High-entropy materials possess high hardness and strong wear resistance,yet the key bottleneck for their practical applications is the poor corrosion resistance in harsh environments.In this work,the high-entropy nitr...High-entropy materials possess high hardness and strong wear resistance,yet the key bottleneck for their practical applications is the poor corrosion resistance in harsh environments.In this work,the high-entropy nitride(HEN)coatings of(MoNbTaTiZr)1-x Nx(x=0-0.47)were fabricated using a hybrid di-rect current magnetron sputtering technique.The research focus was dedicated to the effect of nitrogen content on the microstructure,mechanical and electrochemical properties.The results showed that the as-deposited coatings exhibited a typical body-centered cubic(BCC)structure without nitrogen,while the amorphous matrix with face-centered cubic(FCC)nanocrystalline grain was observed at x=0.17.Further increasing x in the range of 0.35-0.47 caused the appearance of polycrystalline FCC phase in structure.Compared with the MoNbTaTiZr metallic coating,the coating containing nitrogen favored the high hard-ness around 13.7-32.4 GPa,accompanied by excellent tolerance both against elastic and plastic deforma-tion.Furthermore,such N-containing coatings yielded a low corrosion current density of about 10−8-10−7 A/cm^(2) and high electrochemical impedance of 10^(6)Ωcm^(2) in 3.5 wt.%NaCl solution,indicating the supe-rior corrosion resistance.The reason for the enhanced electrochemical behavior could be ascribed to the spontaneous formation of protective passive layers over the coating surface,which consisted of the domi-nated multi-elemental oxides in chemical stability.Particularly,noted that the(MoNbTaTiZr)_(0.83) N0.17 coat-ing displayed the highest hardness of 32.4±2.6 GPa and H/E ratio at 0.09,together with remarkable cor-rosion resistance,proposing the strongest capability for harsh-environmental applications required both good anti-wear and anti-corrosion performance.展开更多
In this study,the tribological behavior and mechanism of multilayered graphite-like carbon(GLC)coatings under different hydrostatic pressures(0.1–60 MPa)were investigated via a simulated deep-sea friction and wear te...In this study,the tribological behavior and mechanism of multilayered graphite-like carbon(GLC)coatings under different hydrostatic pressures(0.1–60 MPa)were investigated via a simulated deep-sea friction and wear test system.The morphology and composition of the friction interface were thoroughly characterized.The findings revealed that the coefficient of friction(COF)was greater(but did not surpass 0.02)under conditions of elevated hydrostatic pressure or heavy load.The GLC coating mainly experiences abrasive wear,and the degree of wear intensifies with increasing hydrostatic pressure and load.The graphitization of the friction interface and the production of silicon-based lubrication products are becoming increasingly evident.Consequently,the effect of hydrostatic pressure on the frictional performance of GLC coatings is achieved by changing the state of the frictional contact surfaces.Essentially,hydrostatic pressure modifies the real contact area of the friction pair by generating additional compressive loads such that an increase in hydrostatic pressure has a similar effect on an increase in the applied load.As the hydrostatic pressure and applied load increase,the trend of abrasion smoothing on the surfaces of the friction pair becomes more pronounced.The graphite transfer film and silicon-based material generated during the friction process improve the lubrication performance of the friction pair,resulting in extremely low wear of the friction pair.展开更多
Due to the excellent corrosion resistance and high irradiation damage resistance,Ti 2AlC MAX phase is considered as a candidate for applications as corrosion resistant and irradiation resistant protective coating.MAX ...Due to the excellent corrosion resistance and high irradiation damage resistance,Ti 2AlC MAX phase is considered as a candidate for applications as corrosion resistant and irradiation resistant protective coating.MAX phase coatings can be fabricated through firstly depositing a coating containing the three elements M,A,and X close to stoichiometry of the MAX phases using physical vapor deposition,followed by heat treatment in vacuum.In this work,Ti-Al-C coating was prepared on austenitic stainless steels by reactive DC magnetron sputtering with a compound Ti （50）Al （50） target,and CH4 used as the reactive gas.It was found that the as-deposited coating is mainly composed of Ti 3AlC antiperovskite phase with supersaturated solid solution of Al.Additionally,the ratio of Ti/Al remained the same as that of the target composition.Nevertheless,a thicker thermally grown Ti 2AlC MAX phase coating was obtained after being annealed at 800℃ in vacuum for 1 h.Meanwhile,the ratio of Ti/Al became close to stoichiometry of Ti 2AlC MAX phases.It can be understood that owing to the higher activity of Al,it diffused quickly into the substrate during annealing,and then more stable Ti 2AlC MAX phases transformed from the Ti 3AlC antiperovskite phase.展开更多
TiN coatings were deposited using a hybrid home-made high power impulse magnetron sputtering(HIPIMS)technique at room temperature.The effects of substrate negative bias voltage on the deposition rate,composition,cryst...TiN coatings were deposited using a hybrid home-made high power impulse magnetron sputtering(HIPIMS)technique at room temperature.The effects of substrate negative bias voltage on the deposition rate,composition,crystal structure,surface morphology,microstructure and mechanical properties were investigated.The results revealed that with the increase in bias voltage from-50 to-400 V,TiN coatings exhibited a trend of densification and the crystal structure gradually evolved from(111) orientation to(200)orientation.The growth rate decreased from about 12.2 nm to 7.8 nm per minute with the coating densification.When the bias voltage was-300 V,the minimum surface roughness value of 10.1 nm was obtained,and the hardness and Young’s modulus of TiN coatings reached the maximum value of 17.4 GPa and 263.8 GPa,respectively.Meanwhile,the highest adhesion of 59 N was obtained between coating and substrate.展开更多
