Air plasma sprayed thermal barrier coatings(APS-TBCs)saw their wide application in high-temperaturerelated cutting-edge fields.The lamellar structure of APS-TBCs provides a significant advantage on thermal insulation....Air plasma sprayed thermal barrier coatings(APS-TBCs)saw their wide application in high-temperaturerelated cutting-edge fields.The lamellar structure of APS-TBCs provides a significant advantage on thermal insulation.However,short life span is a major headache for APS-TBCs.This is highly related to the property changes and passive behaviors of the coatings during thermal service.Herein,a finite element model was developed to investigate the dynamic stiffening and substrate constraint on total spallation process.Results show that the stiffening accelerates the crack propagation of APS-TBCs.The driving force for crack propagation,which is characterized by strain energy release rate(SERR),is significantly enlarged.Consequently,the crack starts to propagate when the SERR exceeds the fracture toughness.In addition,the changing trends of SERR and crack propagation features are highly associated with temperatures.A higher temperature corresponds to more significant effect of stiffening on substrate constraint.In brief,temperature-dependent stiffening significantly aggravates the substrate constraint effect on APS-TBCs,which is one of the major causes for the spallation.Given that,lowering stiffening degree is essential to maintain high strain tolerance,and to further extend the life span of APS-TBCs.This understanding contributes to the development of advanced TBCs in future applications.展开更多
Laser etching and laser chemical vapor deposition(LCVD)techniques were proposed for the rapid preparation of high-purity,strongly bonded SiC porous micro-nano-coatings on quartz substrates.The laser serves as an exter...Laser etching and laser chemical vapor deposition(LCVD)techniques were proposed for the rapid preparation of high-purity,strongly bonded SiC porous micro-nano-coatings on quartz substrates.The laser serves as an external driving force for the vertical growth of SiC whiskers,facilitating the formation of a porous nanostructure that resembles coral models found in the macroscopic biological world.The porous nanostructures are beneficial for reducing thermal expansion mismatch and relieving residual stress.It is capable of eliminating the cracks on the surface of SiC coatings as well as enhancing the bonding of SiC coatings with quartz substrates to avoid coating detachment.展开更多
Developing high-efficient flame-retardant coatings is crucial for fire safety polymer and battery fields.Traditional intumescent coatings and ceramifiable coatings struggle to provide immediate and prolonged protectio...Developing high-efficient flame-retardant coatings is crucial for fire safety polymer and battery fields.Traditional intumescent coatings and ceramifiable coatings struggle to provide immediate and prolonged protection simultaneously,which limits the applicability.To address this,an innovative bi-layered coating with organic/nano-inorganic additives is inspired by differential response behaviors,enabling relay response effect with both fast-acting and extended protection.Specifically,two layers function continuously in the form of a relay.With a mere 320 microns,the bi-layered coating withstands fire temperatures of up to 1400℃for at least 900 s.Consequently,the coating effective prevented burn through in aluminum plates and glass fabric-reinforced epoxy resin,which otherwise were burned through in 135 and 173 s,respectively.Meanwhile,the bi-layered coating suppressed the formation and decomposition of solid interface layer in lithium soft-package batteries,leading to prolonged electrochemical stability and fire safety.Additionally,the bi-layered coating with a fast response endows polyurethane foam with rapid self-extinguishing,preventing ignition even under exposure to strong fire of 1400℃.Shortly,our work offers new insights into the design and development of thin,high-performance,and multi-application flame-retardant coatings.展开更多
Fe-based coating was produced on pure Ti substrate by the laser cladding technology. The composition and microstructure of the fabricated coating were analyzed by scanning electron microscopy （SEM）, X-ray diffracti...Fe-based coating was produced on pure Ti substrate by the laser cladding technology. The composition and microstructure of the fabricated coating were analyzed by scanning electron microscopy （SEM）, X-ray diffraction （XRD） and transmission electron microscopy （TEM） technique. The tribological properties were tested through sliding against AISI52100 steel ball at different normal loads and sliding speeds. Besides, the morphologies of the worn surfaces and wear debris were analyzed by scanning electron microscopy （SEM） and three dimensional （3D） non-contact surface mapping. The results show that the prepared Fe-based coating has a high hardness of about 860 HV0.2 and exhibits an average wear rate of （0.70-2.32）×10-6 mm3/（N-m）, showing that the Fe-based coating can greatly improve the wear resistance of pure Ti substrate. The wear mechanism of the coating involves moderate adhesive and abrasive wear.展开更多
The outermost coating with single phase Ni2Al3 was obtained on copper surface by electrodepositing nickel followed by slurry pack aluminizing at 800 °C for 12 h. The oxidation resistance and microstructure of the...The outermost coating with single phase Ni2Al3 was obtained on copper surface by electrodepositing nickel followed by slurry pack aluminizing at 800 °C for 12 h. The oxidation resistance and microstructure of the coating oxidized in ambient air at 1000 °C for 25-250 h were investigated using SEM, X-ray diffraction and optical microscope methods. The results show that the copper with single phase Ni2Al3 coating possesses the best high temperature oxidation resistance, and the mass gain of the coating is 1/15 that of pure copper and 1/2 that of nickel coating, respectively. The specimen surface after being oxidized for 25 h still comprises Ni2Al3 phase. However, when the time of oxidizing treatment increases to 50 h, the Ni Al phase is formed. It is also found that the Ni2Al3 phase completely turns into Ni Al phase after oxidizing treatment for 100 h and above. The Ni Al coating shows excellent high temperature oxidation resistance when oxidation time is 250 h.展开更多
