interface and formation of continuous and compact transfer film on the surface of the counterpart ball.展开更多
In this study,we mainly focus on the structural morphology and inter-atomic bonding state of tribofilms resulting from a highly-hydrogenated amorphous carbon(a-C:H) film in order to ascertain the underlying mechanisms...In this study,we mainly focus on the structural morphology and inter-atomic bonding state of tribofilms resulting from a highly-hydrogenated amorphous carbon(a-C:H) film in order to ascertain the underlying mechanisms for its superlubric behavior(i.e.,less than 0.01 friction coefficient).Specifically,we achieved superlubricity(i.e.,friction coefficients of down to 0.003) with this film in dry nitrogen and argon atmospheres especially when the tribo-pair is made of an a-C:H coated Si disk sliding against an a-C:H coated steel ball,while the a-C:H coated disk against uncoated ball does not provide superlubricity.We also found that the state of superlubricity is more stable in argon than in nitrogen and the formation of a smooth and uniformly-thick carbonaceous tribofilm appears to be one of the key factors for the realization of such superlubricity.Besides,the interfacial morphology of sliding test pairs and the atomic-scale bond structure of the carbon-based tribofilms also play an important role in the observed superlubric behavior of a-C:H films.Using Raman spectroscopy and high resolution transmission electron microscopy,we have compared the structural differences of the tribofilms produced on bare and a-C:H coated steel balls.For the a-C:H coated ball as mating material which provided superlow friction in argon,structural morphology of the tribofilm was similar or comparable to that of the original a-C:H coating;while for the bare steel ball,the sp^2-bonded C fraction in the tribofilm increased and a fingerprint-like nanocrystalline structure was detected by high resolution transmission electron microscopy(HRTEM).We also calculated the shear stresses for different tribofilms,and established a relationship between the magnitude of the shear stresses and the extent of sp^3-sp^2 phase transformation.展开更多
High-performance diamond films are highly demanded on tool surfaces for wire-drawing and mechanical sealing applications.Herein,this work aims at enhancing the tribological performance of chemical vapor deposition dia...High-performance diamond films are highly demanded on tool surfaces for wire-drawing and mechanical sealing applications.Herein,this work aims at enhancing the tribological performance of chemical vapor deposition diamond films in water-lubricated conditions by utilizing non-hydrogenated and hydrogenated diamond-like carbon(DLC and DLC-H)top layers.The tribological properties of bilayer micro-crystalline diamond(MCD)/DLC,MCD/DLC-H,nano-crystalline diamond(NCD)/DLC and NCD/DLC-H films are evaluated,in terms of maximal and stable coefficients of friction(COFs),C—C bonds transformation,worn surface morphology and specific wear rates.The results show that DLC or DLC-H coated on diamond layer significantly suppresses the initial maximal COF peak and the wear of counterpart ball.Moreover,severe regular arranged sp^(2) C—C bonds transformation is detected on MCD film,in comparison to NCD;while inversely,the NCD/DLC bilayer exhibits severer C—C bonds transformation effect compared with the MCD/DLC.Furthermore,the DLC-H top layer shows a larger decreasing rate of maximal COFs and wear rates of counterpart balls,compared with the DLC coating,which is due to its superior self-lubricity.Among all the tested films,the NCD/DLC-H bilayer shows an optimized tribological performance.展开更多
Diamond-like carbon(DLC)films are deposited on rubber surfaces to protect the rubber components,and surface pretreatment of the rubber substrates prior to the film deposition can improve the adhesion between the DLC f...Diamond-like carbon(DLC)films are deposited on rubber surfaces to protect the rubber components,and surface pretreatment of the rubber substrates prior to the film deposition can improve the adhesion between the DLC films and the rubber.Thus,the principal purpose of this work concentrates on determining the effects of argon(Ar),oxygen(O_(2)),nitrogen(N_(2)),and hydrogen(H_(2))plasma pretreatments on the adhesion and friction performance of the DLC films deposited on rubber(DLC/rubber).The results indicated that the Ar plasma pretreatment promoted the formation of a compact layer on the