In this paper, graphite-like carbon （GLC） films with Cr buffer layer were fabricated by DC magnetron sputtering technique with the thickness ratio of Cr to GLC films varying from 1：2 to 1：20. The effect of Cr]GLC ...In this paper, graphite-like carbon （GLC） films with Cr buffer layer were fabricated by DC magnetron sputtering technique with the thickness ratio of Cr to GLC films varying from 1：2 to 1：20. The effect of Cr]GLC modulation ratio on microstructure, mechanical and tribological properties in artificial seawater was mainly investigated by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, nano-indenter and a reciprocating sliding tribo-meter. The propagation of defects plays an important role in the evolution of delamination, which is critical to wear failure of GLC films in artificial seawa- ter. Designing the proper multilayer structure could inhibit the defects propagation and thus protect the basis material. The multilayer Cr/GLC film with optimized ratio of 1：3 demonstrates a low average friction coefficient of 0.08 ± 0.006 and wear rate of （2.3 ± 0.3） × 10^-8 mm3/（N m） in artificial seawater, respectively.展开更多
Severe erosion by hard particles is a crucial problem to engine blades when aircraft take off and land in harsh environments, especially for the developed lightweight titanium alloy components. Here, we deposited the ...Severe erosion by hard particles is a crucial problem to engine blades when aircraft take off and land in harsh environments, especially for the developed lightweight titanium alloy components. Here, we deposited the Ti/TiAlN multilayer coatings with various cycles on Ti–6 Al–4 V substrates by a home-made hybrid multisource cathodic arc system. The effects of the silica sand and glass beads on erosion behavior of the coatings were focused. Results showed that the Ti/TiAlN multilayer coatings eroded by the silica sand exhibited the predominant "layer by layer" failure mechanism. In particular, increasing the number of cycles led to the dramatic increase in erosion rate for Ti/TiAlN multilayer coatings, due to the deterioration of their mechanical properties. Different from the silica sand case, however, the erosion rate of the coatings treated by glass beads indicated faint dependence upon the number of cycles, where the coating failure was dominated by the "piece by piece" failure mechanism. Noted that the Ti layers along with the formed interfaces enhanced the erosion resistance of the coatings, although the failure mechanisms were differently eroded by silica sand and glass beads. Meanwhile, the Ti layers and interfaces hindered the propagation of radial cracks and restrained the lateral cracks within one single TiAlN layer.展开更多
The combined micro arc oxidation （MAO） and a hybrid beam deposition process was used to deposit duplex （Si：N）-DLC/MAO coatings on AZ80 magnesium alloy. The microstructure and composition of the duplex coatings we...The combined micro arc oxidation （MAO） and a hybrid beam deposition process was used to deposit duplex （Si：N）-DLC/MAO coatings on AZ80 magnesium alloy. The microstructure and composition of the duplex coatings were analyzed by Raman spectroscopy, X-ray photoelectron spectroscope （XPS）, scanning electron microscope （SEM） and atomic force microscopy （AFM）. Tribological behaviors of the coatings were studied by ball-on-disk friction test. It was found that the ID/IG ratio of the （Si：N）-DLC （diamond-like carbon） top films increases with decreasing C2H2/N2 ratio. The （Si：N）-DLC top film with SigN4 was formed on the MAO coated sample as the C2H2/N2 ratio was 10sccm：5sccm, which showed an increasing critical load compared with the pure DLC directly deposited on the Mg alloy substrate. As a result, the （Si：N）-DLC/MAO coating exhibited an advanced wear protection for the substrate.展开更多
In this work,the high temperature friction mechanism of the tetrahedral amorphous carbon(ta-C)film was elucidated.The multilayer ta-C film with alternating hard and soft sub-layers exhibited a low friction coefficient...In this work,the high temperature friction mechanism of the tetrahedral amorphous carbon(ta-C)film was elucidated.The multilayer ta-C film with alternating hard and soft sub-layers exhibited a low friction coefficient of 0.14 at 400℃ before a sudden failure occurred at 4600 cycles.The wear failure was attributed to the gradual consumption of the ta-C film at the contact region.The design of a hard or soft top layer effectively regulated the high temperature friction properties of the multilayer ta-C.The addition of a hard top layer contributed to a low friction coefficient(0.11)and a minor wear rate(4.0×10^(-7)mm^(3)/(N m)),while a soft top layer deteriorated the lubrication effect.It was proposed that the passivation of dangling bonds at the sliding interface dominated the low-friction mechanism of the ta-C film at high temperature,while the friction induced graphitization and the formation of sp^(2)-rich carbonaceous transfer layer triggered C-C inter-film bonding,resulting in serious adhesion force and lubrication failure.Moreover,the multilayer ta-C film with hard top layer obtained excellent friction performance within 500℃,while the high temperature induced oxidation and volatilization of carbon atoms led to the wear failure at 600℃.展开更多