The propagation characteristics of laser-generated like-Rayleigh waves in viscoelastic adhesive coating/substrate structures were studied.Considering the viscoelasticity of the coating and substrate,we have establishe...The propagation characteristics of laser-generated like-Rayleigh waves in viscoelastic adhesive coating/substrate structures were studied.Considering the viscoelasticity of the coating and substrate,we have established the finite element models in frequency domain for the laser-generated like-Rayleigh waves in the epoxy coating/aluminum substrate,epoxy coating/brass substrate,and epoxy coating/foam substrate structures,respectively.In addition,we have investigated the waveform and propagation characteristics of the like-Rayleigh waves and studied the influences of the coating transparency,coating thickness,coating viscoelasticity,and substrate viscoelasticity on the propagation characteristics of the like-Rayleigh waves.Moreover,we have verified the results by the theoretical phase velocity and attenuation curves.The results show that the coating viscoelasticity induces the attenuation characteristics of the higher frequencies of the like-Rayleigh waves,but has little effect on the lower frequencies,and the substrate viscoelasticity has the influences on both the higher and lower frequencies of the like-Rayleigh waves,especially the lower frequencies.Furthermore,the mode and dispersive characteristics of the like-Rayleigh waves are closely related to the substrates.This study provides a useful theoretical basis for inverting mechanical parameters and evaluating the adhesive quality of the viscoelastic adhesive coating/substrate structures.展开更多
Ti/TiN/Zr/ZrN multilayer coatings were deposited on Cr_17Ni_2 steel substrates with different surface roughnesses by vacuum cathodic arc deposition method. Microstructure, micro-hardness, adhesion strength and cross-s...Ti/TiN/Zr/ZrN multilayer coatings were deposited on Cr_17Ni_2 steel substrates with different surface roughnesses by vacuum cathodic arc deposition method. Microstructure, micro-hardness, adhesion strength and cross-sectional morphology of the obtained multilayer coatings were investigated. The results show that the Vickers hardness of Ti/TiN/Zr/ZrN multilayer coating, with a film thickness of 11.37 μm, is 29.36 GPa. The erosion and salt spray resistance performance of Cr_17Ni_2 steel substrates can be evidently improved by Ti/TiN/Zr/ZrN multilayer coating. The surface roughness of Cr_17Ni_2 steel substrates plays an important role in determining the mechanical and erosion performances of Ti/TiN/Zr/ZrN multilayer coatings. Overall, a low value of the surface roughness of substrates corresponds to an improved performance of erosion and salt spray resistance of multilayer coatings. The optimized performance of Ti/TiN/Zr/ZrN multilayer coatings can be achieved provided that the surface roughness of Cr_17Ni_2 steel substrates is lower than 0.4μm.展开更多
This paper investigates the functionally graded coating bonded to an elastic strip with a crack under thermal- mechanical loading. Considering some new boundary conditions, it is assumed that the temperature drop acro...This paper investigates the functionally graded coating bonded to an elastic strip with a crack under thermal- mechanical loading. Considering some new boundary conditions, it is assumed that the temperature drop across the crack surface is the result of the thermal conductivity index which controls heat conduction through the crack region. By the Fourier transforms, the thermal-elastic mixed boundary value problems are reduced to a system of singular integral equations which can be approximately solved by applying the Chebyshev polynomials. The numerical computation methods for the temperature, the displacement field and the thermal stress intensity factors （TSIFs） are presented. The normal temperature distributions （NTD） with different parameters along the crack surface are analyzed by numerical examples. The influence of the crack position and the thermal-elastic non- homogeneous parameters on the TSIFs of modes I and 11 at the crack tip is presented. Results show that the variation of the thickness of the graded coating has a significant effect on the temperature jump across the crack surfaces when keeping the thickness of the substrate constant, and the thickness of functionally graded material （FGM） coating has a significant effect on the crack in the substrate. The results can be expected to be used for the purpose of gaining better understanding of the thermal-mechanical behavior of graded coatings.展开更多
TiB_(2)coatings can significantly enhance the high-temperature oxidation resistance of molybdenum,which would broaden the application range of molybdenum and alloys thereof.However,traditional methods for preparing Ti...TiB_(2)coatings can significantly enhance the high-temperature oxidation resistance of molybdenum,which would broaden the application range of molybdenum and alloys thereof.However,traditional methods for preparing TiB_(2)coatings have disadvantages such as high equipment costs,complicated processes,and highly toxic gas emissions.This paper proposes an environmentally friendly method,which requires inexpensive equipment and simple processing,for preparing TiB_(2)coating on molybdenum via electrophoretic deposition within Na3AlF6-based molten salts.The produced TiB_(2)layer had an approximate thickness of 60μm and exhibited high density,outstanding hardness(38.2 GPa)and robust adhesion strength(51 N).Additionally,high-temperature oxidation experiments revealed that,at900℃,the TiB_(2)coating provided effective protection to the molybdenum substrate against oxidation for 3 h.This result indicates that the TiB_(2)coating prepared on molybdenum using molten salt electrophoretic deposition possesses good high-temperature oxidation resistance.展开更多