rubber surface.By contrast,massive fillers were exposed on the rubber surface after oxygen or nitrogen plasma pretreatments.Moreover,the typical micrometer-scale patches divided by random cracks were observed on the surface of DLC/rubber,except for the sample pretreated with oxygen plasma.The adhesion of DLC/rubber was found to strengthen with the removal of weak boundary layers and the generation of free radicals on the rubber surface after plasma pretreatment.The tribo-tests revealed that DLC/rubber with O_(2),N_(2),and H_(2) plasma pretreatments cannot achieve optimal friction performance.Significantly,DLC/rubber with Ar plasma pretreatment exhibited a low and stable friction coefficient of 0.19 and superior wear resistance,which was correlated to the high adhesion,good load-bearing of the rubber surface,and the approximate sine function of the surface profile of the DLC film.展开更多
Diamond-like carbon(DLC)film has been developed as an extremely effective lubricant to reduce energy dissipation;however,most films should undergo running-in to achieve a super-low friction state.In this study,the run...Diamond-like carbon(DLC)film has been developed as an extremely effective lubricant to reduce energy dissipation;however,most films should undergo running-in to achieve a super-low friction state.In this study,the running-in behaviors of an H–DLC/Al_(2)O_(3) pair were investigated through a controllable single-asperity contact study using an atomic force microscope.This study presents direct evidence that illustrates the role of transfer layer formation and oxide layer removal in the friction reduction during running-in.After 200 sliding cycles,a thin transfer layer was formed on the Al2O3 tip.Compared with a clean tip,this modified tip showed a significantly lower adhesion force and friction force on the original H–DLC film,which confirmed the contribution of the transfer layer formation in the friction reduction during running-in.It was also found that the friction coefficient of the H–DLC/Al_(2)O_(3) pair decreased linearly as the oxygen concentration of the H–DLC substrate surface decreased.This phenomenon can be explained by a change in the contact surface from an oxygen termination with strong hydrogen bond interactions to a hydrogen termination with weak van der Waals interactions.These results provide new insights that quantitatively reveal the running-in mechanism at the nanoscale,which may help with the design optimization of DLC films for different environmental applications.展开更多
基金Funded by the Jiangsu Province Science and Technology Support Program(Industry)(No.BE2014818)
文摘A diamond-like carbon（DLC） film was deposited on YT14 substrate using magnetron sputtering（MS）. The surface morphologies, roughness and bonding spectra of obtained film were characterized using scanning electron microscopy（SEM）, atomic force microscopy（AFM）, and X-ray photoelectron spectroscopy（XPS）, respectively, and its mechanical property and bonding strength were measured using a nanoindentation and scratch tester, respectively. The results show that the C-enriched DLC film exhibits a denser microstructure and smoother surface with lower surface roughness of 21.8 nm. The ratio of C sp2 at 284.4 e V that corresponds to the diamond（111） and the C sp3 at 285.3 e V that corresponds to the diamond（220） plane for the as-received film is 0.36： 0.64, showing that the C sp3 has the high content. The hardness and Young＇s modulus of DLC film by nanoindentation are 8.534 41 and 142.158 1 GPa, respectively, and the corresponding bonding strength is 74.55 N by scratch test.
文摘Composite SiNx/DLC films were deposited on Si substrate by RF magnetron sputtering of silicon nitride (Si3N4) target simultaneously with filtered cathode arc (FCA) of graphite. The RF power was fixed at 100 W whereas the arc currents of FCA were 20, 40, 60 and 80 A. The effects of arc current on the structure, surface roughness, density and mechanical properties of SiNx/DLC films were investigated. The results show that the arc current in the studied range has effect on the structure, surface roughness, density and mechanical properties of composite SiNx/DLC films. The composite SiNx/DLC films show the sp3 content between 53.5% and 66.7%, density between 2.54 and2.98 g/cm3, stress between 1.7 and 2.2 GPa, and hardness between 35 and 51 GPa. Furthermore, it was found that the density, stress and hardness correlate linearly with the sp3 content for composite SiNx/DLC films.