In this research,the tribocorrosion behavior of 316L stainless steel in simulated seawater was investigated under continuous and intermittent sliding at open circuit potential.The tribocorrosion mechanism was discusse...In this research,the tribocorrosion behavior of 316L stainless steel in simulated seawater was investigated under continuous and intermittent sliding at open circuit potential.The tribocorrosion mechanism was discussed in terms of wear morphologies,mechanical property as well as chemical composition.Meanwhile,microstructure evolution inside the wear track and open circuit potential recorded after sliding were analyzed to quantify the repassivation kinetics and evaluate the impact of the regenerated passive film on wear.The results showed that the wear rate increased under intermittent sliding when the pause time is long enough to repassivate after sliding.Repeated sliding promoted the refinement of the grain inside the sliding area,which was beneficial to the generation of the thicker and more compact passive film inside the wear track.The ruptured passive film often acted as abrasives during subsequent sliding.Therefore,the accelerated material loss under intermittent sliding was attributed to the periodic mechanical removal of the thickened passive film and the enhanced abrasive wear inside the wear track.展开更多
The interesting hybrid properties of ceramics and metals induced by unique nano-laminated structures make the M_(n+1)AX n(MAX)phase attractive as a potential protective coating for vital structural compo-nents in hars...The interesting hybrid properties of ceramics and metals induced by unique nano-laminated structures make the M_(n+1)AX n(MAX)phase attractive as a potential protective coating for vital structural compo-nents in harsh systems.However,an extremely narrow phase-forming region makes it difficult to prepare MAX phase coatings with high purity,which is required to obtain coatings with high-temperature anti-oxidation capabilities.This work describes the dependence of the phase evolution in deposited M-Al-C(M=Ti,V,Cr)coatings as a function on temperature using in-situ X-ray diffraction analysis.Compared to V_(2)AlC and Cr_(2)AlC MAX phase coatings,the Ti_(2)AlC coating displayed a higher phase-forming tempera-ture accompanied by a lack of any intermediate phases before the appearance of the Ti_(2)AlC MAX phase.The results of the first-principle calculations correlated with the experience in which Ti_(2)AlC exhibited the largest formation energy and density of states.The effect of the phase compositions of these three MAX phase coatings on mechanical properties were also investigated using ex-situ Vickers and nano-indenter tests,demonstrating the improved mechanical properties with good stability at high temperatures.These findings provide a deeper understanding of the phase-forming mechanism of MAX phase coatings to guide the preparation of high-purity MAX phase coatings and the optimization of MAX phase coatings with expected intermediate phases such as Cr_(2)C,V_(2)C etc.,as well as their application as protective coat-ings in temperature-related harsh environments.展开更多
Considering the increasing demand for wearresistant materials used for various frictions with dynamic sealing parts,we employed hybrid magnetron sputtering technology to fabricate Cr/amorphous carbon(a-C)multilayered ...Considering the increasing demand for wearresistant materials used for various frictions with dynamic sealing parts,we employed hybrid magnetron sputtering technology to fabricate Cr/amorphous carbon(a-C)multilayered coatings with and without Cr doping for comparison.The tribological behaviors of coatings paired with polyether ether ketone(PEEK)balls were investigated under different friction environments,including an evolving atmosphere,a NaCl solution,polyalphaolefin(PAO)oil,and water-in-oil(W/O).The results demonstrated that the tribological properties of all friction pairs were strongly influenced by the surrounding environment.In the atmosphere and in a NaCl solution,the addition of Cr promoted the formation of a-C-containing transfer films,thereby yielding stable and low friction characteristics.However,the dominant factor contributing to the tribological performance shifted from the coatings themselves to the PAO oil film with PAO medium.In the case of the W/O solution,both the facile reactivity of Cr and the intrinsic instability of the W/O mixture accelerated the presence of Cr_(2)O_(3),which caused more severe wear.The current observations not only identified the tribological failure mechanism of Cr/a-C coatings with and without Cr doping modifications in conjunction with their PEEK counterparts but also addressed the importance of designing and fabricating adaptive lubricant coatings for harsh multi-environment applications.展开更多
Finding water resources is a crucial objective of lunar missions.However,both hydroxyl(OH)and natural water(H2O)have been reported to be scarce on the Moon.We propose a potential method for obtaining water on the Moon...Finding water resources is a crucial objective of lunar missions.However,both hydroxyl(OH)and natural water(H2O)have been reported to be scarce on the Moon.We propose a potential method for obtaining water on the Moon through H2O formation via endogenous reactions in lunar regolith(LR),specifically through the reaction FeO/Fe2O3+H/Fe+H2O.This process is demonstrated using LR samples brought back by the Chang’E-5 mission.FeO and Fe2O3 are lunar minerals containing Fe oxides.Hydrogen(H)retained in lunar minerals from the solar wind can be used to produce water.The results of this study reveal that 51–76 mg of H2O can be generated from 1 g of LR after melting at temperatures above 1,200 K.This amount is10,000 times the naturally occurring OH and H2O on the Moon.Among the five primary minerals in LR returned by the Chang’E-5 mission,FeTiO3 ilmenite contains the highest amount of H,owing to its unique lattice structure with sub-nanometer tunnels.For the first time,in situ heating experiments using a transmission electron microscope reveal the concurrent formation of Fe crystals and H2O bubbles.Electron irradiation promotes the endogenous redox reaction,which is helpful for understanding the distribution of OH on the Moon.Our findings suggest that the hydrogen retained in LR is a significant resource for obtaining H2O on the Moon,which is helpful for establishing a scientific research station on the Moon.展开更多