YSZ/（Ni, Al） composite coatings were deposited on Inconel600 superalloy with ball peening （BP） and without （non BP）treatment using the electrophoretic deposition （EPD） technique, followed by vacuum sintering m...YSZ/（Ni, Al） composite coatings were deposited on Inconel600 superalloy with ball peening （BP） and without （non BP）treatment using the electrophoretic deposition （EPD） technique, followed by vacuum sintering method. The structures and phaseevolution of the coatings were studied with X-ray diffraction （XRD）, scanning electron microscopy （SEM） and energy dispersivespectrometry （EDS）. The relation between microstructures and properties of the BPs-coated samples was discussed. The results showthat the adhesion strength and gain mass of the BPs-coated samples with isothermal oxidation at 1100℃ for 100 h are 3.3 N and0.00817 mg/cm^2, respectively, while those of the non-BPs-coated sample are 2.6 N and 0.00559 mg/cm^2, respectively. The EDSmapping analysis indicates that an obvious outward diffusion of Cr from the substrate to BPs coated samples occurs after isothermaloxidation. The BPs-coated sample shows the superior adhesion and oxidation resistance compared with non-BPs-coated samples.展开更多
To reveal the influence of substrate/coating interdiffusion on the cyclic oxidation property of a metallic coating, cyclic oxida- tion behavior of an EB-PVD CoCrAIY coating on directionally solidified Ni-based superal...To reveal the influence of substrate/coating interdiffusion on the cyclic oxidation property of a metallic coating, cyclic oxida- tion behavior of an EB-PVD CoCrAIY coating on directionally solidified Ni-based superalloy DZ125 at 1 050℃ is investigated. The 40 μm thick CoCrA1Y coating has a cyclic oxidation life of around 160 h, and the oxidation constant is 1.915× 10^-7 mg4.cm^-8.s-1. However, severe spallation of the oxides containing Co, Cr, Ni, Ta and Ti occurs with longer cyclic oxidation. The degradation in oxidation resistance for the coating is related to the depletion of A1 due to the oxide spallation and interdiffu- sion. Severe interdiffusion between the coating and underlying substrate occurs at 1 050 ℃. The composition of the substrate has an important effect on the thermal cycling lifetime of the coating. The influencing mechanism is discussed.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
Developing advanced technologies to address the bacterial associated infections is an urgent requirement for metallic implants and devices.Here,we report a novel phosphonate/quaternary amine block polymer as the high-...Developing advanced technologies to address the bacterial associated infections is an urgent requirement for metallic implants and devices.Here,we report a novel phosphonate/quaternary amine block polymer as the high-efficiency antibacterial coating for metallic substrates.Three pDEMMP-b-pTMAEMA block polymers that bearing identical phosphonate segments(repeat units of 15)but varied cationic segments(repeat units of 8,45,and 70)were precisely prepared.Stable cationic polymer coatings were constructed on TC4 substrates based on the strong covalent binding between phosphonate group and metallic substrate.Robust relationship between the segment chain length of the polymer coating and the antibacterial property endowed to the substrates have been established based on quantitative and qualitative evaluations.Results showed that the antibacterial rate of the modified TC4 surface were 95.8%of S.aureus and 92.9%of E.coli cells attached.Interestingly,unlike the cationic free polymer or cationic hydrogels,the surface anchored cationic polymers do compromise the viability of the attached C2C12 cells but without significant cytotoxicity.In addition,the phosphonate/quate rnary amine block polymers can be easily constructed on titanium,stainless steel,and Ni/Cr alloy with significantly improved antibacterial property,indicating the generality of the block polymer for surface antibacterial modification of bio-metals.展开更多
The Cr-plated coating inside a gun barrel can effectively improve the barrel’s erosion resistance and thus increase the service life.However,due to the cyclic thermal load caused by high-temperature gunpowder,micro-e...The Cr-plated coating inside a gun barrel can effectively improve the barrel’s erosion resistance and thus increase the service life.However,due to the cyclic thermal load caused by high-temperature gunpowder,micro-element damage tends to occur within the Cr coating/steel substrate interface,leading to a gradual deterioration in macro-mechanical properties for the material in the related region.In order to mimic this cyclic thermal load and,thereby,study the thermal erosion behavior of the Cr coating on the barrel’s inner wall,a laser emitter is utilized in the current study.With the help of in-situ tensile test and finite element simulation results,a shear stress distribution law of the Cr coating/steel substrate and a change law of the interface ultimate shear strength are identified.Studies have shown that the Cr coating/steel substrate interface’s ultimate shear strength has a significant weakening effect due to increasing temperature.In this study,the interfacial ultimate shear strength decreases from 2.57 GPa(no erosion)to 1.02 GPa(laser power is 160 W).The data from this experiment is employed to establish a Cr coating/steel substrate interface shear damage model.And this model is used to predict the flaking process of Cr coating by finite element method.The simulation results show that the increase of coating crack spacing and coating thickness will increase the service life of gun barrel.展开更多