文摘Platinum(Pt)and nitrogen(N)were co-incorporated in diamond-like carbon(DLC)thin films using a magnetron sputtering system to form PtN-DLC thin films for tribological applications.The Pt content in the PtN-DLC films prepared on Si substrates was controlled by varying RF power applied to a Pt target at a fixed N2 flow rate.The tribological properties of the PtN-DLC films were investigated with respect to the Pt content in the films.The uncoated Si substrate surface tested against a steel ball of 6 mm in diameter had significant abrasive and fatigue wear,while no significant wear was found on the N-DLC coated sample surface,indicating that the N-DLC film effectively prevented its underlying Si substrate from wear.However,the incorporation of Pt in the N-DLC films reduced the wear resistance of the films by degrading sp3-bonded cross-linking structures of the films so that significant wear tracks were found on the surfaces of the PtN-DLC films.Therefore,the increased radio frequency(RF)power applied to the Pt target decreased the wear resistance of the PtN-DLC films as a result of the increased Pt content.
基金co-supported by the National Natural Science Foundation of China(No.51905466)the Aeronautical Science Foundation of China(No.201945099002)+1 种基金the Natural Science Foundation of Hebei Province,China(Nos.E2021203191 and E2020203184)the Youth Top Talent Project of Hebei Province Higher Education,China(No.BJ2019058).
文摘It is imperative to develop a novel matching of metallic substrate and self-lubricating coating for aircraft spherical plain bearing in a wide range of service conditions.As a new type of superelastic material,60NiTi alloy meets the performance requirements of aerospace bearing materials,but exhibits poor tribological performance,especially under the conditions of dry sliding friction.A Hydrogenated Diamond-Like Carbon(H-DLC)coating was deposited on the 60NiTi alloy to improve its tribological performance.The microstructure and mechanical behavior of the 60NiTi alloy and its H-DLC coating were explored.Results show that improvement of friction and wear performance of the H-DLC coating deposited on the 60NiTi substrate is mainly achieved by graphitization at the friction interface and the transfer film produced on the counterpart ball.The increased friction load leads to intensification of graphitization at the friction interface and formation of continuous and compact transfer film on the surface of the counterpart ball.
基金supported by the National Basic Research Program of China (Grant No.2011CB013404)National Natural Science Foundation of China(Grant Nos.51321092,51527901 and 51375010)
文摘In this study,we mainly focus on the structural morphology and inter-atomic bonding state of tribofilms resulting from a highly-hydrogenated amorphous carbon(a-C:H) film in order to ascertain the underlying mechanisms for its superlubric behavior(i.e.,less than 0.01 friction coefficient).Specifically,we achieved superlubricity(i.e.,friction coefficients of down to 0.003) with this film in dry nitrogen and argon atmospheres especially when the tribo-pair is made of an a-C:H coated Si disk sliding against an a-C:H coated steel ball,while the a-C:H coated disk against uncoated ball does not provide superlubricity.We also found that the state of superlubricity is more stable in argon than in nitrogen and the formation of a smooth and uniformly-thick carbonaceous tribofilm appears to be one of the key factors for the realization of such superlubricity.Besides,the interfacial morphology of sliding test pairs and the atomic-scale bond structure of the carbon-based tribofilms also play an important role in the observed superlubric behavior of a-C:H films.Using Raman spectroscopy and high resolution transmission electron microscopy,we have compared the structural differences of the tribofilms produced on bare and a-C:H coated steel balls.For the a-C:H coated ball as mating material which provided superlow friction in argon,structural morphology of the tribofilm was similar or comparable to that of the original a-C:H coating;while for the bare steel ball,the sp^2-bonded C fraction in the tribofilm increased and a fingerprint-like nanocrystalline structure was detected by high resolution transmission electron microscopy(HRTEM).We also calculated the shear stresses for different tribofilms,and established a relationship between the magnitude of the shear stresses and the extent of sp^3-sp^2 phase transformation.