Surface-modified Zr-based alloy(ZIRLO)claddings with advanced ceramic coatings are increasingly required for accident-tolerant fuel(ATF)systems in light-water reactors.Cr_(2)AlC MAX phase coatings are promising for th...Surface-modified Zr-based alloy(ZIRLO)claddings with advanced ceramic coatings are increasingly required for accident-tolerant fuel(ATF)systems in light-water reactors.Cr_(2)AlC MAX phase coatings are promising for this purpose owing to their remarkable properties combining radiation/oxidation/corrosion resistance.However they are suffering from weak interface compatibility to ZIRLO substrate and poor structural densities for long-term services.Herein,we fabricated densely high-purity Cr_(2)AlC MAX phase coatings with uniquely designed Cr/CrC_(x)interfacial layers.The oxidation behavior of the coatings was focused under steam environments at 1000–1200℃.Results showed that Cr_(2)AlC coatings exhibited an oxidation mass gain of 8.9 mg/cm^(2)and an oxide thickness of 680 nm after oxidation at 1200℃ for 30 min,which were about 10%and 0.5%of ZIRLO substrate,respectively.Based on microstructural evolutions,the embedded interfacial layers significantly suppressed the rapid diffusion of Al in Cr_(2)AlC coatings to the substrate and the premature delamination of oxidized coatings.Particularly,the formed oxides were identified as dense yet pure α-Al_(2)O_(3),which endowed the protection against further oxidation and excellent resistance to high-temperature steam corrosion.展开更多
The Cr-coated Zr alloys demonstrate excellent resistance to high-temperature steam oxidation.However,the rapid diffusion pathways for oxygen formed by the inter-diffusion between the coating and alloy at high temperat...The Cr-coated Zr alloys demonstrate excellent resistance to high-temperature steam oxidation.However,the rapid diffusion pathways for oxygen formed by the inter-diffusion between the coating and alloy at high temperatures significantly affect the steam oxidation resistance of the coated alloys.To address this issue,we developed a Mo/Cr bilayer coating on Zr alloy by a combination of dc-MS and HiPIMS surface treatments.The coating exhibits outstanding steam oxidation resistance at high temperatures,resulting in a mass gain approximately 86.6%and 44.1%lower than that of the bare Zr alloy and Cr coating,respectively,after 30 min of steam oxidation at 1200℃.This is mainly because,during the oxidation process,the Mo interface layer undergoes a transformation into a thin and high-quality double diffusion layer structure,effectively avoiding high-temperature inter-diffusion between the Cr coating and Zr alloy,thereby inhibiting the formation of oxygen diffusion pathways.展开更多
Solid lubricating coatings play a crucial role in preventing friction and wear failure of the hot-end sliding components in aviation engines.In this study,VAlN/Ag multi-layer coatings with excellent interfacial matchi...Solid lubricating coatings play a crucial role in preventing friction and wear failure of the hot-end sliding components in aviation engines.In this study,VAlN/Ag multi-layer coatings with excellent interfacial matching were fabricated using a hybrid magnetron sputtering technique.The type and energy of discharge plasmas were analyzed to comprehend their effects on depositing coatings.The coatings exhibit self-adaptive lubrication properties during the designed consecutive friction with stepwise heating from 25℃to 650℃.The microstructure evolution during early friction facilitates sufficient tribo-chemical reaction at 650℃,leading to the formation of a distinctive"ball-on-rail"structure that significantly reduces friction coefficient.Based on the first-principles calculations,it was found that the bond energy of Ag-O is lower than that of V-O in both AgVO_(3)and Ag_(3)VO_(4),which promotes slipping along the(110)crystal plane and contributes to exceptional tribological properties.The fatigue wear failure mechanism of hard coatings under the thermal-force coupling effects has been elucidated,alongside an exploration of consecutive tribology mechanism at atomic scales over a wide temperature range.展开更多
Current tribocorrosion research of metallic materials and their surface protective coatings mainly focuses on their short-term properties,with test time of 0.5‒2.0 h and a sliding distance 50‒500 m,which may significa...Current tribocorrosion research of metallic materials and their surface protective coatings mainly focuses on their short-term properties,with test time of 0.5‒2.0 h and a sliding distance 50‒500 m,which may significantly deviate from the practical long-term service condition and thus cause a catastrophe of marine equipments.In this study,three carbon-based multilayer coatings(Ti/DLC,TiC_(x)/DLC,and Ti‒TiC_(x)/DLC)were deposited on S32750 substrates,and both short-term and long-term tribocorrosion behaviors were investigated.The experimental results indicate that the coatings substantially improve the tribocorrosion resistance of the S32750 stainless steel.During the short-term tribocorrosion test,TiC_(x)/DLC exhibited the best tribocorrosion resistance owing to its high hardness.During the long-term tribocorrosion test,however,Ti‒TiC_(x)/DLC coating indicated the best anti-tribocorrosion performance owing to its excellent fracture toughness together with high hardness.Moreover,under 5 N,Ti‒TiC_(x)/DLC can withstand a long-term test of more than 24 h.Additionally,under a higher load of 20 N,the Ti‒TiC_(x)/DLC with a corresponding sliding distance of approximately 1,728 m maintained a low friction coefficient of approximately 0.06.However,the coating was completely worn out;this is attributable to the formation of tribocorrosion products consisting of graphitized carbon and nanocrystalline Fe_(x)O_(y).展开更多
基金supported by the National Science Fund for Distinguished Young Scholars of China(No.52025014)Zhejiang Provincial Natural Science Foundation of China(Nos.LZJWY23E090001 and LD24E010003)the Natural Science Foundation of Ningbo(No.2022J305).