Hypereutectic Al-Si-Cu coatings were prepared by supersonic atmospheric plasma spraying to enhance the surface performance of lightweight alloys.To find out optimum process conditions and achieve desirable coatings,th...Hypereutectic Al-Si-Cu coatings were prepared by supersonic atmospheric plasma spraying to enhance the surface performance of lightweight alloys.To find out optimum process conditions and achieve desirable coatings,this work focuses on the influence of three important parameters(in-flight particle temperature,impact velocity,and substrate temperature)on the collected splats morphology coatings microstructure and microhardness.Results show that appropriate combinations of temperature and velocity of in-flight particles cannot only completely melt hypereutectic Al-Si-Cu particles especially the primary Si phase,but also provide the particles with sufficient kinetic energy.Thus,the optimized coating consists of 98.6%of fully-melted region with nanosized coupled eutectic and 0.9%of porosity.Increasing the substrate deposition temperature promotes the transition from inhomogeneous banded microstructure to homogeneous equiaxed microstructure with a lower porosity level.The observations are further interpreted by a newly developed phase-change heat transfer model on quantitatively revealing the solidification and remelting behaviors of several splats deposited on substrate Besides,phase evolutions including the formation of supersaturatedα-Al matrix solid solution,growth of Si and Al_(2)Cu phases at different process conditions are elaborated.An ideal microstructure(low fractions of unmelted/partially-melted regions and defects)together with solid solution,grain refinement and second phase strengthening effects contributes to the enhanced microhardness of coating.This integrated study not only provides a framework for optimizing Al-Si based coatings via thermal spraying but also gives valuable insights into the formation mechanisms of this class of coating materials.展开更多
Double glow plasma technique has a high deposition rate for preparing iridium coating. However, the glow plasma can influence the structure of the coating at the single substrate edge. In this study, the iridium coati...Double glow plasma technique has a high deposition rate for preparing iridium coating. However, the glow plasma can influence the structure of the coating at the single substrate edge. In this study, the iridium coating was prepared by double glow plasma on the surface of single niobium substrate. The microstructure of iridium coating at the substrate edge was observed by scanning electron microscopy. The composition of the coating was confirmed by energy dispersive spectroscopy and X-ray diffraction. There was a boundary between the coating and the substrate edge. The covered area for the iridium coating at the substrate edge became fewer and fewer from the inner area to the outer flange-area. The bamboo sprout-like particles on the surface of the substrate edge were composed of elemental niobium. The substrate edge was composed of the Nb coating and there was a transition zone between the Ir coating and the Nb coating. The interesting phenomenon of the substrate edge could be attributed to the effects of the bias voltages and the plasma cloud in the deposition chamber. The substrate edge effect could be mitigated or eliminated by adding lots of small niobium plates around the substrate in a deposition process.展开更多
The thermal barrier coatings with NiCrAlY alloy bonding layer, NiCrAlY Y 2O 3 stabilized ZrO 2 transition layer and Y 2O 3 stabilized ZrO 2 ceramic layer are prepared on nickel alloy substrates using the plasma spray ...The thermal barrier coatings with NiCrAlY alloy bonding layer, NiCrAlY Y 2O 3 stabilized ZrO 2 transition layer and Y 2O 3 stabilized ZrO 2 ceramic layer are prepared on nickel alloy substrates using the plasma spray technique. The relationship among the composition, structure and property of the coatings are investiga ted by means of optical microscope, scanning electronic microscope and the experiments of thermal shock resistance cycling and high temperature oxidation resistance. The results show that the structure design of introdu cing a transition layer between Ni alloy substrate and ZrO 2 ceramic coating guarantees the high quality and properties of the coatings; ZrO 2 coatings doped with a little SiO 2 possesses better thermal shock resistance and more excellent hot corrosion resistance as compared with ZrO 2 coating materials without SiO 2 ;the improvement in performance of ZrO 2 coating doped with SiO 2 is due to forming more dense coating structure by self closing effects of the flaws and pores in the ZrO 2 coatings.展开更多
Accident tolerant fuel(ATF) for the light water reactor has gained wide attentions after the Fukushima accident. To enhance the accident-tolerance of the nuclear system, one strategy is to modify the Zr-based alloy cl...Accident tolerant fuel(ATF) for the light water reactor has gained wide attentions after the Fukushima accident. To enhance the accident-tolerance of the nuclear system, one strategy is to modify the Zr-based alloy cladding surface with advanced ceramic coating. In this work, monolithic and dense Cr_2AlC coating has been synthesized by magnetron sputtering. The as-grown Cr_2AlC coating exhibits good chemical compatibility with Zr-based alloy substrate as well as mechanical integrity under both pull-off and scratch tests. The coating system also presents moderate thermochemical compatibility at 800℃ but degrades above 1000℃ under simulated loss-of-coolant accident(LOCA) conditions.展开更多
Three kinds of cast iron coatings were prepared by atmospheric plasma spraying. During the spraying, the mild steel substrate temperature was controlled to be averagely 50, 180, and 240℃, respectively. Abrasive wear ...Three kinds of cast iron coatings were prepared by atmospheric plasma spraying. During the spraying, the mild steel substrate temperature was controlled to be averagely 50, 180, and 240℃, respectively. Abrasive wear tests were conducted on the coatings under a dry friction condition. It is ibund that the abrasive wear resistance is enhanced with the substrate temperature increasing. SEM observations show that the wear losses of the coatings during the wear tests mainly result from the spalling of the splats. Furthermore, the improved wear resis- tance of the coatings mainly owes to the formation of oxides and the enhancement in the mechanical properties with the substrate temperature increasing.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
