Diamond-like carbon(DLC)coatings are known to provide beneficial mechanical and tribological properties in harsh environments.Their combination of high wear resistance and low friction has led to their extensive use i...Diamond-like carbon(DLC)coatings are known to provide beneficial mechanical and tribological properties in harsh environments.Their combination of high wear resistance and low friction has led to their extensive use in any number of industries.The tribological performance of a DLC coating is varied however,and the frictional response is known to be strongly dependent on the surrounding environment,as well as the material composition and bonding structure of the DLC coating.This paper presents an up-to-date review on the friction of DLC coatings in a water environment,with a special focus on transfer layer formation and tribochemistry.展开更多
Diamond-like carbon(DLC)and graphite-like carbon(GLC)coatings have good prospects for improving the surface properties of engine parts.However,further understanding is needed on the effect of working conditions on tri...Diamond-like carbon(DLC)and graphite-like carbon(GLC)coatings have good prospects for improving the surface properties of engine parts.However,further understanding is needed on the effect of working conditions on tribological behaviors.In this study,GLC and two types of DLC coatings were deposited on GCr15 substrate for investigation.The friction and wear properties of self-mated and steel-mated pairs were evaluated.Two temperatures(25 and 90℃),three lubrication conditions(base oil,molybdenum dithiocarbamate(MoDTC)-containing oil,MoDTC+zinc dialkyldithiophosphate(ZDDP)-containing oil),and high Hertz contact stress(2.41 GPa)were applied in the experiments.The results showed that high temperature promoted the effect of ZDDP on steel-mated pairs,but increased wear under base oil lubrication.The increased wear for steel-mated pairs lubricated by MoDTC-containing oil was due to abrasive wear probably caused by MoO_(3) andβ-FeMoO_(4).It was also found that in most cases,the tribological properties of self-mated pairs were better than those of steel-mated pairs.展开更多
In hydrodynamic bearings traditional bearing alloys:Babbitts and bronzes are most frequently utilized.Polymer sliding layers are sometimes applied as a valuable alternative.Hard diamond-like carbon(DLC)coatings,which ...In hydrodynamic bearings traditional bearing alloys:Babbitts and bronzes are most frequently utilized.Polymer sliding layers are sometimes applied as a valuable alternative.Hard diamond-like carbon(DLC)coatings,which are also considered for certain applications may show some advantages,as well.Although material selection is of secondary importance in a full film lubrication regime it becomes important in mixed friction conditions,which is crucial for bearings with frequent starts and stops.Experimental research aimed at studying the performance of fluid film bearings in the specific operating regime,including the transition to mixed friction,is described in the paper.The tests were carried out on four tilting pad bearings of different material compositions:Steel/bronze,DLC/steel,steel/polyether ether ketone(PEEK),and steel/Babbitt.The tests comprised stopping under load and reproduction of the Stribeck curve by decreasing rotational speed to very low values,and observing the changes of friction force during the transition to mixed friction regime.Analysis of the transition conditions and other results showed clear differences between the tested bearings,illustrating the feasibility of less popular material compositions for bearings operating in specific conditions.More specifically,the DLC/steel bearing was demonstrating superior performance,i.e.lower friction,transition to mixed friction occurring at higher load,and more stable performance at start-stop regime over the other tested bearings.展开更多
In this work, diamond-like carbon （DLC） films were deposited on stainless steel substrates with Si/SiC intermediate layers by combining plasma enhanced sputtering physical vapour deposition （PEUMS-PVD） and microwa...In this work, diamond-like carbon （DLC） films were deposited on stainless steel substrates with Si/SiC intermediate layers by combining plasma enhanced sputtering physical vapour deposition （PEUMS-PVD） and microwave electron cyclotron resonance plasma enhanced chemical vapour deposition （MW-ECRPECVD） techniques. The influence of substrate negative self-bias voltage and Si target power on the structure and nano-mechanical behaviour of the DLC films were investigated by Raman spectroscopy, nano-indentation, and the film structural morphology by atomic force microscopy （AFM）. With the increase of deposition bias voltage, the G band shifted to higher wave-number and the integrated intensity ratio ID/IG increased. We considered these as evidences for the development of graphitization in the films. As the substrate negative self-bias voltage increased, particle bombardment function was enhanced and the sp^3-bond carbon density reducing, resulted in the peak values of hardness （H） and elastic modulus （E）. Silicon addition promoted the formation of sp^3 bonding and reduced the hardness. The incorporated Si atoms substituted sp^2- bond carbon atoms in ring structures, which promoted the formation of sp^3-bond. The structural transition from C-C to C-Si bonds resulted in relaxation of the residual stress which led to the decrease of internal stress and hardness. The results of AFM indicated that the films was dense and homogeneous, the roughness of the films was decreased due to the increase of substrate negative self-bias voltage and the Si target power.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