文摘High-entropy materials possess high hardness and strong wear resistance,yet the key bottleneck for their practical applications is the poor corrosion resistance in harsh environments.In this work,the high-entropy nitride(HEN)coatings of(MoNbTaTiZr)1-x Nx(x=0-0.47)were fabricated using a hybrid di-rect current magnetron sputtering technique.The research focus was dedicated to the effect of nitrogen content on the microstructure,mechanical and electrochemical properties.The results showed that the as-deposited coatings exhibited a typical body-centered cubic(BCC)structure without nitrogen,while the amorphous matrix with face-centered cubic(FCC)nanocrystalline grain was observed at x=0.17.Further increasing x in the range of 0.35-0.47 caused the appearance of polycrystalline FCC phase in structure.Compared with the MoNbTaTiZr metallic coating,the coating containing nitrogen favored the high hard-ness around 13.7-32.4 GPa,accompanied by excellent tolerance both against elastic and plastic deforma-tion.Furthermore,such N-containing coatings yielded a low corrosion current density of about 10−8-10−7 A/cm^(2) and high electrochemical impedance of 10^(6)Ωcm^(2) in 3.5 wt.%NaCl solution,indicating the supe-rior corrosion resistance.The reason for the enhanced electrochemical behavior could be ascribed to the spontaneous formation of protective passive layers over the coating surface,which consisted of the domi-nated multi-elemental oxides in chemical stability.Particularly,noted that the(MoNbTaTiZr)_(0.83) N0.17 coat-ing displayed the highest hardness of 32.4±2.6 GPa and H/E ratio at 0.09,together with remarkable cor-rosion resistance,proposing the strongest capability for harsh-environmental applications required both good anti-wear and anti-corrosion performance.
基金financially supported by the National Key R&D Program of China(No.2022YFC2805701)the National Science Fund for Distinguished Young Scholars of China(No.52025014),the National Natural Science Foundation of China(No.52127803)the Ningbo Science and Technology Innovation Project(No.2023Z198).
文摘In this study,the tribological behavior and mechanism of multilayered graphite-like carbon(GLC)coatings under different hydrostatic pressures(0.1–60 MPa)were investigated via a simulated deep-sea friction and wear test system.The morphology and composition of the friction interface were thoroughly characterized.The findings revealed that the coefficient of friction(COF)was greater(but did not surpass 0.02)under conditions of elevated hydrostatic pressure or heavy load.The GLC coating mainly experiences abrasive wear,and the degree of wear intensifies with increasing hydrostatic pressure and load.The graphitization of the friction interface and the production of silicon-based lubrication products are becoming increasingly evident.Consequently,the effect of hydrostatic pressure on the frictional performance of GLC coatings is achieved by changing the state of the frictional contact surfaces.Essentially,hydrostatic pressure modifies the real contact area of the friction pair by generating additional compressive loads such that an increase in hydrostatic pressure has a similar effect on an increase in the applied load.As the hydrostatic pressure and applied load increase,the trend of abrasion smoothing on the surfaces of the friction pair becomes more pronounced.The graphite transfer film and silicon-based material generated during the friction process improve the lubrication performance of the friction pair,resulting in extremely low wear of the friction pair.
基金supported by the National Natural Science Foundation of China (Grant No.51522106 and Grant No.51401229)the National Science and Technology Major Project of China (Grant No.2015ZX06004-001)the Ningbo Municipal Natural Science Foundation (Grant No.2014A610013)
文摘Due to the excellent corrosion resistance and high irradiation damage resistance,Ti 2AlC MAX phase is considered as a candidate for applications as corrosion resistant and irradiation resistant protective coating.MAX phase coatings can be fabricated through firstly depositing a coating containing the three elements M,A,and X close to stoichiometry of the MAX phases using physical vapor deposition,followed by heat treatment in vacuum.In this work,Ti-Al-C coating was prepared on austenitic stainless steels by reactive DC magnetron sputtering with a compound Ti （50）Al （50） target,and CH4 used as the reactive gas.It was found that the as-deposited coating is mainly composed of Ti 3AlC antiperovskite phase with supersaturated solid solution of Al.Additionally,the ratio of Ti/Al remained the same as that of the target composition.Nevertheless,a thicker thermally grown Ti 2AlC MAX phase coating was obtained after being annealed at 800℃ in vacuum for 1 h.Meanwhile,the ratio of Ti/Al became close to stoichiometry of Ti 2AlC MAX phases.It can be understood that owing to the higher activity of Al,it diffused quickly into the substrate during annealing,and then more stable Ti 2AlC MAX phases transformed from the Ti 3AlC antiperovskite phase.
基金financially supported by the program of National Natural Science Foundation of China (Grant No. 51375475)the Instrument Developing Project of the Chinese Academy of Sciences (Grant No. YZ201326)
文摘TiN coatings were deposited using a hybrid home-made high power impulse magnetron sputtering(HIPIMS)technique at room temperature.The effects of substrate negative bias voltage on the deposition rate,composition,crystal structure,surface morphology,microstructure and mechanical properties were investigated.The results revealed that with the increase in bias voltage from-50 to-400 V,TiN coatings exhibited a trend of densification and the crystal structure gradually evolved from(111) orientation to(200)orientation.The growth rate decreased from about 12.2 nm to 7.8 nm per minute with the coating densification.When the bias voltage was-300 V,the minimum surface roughness value of 10.1 nm was obtained,and the hardness and Young’s modulus of TiN coatings reached the maximum value of 17.4 GPa and 263.8 GPa,respectively.Meanwhile,the highest adhesion of 59 N was obtained between coating and substrate.