基金financially supported by the National Science and Technology Major Project(2017-VII-0012-0107)the China Postdoctoral Science Foundation(Nos.2019T120903 and 2018M631151)+5 种基金the Natural Science Foundation of Shaanxi Province(No.2019JQ-165)the Domain Foundation of Equipment Advance Research of 13th Five-year Plan(No.JZX7Y20190262062001)the Postdoctoral Science Foundation of Shaanxi Province(No.2018BSHYDZZ59)the opening foundation from Science and Technology on Plasma Dynamics Laboratory in Air Force Engineering University of China(No.61422020701)the Young Talent fund of University Association for Science and Technology in Shaanxi,China(No.20190403)The financial support from China Scholarship Council(CSC)to be a postdoctoral researcher in Forschungszentrum Jülich would be greatly appreciated by Dr.G.R.Li(No.201806285079)。
文摘Air plasma sprayed thermal barrier coatings(APS-TBCs)saw their wide application in high-temperaturerelated cutting-edge fields.The lamellar structure of APS-TBCs provides a significant advantage on thermal insulation.However,short life span is a major headache for APS-TBCs.This is highly related to the property changes and passive behaviors of the coatings during thermal service.Herein,a finite element model was developed to investigate the dynamic stiffening and substrate constraint on total spallation process.Results show that the stiffening accelerates the crack propagation of APS-TBCs.The driving force for crack propagation,which is characterized by strain energy release rate(SERR),is significantly enlarged.Consequently,the crack starts to propagate when the SERR exceeds the fracture toughness.In addition,the changing trends of SERR and crack propagation features are highly associated with temperatures.A higher temperature corresponds to more significant effect of stiffening on substrate constraint.In brief,temperature-dependent stiffening significantly aggravates the substrate constraint effect on APS-TBCs,which is one of the major causes for the spallation.Given that,lowering stiffening degree is essential to maintain high strain tolerance,and to further extend the life span of APS-TBCs.This understanding contributes to the development of advanced TBCs in future applications.
基金Funded by the International Science&Technology Cooperation Program of Hubei Province of China(No.2022EHB024)the National Key Research and Development Plan(Nos.2018YFE0103600 and 2021YFB3703100)+1 种基金the National Natural Science Foundation of China(Nos.51872212,51972244,52002075,and 52102066)the 111 Project(No.B13035)。
文摘Laser etching and laser chemical vapor deposition(LCVD)techniques were proposed for the rapid preparation of high-purity,strongly bonded SiC porous micro-nano-coatings on quartz substrates.The laser serves as an external driving force for the vertical growth of SiC whiskers,facilitating the formation of a porous nanostructure that resembles coral models found in the macroscopic biological world.The porous nanostructures are beneficial for reducing thermal expansion mismatch and relieving residual stress.It is capable of eliminating the cracks on the surface of SiC coatings as well as enhancing the bonding of SiC coatings with quartz substrates to avoid coating detachment.
基金the support by the National Natural Science Foundation of China(grant numbers 52273048 and 51973006)the Beijing Natural Science Foundation of China(grant number 2222052)the financial support of this work by BIOFIRESAFE(PID2020-117274RB-I00)funded by MINECO,Spain。
文摘Developing high-efficient flame-retardant coatings is crucial for fire safety polymer and battery fields.Traditional intumescent coatings and ceramifiable coatings struggle to provide immediate and prolonged protection simultaneously,which limits the applicability.To address this,an innovative bi-layered coating with organic/nano-inorganic additives is inspired by differential response behaviors,enabling relay response effect with both fast-acting and extended protection.Specifically,two layers function continuously in the form of a relay.With a mere 320 microns,the bi-layered coating withstands fire temperatures of up to 1400℃for at least 900 s.Consequently,the coating effective prevented burn through in aluminum plates and glass fabric-reinforced epoxy resin,which otherwise were burned through in 135 and 173 s,respectively.Meanwhile,the bi-layered coating suppressed the formation and decomposition of solid interface layer in lithium soft-package batteries,leading to prolonged electrochemical stability and fire safety.Additionally,the bi-layered coating with a fast response endows polyurethane foam with rapid self-extinguishing,preventing ignition even under exposure to strong fire of 1400℃.Shortly,our work offers new insights into the design and development of thin,high-performance,and multi-application flame-retardant coatings.
基金Project (51045004) supported by the National Natural Science Foundation of ChinaProject (2006AA03A219) supported by Hi-tech Research and Development Program of ChinaProject (YYYJ-0913) supported by Knowledge Innovation Project in Chinese Academy of Sciences
文摘Fe-based coating was produced on pure Ti substrate by the laser cladding technology. The composition and microstructure of the fabricated coating were analyzed by scanning electron microscopy （SEM）, X-ray diffraction （XRD） and transmission electron microscopy （TEM） technique. The tribological properties were tested through sliding against AISI52100 steel ball at different normal loads and sliding speeds. Besides, the morphologies of the worn surfaces and wear debris were analyzed by scanning electron microscopy （SEM） and three dimensional （3D） non-contact surface mapping. The results show that the prepared Fe-based coating has a high hardness of about 860 HV0.2 and exhibits an average wear rate of （0.70-2.32）×10-6 mm3/（N-m）, showing that the Fe-based coating can greatly improve the wear resistance of pure Ti substrate. The wear mechanism of the coating involves moderate adhesive and abrasive wear.