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
Organic molybdenum lubricant additive like molybdenum dialkyl dithiocarbamate(MoDTC)can cause wear acceleration of diamond-like carbon(DLC)coating coupled with steel under boundary lubrication,which hinders its indust...Organic molybdenum lubricant additive like molybdenum dialkyl dithiocarbamate(MoDTC)can cause wear acceleration of diamond-like carbon(DLC)coating coupled with steel under boundary lubrication,which hinders its industrial application.Therefore,polyisobutylene succinimide(PIBS),an organo molybdenum amide,was adopted to modify molybdenum oxide affording molybdenum polyisobutylene succinimidemolybdenum oxide nanoparticles(MPIBS-MONPs)with potential to prevent the wear acceleration of DLC coating.The thermal stability of MPIBS-MONPs was evaluated by thermogravimetric analysis.Their tribological properties as the additives in di-isooctyl sebacate(DIOS)were evaluated with MoDTC as a control;and their tribomechanism was investigated in relation to their tribochemical reactions and synergistic tribological effect with zinc dialkyldithiophosphate(ZDDP)as well as worn surface characterizations.Findings indicate that MPIBS-MONPs/ZDDP added in DIOS can significantly reduce the friction and wear of DLC coating,being much superior to MoDTC.This is because MPIBS-MONPs and ZDDP jointly take part in tribochemical reactions to form a composite tribofilm that can increase the wear resistance of DLC coating.Namely,the molybdenum amide on MPIBS-MONPs surface can react with ZDDP to form MoS2 film with excellent friction-reducing ability;and MPIBS-MONPs can release molybdenum oxide nanoparticle to form deposited lubrication layer on worn surfaces.The as-formed composite tribofilm consisting of molybdenum oxide nanocrystal,amorphous polyphosphate,and molybdenum disulfide as well as a small amount of Mo2C accounts for the increase in the wear resistance of DLC coating under boundary lubrication.展开更多
To meet the surging needs in energy efficiency and eco-friendly lubricants,a novel superlubricious technology using a vegetable oil and ceramic materials is proposed.By coupling different hydrogen-free amorphous carbo...To meet the surging needs in energy efficiency and eco-friendly lubricants,a novel superlubricious technology using a vegetable oil and ceramic materials is proposed.By coupling different hydrogen-free amorphous carbon coatings with varying fraction of sp^(2) and sp^(3) hybridized carbon in presence of a commercially available silicon nitride bulk ceramic,castor oil provides superlubricity although the liquid vegetable oil film in the contact is only a few nanometres thick at most.Besides a partial liquid film possibly separating surfaces in contact,local tribochemical reactions between asperities are essential to maintain superlubricity at low speeds.High local pressure activates chemical degradation of castor oil generating graphitic/graphenic-like species on top of asperities,thus helping both the chemical polishing of surface and its chemical passivation by H and OH species.Particularly,the formation of the formation of–(CH_(2)–CH_(2))n–noligomers have been evidenced to have a major role in the friction reduction.Computer simulation unveils that formation of chemical degradation products of castor oil on friction surfaces are favoured by the quantity of sp^(2)-hybridized carbon atoms in the amorphous carbon structure.Hence,tuning sp^(2)-carbon content in hydrogen-free amorphous carbon,in particular,on the top layers of the coating,provides an alternative way to control superlubricity achieved with castor oil and other selected green lubricants.展开更多
文摘Diamond-like carbon(DLC)coatings are known to provide beneficial mechanical and tribological properties in harsh environments.Their combination of high wear resistance and low friction has led to their extensive use in any number of industries.The tribological performance of a DLC coating is varied however,and the frictional response is known to be strongly dependent on the surrounding environment,as well as the material composition and bonding structure of the DLC coating.This paper presents an up-to-date review on the friction of DLC coatings in a water environment,with a special focus on transfer layer formation and tribochemistry.