基金supported by the National Natural Science Foundation of China(Nos.51522106 and 51375475)Zhejiang Key Research and Development Program(2017C01001)Public Projects of Zhejiang Province
文摘In this paper, graphite-like carbon （GLC） films with Cr buffer layer were fabricated by DC magnetron sputtering technique with the thickness ratio of Cr to GLC films varying from 1：2 to 1：20. The effect of Cr]GLC modulation ratio on microstructure, mechanical and tribological properties in artificial seawater was mainly investigated by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, nano-indenter and a reciprocating sliding tribo-meter. The propagation of defects plays an important role in the evolution of delamination, which is critical to wear failure of GLC films in artificial seawa- ter. Designing the proper multilayer structure could inhibit the defects propagation and thus protect the basis material. The multilayer Cr/GLC film with optimized ratio of 1：3 demonstrates a low average friction coefficient of 0.08 ± 0.006 and wear rate of （2.3 ± 0.3） × 10^-8 mm3/（N m） in artificial seawater, respectively.
基金financially supported by the National Science and Technology Major Project(No.2017-VII-0012-0108)CAS Interdisciplinary Innovation Team(No.292020000008)K.C.Wong Education Foundation(No.GJTD-2019-13)。
文摘Severe erosion by hard particles is a crucial problem to engine blades when aircraft take off and land in harsh environments, especially for the developed lightweight titanium alloy components. Here, we deposited the Ti/TiAlN multilayer coatings with various cycles on Ti–6 Al–4 V substrates by a home-made hybrid multisource cathodic arc system. The effects of the silica sand and glass beads on erosion behavior of the coatings were focused. Results showed that the Ti/TiAlN multilayer coatings eroded by the silica sand exhibited the predominant "layer by layer" failure mechanism. In particular, increasing the number of cycles led to the dramatic increase in erosion rate for Ti/TiAlN multilayer coatings, due to the deterioration of their mechanical properties. Different from the silica sand case, however, the erosion rate of the coatings treated by glass beads indicated faint dependence upon the number of cycles, where the coating failure was dominated by the "piece by piece" failure mechanism. Noted that the Ti layers along with the formed interfaces enhanced the erosion resistance of the coatings, although the failure mechanisms were differently eroded by silica sand and glass beads. Meanwhile, the Ti layers and interfaces hindered the propagation of radial cracks and restrained the lateral cracks within one single TiAlN layer.
基金the financial support of the National Natural Science Foundation of China(Grant No.51201176)Industrialization Project of Education Department of Shaanxi Province(GrantNo.2012JC13)Zhejiang Provincial Natural Science Foundation of China(Grant No.Y2110401)
文摘The combined micro arc oxidation （MAO） and a hybrid beam deposition process was used to deposit duplex （Si：N）-DLC/MAO coatings on AZ80 magnesium alloy. The microstructure and composition of the duplex coatings were analyzed by Raman spectroscopy, X-ray photoelectron spectroscope （XPS）, scanning electron microscope （SEM） and atomic force microscopy （AFM）. Tribological behaviors of the coatings were studied by ball-on-disk friction test. It was found that the ID/IG ratio of the （Si：N）-DLC （diamond-like carbon） top films increases with decreasing C2H2/N2 ratio. The （Si：N）-DLC top film with SigN4 was formed on the MAO coated sample as the C2H2/N2 ratio was 10sccm：5sccm, which showed an increasing critical load compared with the pure DLC directly deposited on the Mg alloy substrate. As a result, the （Si：N）-DLC/MAO coating exhibited an advanced wear protection for the substrate.
基金funded by The National Science Fund for Distinguished Young Scholars of China(No.52025014)National Science and Technology Major Project(No.2017-VII-0012-0108)+2 种基金K.C.Wong Education Foundation(No.GJTD-2019-13)CAS Interdisciplinary Innovation Team(No.292020000008)Ningbo Science and Technology Innovation Project(No.2018B10012)。
文摘In this work,the high temperature friction mechanism of the tetrahedral amorphous carbon(ta-C)film was elucidated.The multilayer ta-C film with alternating hard and soft sub-layers exhibited a low friction coefficient of 0.14 at 400℃ before a sudden failure occurred at 4600 cycles.The wear failure was attributed to the gradual consumption of the ta-C film at the contact region.The design of a hard or soft top layer effectively regulated the high temperature friction properties of the multilayer ta-C.The addition of a hard top layer contributed to a low friction coefficient(0.11)and a minor wear rate(4.0×10^(-7)mm^(3)/(N m)),while a soft top layer deteriorated the lubrication effect.It was proposed that the passivation of dangling bonds at the sliding interface dominated the low-friction mechanism of the ta-C film at high temperature,while the friction induced graphitization and the formation of sp^(2)-rich carbonaceous transfer layer triggered C-C inter-film bonding,resulting in serious adhesion force and lubrication failure.Moreover,the multilayer ta-C film with hard top layer obtained excellent friction performance within 500℃,while the high temperature induced oxidation and volatilization of carbon atoms led to the wear failure at 600℃.