基金the National Natural Science Foundation of China(No.51705155)the Tribology Science Fund of State Key Laboratory of Tribology(No.SKLTKF17B09)。
文摘High-performance diamond films are highly demanded on tool surfaces for wire-drawing and mechanical sealing applications.Herein,this work aims at enhancing the tribological performance of chemical vapor deposition diamond films in water-lubricated conditions by utilizing non-hydrogenated and hydrogenated diamond-like carbon(DLC and DLC-H)top layers.The tribological properties of bilayer micro-crystalline diamond(MCD)/DLC,MCD/DLC-H,nano-crystalline diamond(NCD)/DLC and NCD/DLC-H films are evaluated,in terms of maximal and stable coefficients of friction(COFs),C—C bonds transformation,worn surface morphology and specific wear rates.The results show that DLC or DLC-H coated on diamond layer significantly suppresses the initial maximal COF peak and the wear of counterpart ball.Moreover,severe regular arranged sp^(2) C—C bonds transformation is detected on MCD film,in comparison to NCD;while inversely,the NCD/DLC bilayer exhibits severer C—C bonds transformation effect compared with the MCD/DLC.Furthermore,the DLC-H top layer shows a larger decreasing rate of maximal COFs and wear rates of counterpart balls,compared with the DLC coating,which is due to its superior self-lubricity.Among all the tested films,the NCD/DLC-H bilayer shows an optimized tribological performance.
基金carried out in Youth Innovation Promotion Association CAS(No.2017459)the National Natural Science Foundation of China(Nos.U1737213 and 51911530114).
文摘Diamond-like carbon(DLC)films are deposited on rubber surfaces to protect the rubber components,and surface pretreatment of the rubber substrates prior to the film deposition can improve the adhesion between the DLC films and the rubber.Thus,the principal purpose of this work concentrates on determining the effects of argon(Ar),oxygen(O_(2)),nitrogen(N_(2)),and hydrogen(H_(2))plasma pretreatments on the adhesion and friction performance of the DLC films deposited on rubber(DLC/rubber).The results indicated that the Ar plasma pretreatment promoted the formation of a compact layer on the rubber surface.By contrast,massive fillers were exposed on the rubber surface after oxygen or nitrogen plasma pretreatments.Moreover,the typical micrometer-scale patches divided by random cracks were observed on the surface of DLC/rubber,except for the sample pretreated with oxygen plasma.The adhesion of DLC/rubber was found to strengthen with the removal of weak boundary layers and the generation of free radicals on the rubber surface after plasma pretreatment.The tribo-tests revealed that DLC/rubber with O_(2),N_(2),and H_(2) plasma pretreatments cannot achieve optimal friction performance.Significantly,DLC/rubber with Ar plasma pretreatment exhibited a low and stable friction coefficient of 0.19 and superior wear resistance,which was correlated to the high adhesion,good load-bearing of the rubber surface,and the approximate sine function of the surface profile of the DLC film.
基金The authors are grateful for the financial support from the National Natural Science Foundation of China(51875486 and 51991373)Sichuan Science and Technology Program(2019YFH0098).
文摘Diamond-like carbon(DLC)film has been developed as an extremely effective lubricant to reduce energy dissipation;however,most films should undergo running-in to achieve a super-low friction state.In this study,the running-in behaviors of an H–DLC/Al_(2)O_(3) pair were investigated through a controllable single-asperity contact study using an atomic force microscope.This study presents direct evidence that illustrates the role of transfer layer formation and oxide layer removal in the friction reduction during running-in.After 200 sliding cycles,a thin transfer layer was formed on the Al2O3 tip.Compared with a clean tip,this modified tip showed a significantly lower adhesion force and friction force on the original H–DLC film,which confirmed the contribution of the transfer layer formation in the friction reduction during running-in.It was also found that the friction coefficient of the H–DLC/Al_(2)O_(3) pair decreased linearly as the oxygen concentration of the H–DLC substrate surface decreased.This phenomenon can be explained by a change in the contact surface from an oxygen termination with strong hydrogen bond interactions to a hydrogen termination with weak van der Waals interactions.These results provide new insights that quantitatively reveal the running-in mechanism at the nanoscale,which may help with the design optimization of DLC films for different environmental applications.