基金This work was supported by the Beijing Municipal Natural Science Foundation(3182032)the National Natural Science Foundation of China(41772389)+1 种基金the Pre-Research Program in National 13th Five-Year Plan(61409230603)Joint Fund of Ministry of Education for Pre-research of Equipment for Young Personnel Project(6141A02033120).
文摘Diamond-like carbon(DLC)and graphite-like carbon(GLC)coatings have good prospects for improving the surface properties of engine parts.However,further understanding is needed on the effect of working conditions on tribological behaviors.In this study,GLC and two types of DLC coatings were deposited on GCr15 substrate for investigation.The friction and wear properties of self-mated and steel-mated pairs were evaluated.Two temperatures(25 and 90℃),three lubrication conditions(base oil,molybdenum dithiocarbamate(MoDTC)-containing oil,MoDTC+zinc dialkyldithiophosphate(ZDDP)-containing oil),and high Hertz contact stress(2.41 GPa)were applied in the experiments.The results showed that high temperature promoted the effect of ZDDP on steel-mated pairs,but increased wear under base oil lubrication.The increased wear for steel-mated pairs lubricated by MoDTC-containing oil was due to abrasive wear probably caused by MoO_(3) andβ-FeMoO_(4).It was also found that in most cases,the tribological properties of self-mated pairs were better than those of steel-mated pairs.
文摘In hydrodynamic bearings traditional bearing alloys:Babbitts and bronzes are most frequently utilized.Polymer sliding layers are sometimes applied as a valuable alternative.Hard diamond-like carbon(DLC)coatings,which are also considered for certain applications may show some advantages,as well.Although material selection is of secondary importance in a full film lubrication regime it becomes important in mixed friction conditions,which is crucial for bearings with frequent starts and stops.Experimental research aimed at studying the performance of fluid film bearings in the specific operating regime,including the transition to mixed friction,is described in the paper.The tests were carried out on four tilting pad bearings of different material compositions:Steel/bronze,DLC/steel,steel/polyether ether ketone(PEEK),and steel/Babbitt.The tests comprised stopping under load and reproduction of the Stribeck curve by decreasing rotational speed to very low values,and observing the changes of friction force during the transition to mixed friction regime.Analysis of the transition conditions and other results showed clear differences between the tested bearings,illustrating the feasibility of less popular material compositions for bearings operating in specific conditions.More specifically,the DLC/steel bearing was demonstrating superior performance,i.e.lower friction,transition to mixed friction occurring at higher load,and more stable performance at start-stop regime over the other tested bearings.
文摘In this work, diamond-like carbon （DLC） films were deposited on stainless steel substrates with Si/SiC intermediate layers by combining plasma enhanced sputtering physical vapour deposition （PEUMS-PVD） and microwave electron cyclotron resonance plasma enhanced chemical vapour deposition （MW-ECRPECVD） techniques. The influence of substrate negative self-bias voltage and Si target power on the structure and nano-mechanical behaviour of the DLC films were investigated by Raman spectroscopy, nano-indentation, and the film structural morphology by atomic force microscopy （AFM）. With the increase of deposition bias voltage, the G band shifted to higher wave-number and the integrated intensity ratio ID/IG increased. We considered these as evidences for the development of graphitization in the films. As the substrate negative self-bias voltage increased, particle bombardment function was enhanced and the sp^3-bond carbon density reducing, resulted in the peak values of hardness （H） and elastic modulus （E）. Silicon addition promoted the formation of sp^3 bonding and reduced the hardness. The incorporated Si atoms substituted sp^2- bond carbon atoms in ring structures, which promoted the formation of sp^3-bond. The structural transition from C-C to C-Si bonds resulted in relaxation of the residual stress which led to the decrease of internal stress and hardness. The results of AFM indicated that the films was dense and homogeneous, the roughness of the films was decreased due to the increase of substrate negative self-bias voltage and the Si target power.