基金A-class pilot of the Chinese Academy of Sciences(No.XDA22010303)National Science Fund for Distinguished Young Scholars of China(No.52025014)+3 种基金CAS Interdisciplinary Innovation Team(No.292020000008)CASNST Joint Research Project(No.174433KYSB20200021)National Natural Science Foundation of China(No.51801226)K.C.Wong Education Foundation(No.GJTD-2019–13)。
文摘In this research,the tribocorrosion behavior of 316L stainless steel in simulated seawater was investigated under continuous and intermittent sliding at open circuit potential.The tribocorrosion mechanism was discussed in terms of wear morphologies,mechanical property as well as chemical composition.Meanwhile,microstructure evolution inside the wear track and open circuit potential recorded after sliding were analyzed to quantify the repassivation kinetics and evaluate the impact of the regenerated passive film on wear.The results showed that the wear rate increased under intermittent sliding when the pause time is long enough to repassivate after sliding.Repeated sliding promoted the refinement of the grain inside the sliding area,which was beneficial to the generation of the thicker and more compact passive film inside the wear track.The ruptured passive film often acted as abrasives during subsequent sliding.Therefore,the accelerated material loss under intermittent sliding was attributed to the periodic mechanical removal of the thickened passive film and the enhanced abrasive wear inside the wear track.
基金financially supported by the National Natural Science Foundation of China (Nos.52025014,52171090,52101109,U22A20111).
文摘The interesting hybrid properties of ceramics and metals induced by unique nano-laminated structures make the M_(n+1)AX n(MAX)phase attractive as a potential protective coating for vital structural compo-nents in harsh systems.However,an extremely narrow phase-forming region makes it difficult to prepare MAX phase coatings with high purity,which is required to obtain coatings with high-temperature anti-oxidation capabilities.This work describes the dependence of the phase evolution in deposited M-Al-C(M=Ti,V,Cr)coatings as a function on temperature using in-situ X-ray diffraction analysis.Compared to V_(2)AlC and Cr_(2)AlC MAX phase coatings,the Ti_(2)AlC coating displayed a higher phase-forming tempera-ture accompanied by a lack of any intermediate phases before the appearance of the Ti_(2)AlC MAX phase.The results of the first-principle calculations correlated with the experience in which Ti_(2)AlC exhibited the largest formation energy and density of states.The effect of the phase compositions of these three MAX phase coatings on mechanical properties were also investigated using ex-situ Vickers and nano-indenter tests,demonstrating the improved mechanical properties with good stability at high temperatures.These findings provide a deeper understanding of the phase-forming mechanism of MAX phase coatings to guide the preparation of high-purity MAX phase coatings and the optimization of MAX phase coatings with expected intermediate phases such as Cr_(2)C,V_(2)C etc.,as well as their application as protective coat-ings in temperature-related harsh environments.
基金financially supported by the National Key R&D Program of China(2022YFC2805701)the National Natural Science Foundation of China(52025014 and U20A20296)+1 种基金Zhejiang Lingyan Research and Development Program(2024C01159)Major Special Project of Ningbo(2023Z198).
文摘Considering the increasing demand for wearresistant materials used for various frictions with dynamic sealing parts,we employed hybrid magnetron sputtering technology to fabricate Cr/amorphous carbon(a-C)multilayered coatings with and without Cr doping for comparison.The tribological behaviors of coatings paired with polyether ether ketone(PEEK)balls were investigated under different friction environments,including an evolving atmosphere,a NaCl solution,polyalphaolefin(PAO)oil,and water-in-oil(W/O).The results demonstrated that the tribological properties of all friction pairs were strongly influenced by the surrounding environment.In the atmosphere and in a NaCl solution,the addition of Cr promoted the formation of a-C-containing transfer films,thereby yielding stable and low friction characteristics.However,the dominant factor contributing to the tribological performance shifted from the coatings themselves to the PAO oil film with PAO medium.In the case of the W/O solution,both the facile reactivity of Cr and the intrinsic instability of the W/O mixture accelerated the presence of Cr_(2)O_(3),which caused more severe wear.The current observations not only identified the tribological failure mechanism of Cr/a-C coatings with and without Cr doping modifications in conjunction with their PEEK counterparts but also addressed the importance of designing and fabricating adaptive lubricant coatings for harsh multi-environment applications.
基金Financial support from the National Key R&D Program of China(2018YFA0703600)the National Natural Science Foundation of China(NSFC 52222105,51922102,92163108,61888102,and 51827801)+2 种基金the Youth Innovation Promotion Association CAS(2019296)the Zhejiang Provincial Natural Science Foundation of China(LZ22A030001 and LR22E010004)the Ningbo 2025 Science and Technology Innovation Project is acknowledged.
文摘Finding water resources is a crucial objective of lunar missions.However,both hydroxyl(OH)and natural water(H2O)have been reported to be scarce on the Moon.We propose a potential method for obtaining water on the Moon through H2O formation via endogenous reactions in lunar regolith(LR),specifically through the reaction FeO/Fe2O3+H/Fe+H2O.This process is demonstrated using LR samples brought back by the Chang’E-5 mission.FeO and Fe2O3 are lunar minerals containing Fe oxides.Hydrogen(H)retained in lunar minerals from the solar wind can be used to produce water.The results of this study reveal that 51–76 mg of H2O can be generated from 1 g of LR after melting at temperatures above 1,200 K.This amount is10,000 times the naturally occurring OH and H2O on the Moon.Among the five primary minerals in LR returned by the Chang’E-5 mission,FeTiO3 ilmenite contains the highest amount of H,owing to its unique lattice structure with sub-nanometer tunnels.For the first time,in situ heating experiments using a transmission electron microscope reveal the concurrent formation of Fe crystals and H2O bubbles.Electron irradiation promotes the endogenous redox reaction,which is helpful for understanding the distribution of OH on the Moon.Our findings suggest that the hydrogen retained in LR is a significant resource for obtaining H2O on the Moon,which is helpful for establishing a scientific research station on the Moon.