基金Projects(CKJB201205,QKJB201202,YJK201307)supported by the Nanjing Institute of Technology,China
文摘The outermost coating with single phase Ni2Al3 was obtained on copper surface by electrodepositing nickel followed by slurry pack aluminizing at 800 °C for 12 h. The oxidation resistance and microstructure of the coating oxidized in ambient air at 1000 °C for 25-250 h were investigated using SEM, X-ray diffraction and optical microscope methods. The results show that the copper with single phase Ni2Al3 coating possesses the best high temperature oxidation resistance, and the mass gain of the coating is 1/15 that of pure copper and 1/2 that of nickel coating, respectively. The specimen surface after being oxidized for 25 h still comprises Ni2Al3 phase. However, when the time of oxidizing treatment increases to 50 h, the Ni Al phase is formed. It is also found that the Ni2Al3 phase completely turns into Ni Al phase after oxidizing treatment for 100 h and above. The Ni Al coating shows excellent high temperature oxidation resistance when oxidation time is 250 h.
基金supported by National Basic Research Program of China(2012CB921504)Major Program of National Natural Science Foundation of China(51239005)+4 种基金National Natural Science Foundation of China(11404147,11174142)Natural Science Foundation of Jiangsu Province(BK20140519)China Postdoctoral Science Foundation(2015M571672)Research Fund for Advanced Talents of Jiangsu University(11JDG118)Training Project of Young Backbone Teachers of Jiangsu University
文摘The propagation characteristics of laser-generated like-Rayleigh waves in viscoelastic adhesive coating/substrate structures were studied.Considering the viscoelasticity of the coating and substrate,we have established the finite element models in frequency domain for the laser-generated like-Rayleigh waves in the epoxy coating/aluminum substrate,epoxy coating/brass substrate,and epoxy coating/foam substrate structures,respectively.In addition,we have investigated the waveform and propagation characteristics of the like-Rayleigh waves and studied the influences of the coating transparency,coating thickness,coating viscoelasticity,and substrate viscoelasticity on the propagation characteristics of the like-Rayleigh waves.Moreover,we have verified the results by the theoretical phase velocity and attenuation curves.The results show that the coating viscoelasticity induces the attenuation characteristics of the higher frequencies of the like-Rayleigh waves,but has little effect on the lower frequencies,and the substrate viscoelasticity has the influences on both the higher and lower frequencies of the like-Rayleigh waves,especially the lower frequencies.Furthermore,the mode and dispersive characteristics of the like-Rayleigh waves are closely related to the substrates.This study provides a useful theoretical basis for inverting mechanical parameters and evaluating the adhesive quality of the viscoelastic adhesive coating/substrate structures.
基金Project(2011B050400007)supported by the International Cooperation Program of Guangdong Province,China
文摘Ti/TiN/Zr/ZrN multilayer coatings were deposited on Cr_17Ni_2 steel substrates with different surface roughnesses by vacuum cathodic arc deposition method. Microstructure, micro-hardness, adhesion strength and cross-sectional morphology of the obtained multilayer coatings were investigated. The results show that the Vickers hardness of Ti/TiN/Zr/ZrN multilayer coating, with a film thickness of 11.37 μm, is 29.36 GPa. The erosion and salt spray resistance performance of Cr_17Ni_2 steel substrates can be evidently improved by Ti/TiN/Zr/ZrN multilayer coating. The surface roughness of Cr_17Ni_2 steel substrates plays an important role in determining the mechanical and erosion performances of Ti/TiN/Zr/ZrN multilayer coatings. Overall, a low value of the surface roughness of substrates corresponds to an improved performance of erosion and salt spray resistance of multilayer coatings. The optimized performance of Ti/TiN/Zr/ZrN multilayer coatings can be achieved provided that the surface roughness of Cr_17Ni_2 steel substrates is lower than 0.4μm.
基金The National Natural Science Foundation of China(No.10962008,51061015)Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20116401110002)
文摘This paper investigates the functionally graded coating bonded to an elastic strip with a crack under thermal- mechanical loading. Considering some new boundary conditions, it is assumed that the temperature drop across the crack surface is the result of the thermal conductivity index which controls heat conduction through the crack region. By the Fourier transforms, the thermal-elastic mixed boundary value problems are reduced to a system of singular integral equations which can be approximately solved by applying the Chebyshev polynomials. The numerical computation methods for the temperature, the displacement field and the thermal stress intensity factors （TSIFs） are presented. The normal temperature distributions （NTD） with different parameters along the crack surface are analyzed by numerical examples. The influence of the crack position and the thermal-elastic non- homogeneous parameters on the TSIFs of modes I and 11 at the crack tip is presented. Results show that the variation of the thickness of the graded coating has a significant effect on the temperature jump across the crack surfaces when keeping the thickness of the substrate constant, and the thickness of functionally graded material （FGM） coating has a significant effect on the crack in the substrate. The results can be expected to be used for the purpose of gaining better understanding of the thermal-mechanical behavior of graded coatings.
基金supported by the Original Exploratory Program of the National Natural Science Foundation of China(No.52450012)。
文摘TiB_(2)coatings can significantly enhance the high-temperature oxidation resistance of molybdenum,which would broaden the application range of molybdenum and alloys thereof.However,traditional methods for preparing TiB_(2)coatings have disadvantages such as high equipment costs,complicated processes,and highly toxic gas emissions.This paper proposes an environmentally friendly method,which requires inexpensive equipment and simple processing,for preparing TiB_(2)coating on molybdenum via electrophoretic deposition within Na3AlF6-based molten salts.The produced TiB_(2)layer had an approximate thickness of 60μm and exhibited high density,outstanding hardness(38.2 GPa)and robust adhesion strength(51 N).Additionally,high-temperature oxidation experiments revealed that,at900℃,the TiB_(2)coating provided effective protection to the molybdenum substrate against oxidation for 3 h.This result indicates that the TiB_(2)coating prepared on molybdenum using molten salt electrophoretic deposition possesses good high-temperature oxidation resistance.