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support provided by the National Natural Science Foundation of China(Nos.51875172 and 52105180)Zhongyuan Science and Technology Innovation Leadership Program(No.214200510024).
文摘Organic molybdenum lubricant additive like molybdenum dialkyl dithiocarbamate(MoDTC)can cause wear acceleration of diamond-like carbon(DLC)coating coupled with steel under boundary lubrication,which hinders its industrial application.Therefore,polyisobutylene succinimide(PIBS),an organo molybdenum amide,was adopted to modify molybdenum oxide affording molybdenum polyisobutylene succinimidemolybdenum oxide nanoparticles(MPIBS-MONPs)with potential to prevent the wear acceleration of DLC coating.The thermal stability of MPIBS-MONPs was evaluated by thermogravimetric analysis.Their tribological properties as the additives in di-isooctyl sebacate(DIOS)were evaluated with MoDTC as a control;and their tribomechanism was investigated in relation to their tribochemical reactions and synergistic tribological effect with zinc dialkyldithiophosphate(ZDDP)as well as worn surface characterizations.Findings indicate that MPIBS-MONPs/ZDDP added in DIOS can significantly reduce the friction and wear of DLC coating,being much superior to MoDTC.This is because MPIBS-MONPs and ZDDP jointly take part in tribochemical reactions to form a composite tribofilm that can increase the wear resistance of DLC coating.Namely,the molybdenum amide on MPIBS-MONPs surface can react with ZDDP to form MoS2 film with excellent friction-reducing ability;and MPIBS-MONPs can release molybdenum oxide nanoparticle to form deposited lubrication layer on worn surfaces.The as-formed composite tribofilm consisting of molybdenum oxide nanocrystal,amorphous polyphosphate,and molybdenum disulfide as well as a small amount of Mo2C accounts for the increase in the wear resistance of DLC coating under boundary lubrication.
基金This research is supported by TOTAL,Solaize Research Center and Federal Ministry of Economic Affairs and Energy Germany(BMWi)within project CHEOPS3(Funding number 03ET1286B).
文摘To meet the surging needs in energy efficiency and eco-friendly lubricants,a novel superlubricious technology using a vegetable oil and ceramic materials is proposed.By coupling different hydrogen-free amorphous carbon coatings with varying fraction of sp^(2) and sp^(3) hybridized carbon in presence of a commercially available silicon nitride bulk ceramic,castor oil provides superlubricity although the liquid vegetable oil film in the contact is only a few nanometres thick at most.Besides a partial liquid film possibly separating surfaces in contact,local tribochemical reactions between asperities are essential to maintain superlubricity at low speeds.High local pressure activates chemical degradation of castor oil generating graphitic/graphenic-like species on top of asperities,thus helping both the chemical polishing of surface and its chemical passivation by H and OH species.Particularly,the formation of the formation of–(CH_(2)–CH_(2))n–noligomers have been evidenced to have a major role in the friction reduction.Computer simulation unveils that formation of chemical degradation products of castor oil on friction surfaces are favoured by the quantity of sp^(2)-hybridized carbon atoms in the amorphous carbon structure.Hence,tuning sp^(2)-carbon content in hydrogen-free amorphous carbon,in particular,on the top layers of the coating,provides an alternative way to control superlubricity achieved with castor oil and other selected green lubricants.