基金financially supported by the National Natural Science Foundation of China(52171090,U22A20111)the National Science Fund for Distinguished Young Scholars of China(52025014)the Municipal Natural Science Foundation of Ningbo(2023J410,2022J305)
文摘Surface-modified Zr-based alloy(ZIRLO)claddings with advanced ceramic coatings are increasingly required for accident-tolerant fuel(ATF)systems in light-water reactors.Cr_(2)AlC MAX phase coatings are promising for this purpose owing to their remarkable properties combining radiation/oxidation/corrosion resistance.However they are suffering from weak interface compatibility to ZIRLO substrate and poor structural densities for long-term services.Herein,we fabricated densely high-purity Cr_(2)AlC MAX phase coatings with uniquely designed Cr/CrC_(x)interfacial layers.The oxidation behavior of the coatings was focused under steam environments at 1000–1200℃.Results showed that Cr_(2)AlC coatings exhibited an oxidation mass gain of 8.9 mg/cm^(2)and an oxide thickness of 680 nm after oxidation at 1200℃ for 30 min,which were about 10%and 0.5%of ZIRLO substrate,respectively.Based on microstructural evolutions,the embedded interfacial layers significantly suppressed the rapid diffusion of Al in Cr_(2)AlC coatings to the substrate and the premature delamination of oxidized coatings.Particularly,the formed oxides were identified as dense yet pure α-Al_(2)O_(3),which endowed the protection against further oxidation and excellent resistance to high-temperature steam corrosion.
基金financially supported by the National Natural Science Foundation of China(U22A20111)the Key Research and Development Program of Ningbo(20232ZDYF020062)
文摘The Cr-coated Zr alloys demonstrate excellent resistance to high-temperature steam oxidation.However,the rapid diffusion pathways for oxygen formed by the inter-diffusion between the coating and alloy at high temperatures significantly affect the steam oxidation resistance of the coated alloys.To address this issue,we developed a Mo/Cr bilayer coating on Zr alloy by a combination of dc-MS and HiPIMS surface treatments.The coating exhibits outstanding steam oxidation resistance at high temperatures,resulting in a mass gain approximately 86.6%and 44.1%lower than that of the bare Zr alloy and Cr coating,respectively,after 30 min of steam oxidation at 1200℃.This is mainly because,during the oxidation process,the Mo interface layer undergoes a transformation into a thin and high-quality double diffusion layer structure,effectively avoiding high-temperature inter-diffusion between the Cr coating and Zr alloy,thereby inhibiting the formation of oxygen diffusion pathways.
基金supported by the National Natural Science Foundation of China(No.52025014)Natural Science Foundation of Zhejiang Province(No.LQ23E010002)+1 种基金Natural Science Foundation of Ningbo(No.2023QL049)Major Special Project of Ningbo(No.2023Z022).
文摘Solid lubricating coatings play a crucial role in preventing friction and wear failure of the hot-end sliding components in aviation engines.In this study,VAlN/Ag multi-layer coatings with excellent interfacial matching were fabricated using a hybrid magnetron sputtering technique.The type and energy of discharge plasmas were analyzed to comprehend their effects on depositing coatings.The coatings exhibit self-adaptive lubrication properties during the designed consecutive friction with stepwise heating from 25℃to 650℃.The microstructure evolution during early friction facilitates sufficient tribo-chemical reaction at 650℃,leading to the formation of a distinctive"ball-on-rail"structure that significantly reduces friction coefficient.Based on the first-principles calculations,it was found that the bond energy of Ag-O is lower than that of V-O in both AgVO_(3)and Ag_(3)VO_(4),which promotes slipping along the(110)crystal plane and contributes to exceptional tribological properties.The fatigue wear failure mechanism of hard coatings under the thermal-force coupling effects has been elucidated,alongside an exploration of consecutive tribology mechanism at atomic scales over a wide temperature range.
基金This work was supported by the National Natural Science Foundation of China(Nos.52025014 and 51801226)A-class pilot of the Chinese Academy of Sciences(No.XDA22010303)+2 种基金K.C.Wong Education Foundation(No.GJTD-2019-13)CAS-NST Joint Research Project(No.174433KYSB20200021)CAS Interdisciplinary Innovation Team(No.292020000008).
文摘Current tribocorrosion research of metallic materials and their surface protective coatings mainly focuses on their short-term properties,with test time of 0.5‒2.0 h and a sliding distance 50‒500 m,which may significantly deviate from the practical long-term service condition and thus cause a catastrophe of marine equipments.In this study,three carbon-based multilayer coatings(Ti/DLC,TiC_(x)/DLC,and Ti‒TiC_(x)/DLC)were deposited on S32750 substrates,and both short-term and long-term tribocorrosion behaviors were investigated.The experimental results indicate that the coatings substantially improve the tribocorrosion resistance of the S32750 stainless steel.During the short-term tribocorrosion test,TiC_(x)/DLC exhibited the best tribocorrosion resistance owing to its high hardness.During the long-term tribocorrosion test,however,Ti‒TiC_(x)/DLC coating indicated the best anti-tribocorrosion performance owing to its excellent fracture toughness together with high hardness.Moreover,under 5 N,Ti‒TiC_(x)/DLC can withstand a long-term test of more than 24 h.Additionally,under a higher load of 20 N,the Ti‒TiC_(x)/DLC with a corresponding sliding distance of approximately 1,728 m maintained a low friction coefficient of approximately 0.06.However,the coating was completely worn out;this is attributable to the formation of tribocorrosion products consisting of graphitized carbon and nanocrystalline Fe_(x)O_(y).