基金Project(51271111)supported by the National Natural Science Foundation of ChinaProject(14KY0515)support by Graduate Research and Innovation Special Projects of Shanghai University of Engineering Science,China
文摘YSZ/（Ni, Al） composite coatings were deposited on Inconel600 superalloy with ball peening （BP） and without （non BP）treatment using the electrophoretic deposition （EPD） technique, followed by vacuum sintering method. The structures and phaseevolution of the coatings were studied with X-ray diffraction （XRD）, scanning electron microscopy （SEM） and energy dispersivespectrometry （EDS）. The relation between microstructures and properties of the BPs-coated samples was discussed. The results showthat the adhesion strength and gain mass of the BPs-coated samples with isothermal oxidation at 1100℃ for 100 h are 3.3 N and0.00817 mg/cm^2, respectively, while those of the non-BPs-coated sample are 2.6 N and 0.00559 mg/cm^2, respectively. The EDSmapping analysis indicates that an obvious outward diffusion of Cr from the substrate to BPs coated samples occurs after isothermaloxidation. The BPs-coated sample shows the superior adhesion and oxidation resistance compared with non-BPs-coated samples.
基金National Natural Science Foundation of China (50731001, 51071013, 51001032)National Basic Research Program of China (2010CB631200)
文摘To reveal the influence of substrate/coating interdiffusion on the cyclic oxidation property of a metallic coating, cyclic oxida- tion behavior of an EB-PVD CoCrAIY coating on directionally solidified Ni-based superalloy DZ125 at 1 050℃ is investigated. The 40 μm thick CoCrA1Y coating has a cyclic oxidation life of around 160 h, and the oxidation constant is 1.915× 10^-7 mg4.cm^-8.s-1. However, severe spallation of the oxides containing Co, Cr, Ni, Ta and Ti occurs with longer cyclic oxidation. The degradation in oxidation resistance for the coating is related to the depletion of A1 due to the oxide spallation and interdiffu- sion. Severe interdiffusion between the coating and underlying substrate occurs at 1 050 ℃. The composition of the substrate has an important effect on the thermal cycling lifetime of the coating. The influencing mechanism is discussed.
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the grant supports from the National Natural Science Foundation of China(No.21504046)the Six Talent Peaks Project in Jiangsu Province(SWYY-060)+1 种基金the Projects of Nanjing Normal University(No.184080H20192184080H10386)。
文摘Developing advanced technologies to address the bacterial associated infections is an urgent requirement for metallic implants and devices.Here,we report a novel phosphonate/quaternary amine block polymer as the high-efficiency antibacterial coating for metallic substrates.Three pDEMMP-b-pTMAEMA block polymers that bearing identical phosphonate segments(repeat units of 15)but varied cationic segments(repeat units of 8,45,and 70)were precisely prepared.Stable cationic polymer coatings were constructed on TC4 substrates based on the strong covalent binding between phosphonate group and metallic substrate.Robust relationship between the segment chain length of the polymer coating and the antibacterial property endowed to the substrates have been established based on quantitative and qualitative evaluations.Results showed that the antibacterial rate of the modified TC4 surface were 95.8%of S.aureus and 92.9%of E.coli cells attached.Interestingly,unlike the cationic free polymer or cationic hydrogels,the surface anchored cationic polymers do compromise the viability of the attached C2C12 cells but without significant cytotoxicity.In addition,the phosphonate/quate rnary amine block polymers can be easily constructed on titanium,stainless steel,and Ni/Cr alloy with significantly improved antibacterial property,indicating the generality of the block polymer for surface antibacterial modification of bio-metals.
文摘The Cr-plated coating inside a gun barrel can effectively improve the barrel’s erosion resistance and thus increase the service life.However,due to the cyclic thermal load caused by high-temperature gunpowder,micro-element damage tends to occur within the Cr coating/steel substrate interface,leading to a gradual deterioration in macro-mechanical properties for the material in the related region.In order to mimic this cyclic thermal load and,thereby,study the thermal erosion behavior of the Cr coating on the barrel’s inner wall,a laser emitter is utilized in the current study.With the help of in-situ tensile test and finite element simulation results,a shear stress distribution law of the Cr coating/steel substrate and a change law of the interface ultimate shear strength are identified.Studies have shown that the Cr coating/steel substrate interface’s ultimate shear strength has a significant weakening effect due to increasing temperature.In this study,the interfacial ultimate shear strength decreases from 2.57 GPa(no erosion)to 1.02 GPa(laser power is 160 W).The data from this experiment is employed to establish a Cr coating/steel substrate interface shear damage model.And this model is used to predict the flaking process of Cr coating by finite element method.The simulation results show that the increase of coating crack spacing and coating thickness will increase the service life of gun barrel.
基金financially supported by the National Natural Science Foundation of China(Nos.51535011,51675531,52075542 and 52075543)the Pre-Research Program in National 13th FiveYear Plan(No.61409230603)+2 种基金the Joint Fund of Ministry of Education for Pre-research of Equipment(No.6141A02033120)the China Postdoctoral Science Foundation(No.2019M653598)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2020JQ-911)。
文摘Hypereutectic Al-Si-Cu coatings were prepared by supersonic atmospheric plasma spraying to enhance the surface performance of lightweight alloys.To find out optimum process conditions and achieve desirable coatings,this work focuses on the influence of three important parameters(in-flight particle temperature,impact velocity,and substrate temperature)on the collected splats morphology coatings microstructure and microhardness.Results show that appropriate combinations of temperature and velocity of in-flight particles cannot only completely melt hypereutectic Al-Si-Cu particles especially the primary Si phase,but also provide the particles with sufficient kinetic energy.Thus,the optimized coating consists of 98.6%of fully-melted region with nanosized coupled eutectic and 0.9%of porosity.Increasing the substrate deposition temperature promotes the transition from inhomogeneous banded microstructure to homogeneous equiaxed microstructure with a lower porosity level.The observations are further interpreted by a newly developed phase-change heat transfer model on quantitatively revealing the solidification and remelting behaviors of several splats deposited on substrate Besides,phase evolutions including the formation of supersaturatedα-Al matrix solid solution,growth of Si and Al_(2)Cu phases at different process conditions are elaborated.An ideal microstructure(low fractions of unmelted/partially-melted regions and defects)together with solid solution,grain refinement and second phase strengthening effects contributes to the enhanced microhardness of coating.This integrated study not only provides a framework for optimizing Al-Si based coatings via thermal spraying but also gives valuable insights into the formation mechanisms of this class of coating materials.
基金supported by National Natural Science Foundation of China(50872055/E020703)Funding for Outstanding Doctoral Dissertation in NUAA(BCXJ11-09)+1 种基金the Fundamental Research Funds for the Central UniversitiesFunding of Jiangsu Innovation Program for Graduate Education of China(CXLX110207)
文摘Double glow plasma technique has a high deposition rate for preparing iridium coating. However, the glow plasma can influence the structure of the coating at the single substrate edge. In this study, the iridium coating was prepared by double glow plasma on the surface of single niobium substrate. The microstructure of iridium coating at the substrate edge was observed by scanning electron microscopy. The composition of the coating was confirmed by energy dispersive spectroscopy and X-ray diffraction. There was a boundary between the coating and the substrate edge. The covered area for the iridium coating at the substrate edge became fewer and fewer from the inner area to the outer flange-area. The bamboo sprout-like particles on the surface of the substrate edge were composed of elemental niobium. The substrate edge was composed of the Nb coating and there was a transition zone between the Ir coating and the Nb coating. The interesting phenomenon of the substrate edge could be attributed to the effects of the bias voltages and the plasma cloud in the deposition chamber. The substrate edge effect could be mitigated or eliminated by adding lots of small niobium plates around the substrate in a deposition process.
文摘The thermal barrier coatings with NiCrAlY alloy bonding layer, NiCrAlY Y 2O 3 stabilized ZrO 2 transition layer and Y 2O 3 stabilized ZrO 2 ceramic layer are prepared on nickel alloy substrates using the plasma spray technique. The relationship among the composition, structure and property of the coatings are investiga ted by means of optical microscope, scanning electronic microscope and the experiments of thermal shock resistance cycling and high temperature oxidation resistance. The results show that the structure design of introdu cing a transition layer between Ni alloy substrate and ZrO 2 ceramic coating guarantees the high quality and properties of the coatings; ZrO 2 coatings doped with a little SiO 2 possesses better thermal shock resistance and more excellent hot corrosion resistance as compared with ZrO 2 coating materials without SiO 2 ;the improvement in performance of ZrO 2 coating doped with SiO 2 is due to forming more dense coating structure by self closing effects of the flaws and pores in the ZrO 2 coatings.
基金supported by the National Natural Science Foundation of China under Grant Nos. 51402311 and 51772302the National Key R&D Program of China under Grant No. 2017YFB0703201
文摘Accident tolerant fuel(ATF) for the light water reactor has gained wide attentions after the Fukushima accident. To enhance the accident-tolerance of the nuclear system, one strategy is to modify the Zr-based alloy cladding surface with advanced ceramic coating. In this work, monolithic and dense Cr_2AlC coating has been synthesized by magnetron sputtering. The as-grown Cr_2AlC coating exhibits good chemical compatibility with Zr-based alloy substrate as well as mechanical integrity under both pull-off and scratch tests. The coating system also presents moderate thermochemical compatibility at 800℃ but degrades above 1000℃ under simulated loss-of-coolant accident(LOCA) conditions.
基金supported by the Special Fund for Basic Scientific Research of Central Colleges, Chang'an University (No.CHD2009JC131)
文摘Three kinds of cast iron coatings were prepared by atmospheric plasma spraying. During the spraying, the mild steel substrate temperature was controlled to be averagely 50, 180, and 240℃, respectively. Abrasive wear tests were conducted on the coatings under a dry friction condition. It is ibund that the abrasive wear resistance is enhanced with the substrate temperature increasing. SEM observations show that the wear losses of the coatings during the wear tests mainly result from the spalling of the splats. Furthermore, the improved wear resis- tance of the coatings mainly owes to the formation of oxides and the enhancement in the mechanical properties with the substrate temperature increasing.
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.
