The effects of Y_(2)O_(3) on the microstructure, microhardness, wear resistance, high-temperature oxidation resistance, hot corrosion resistance, and electrochemical corrosion behaviour of CoCrFeNiTiNb high entropy al...The effects of Y_(2)O_(3) on the microstructure, microhardness, wear resistance, high-temperature oxidation resistance, hot corrosion resistance, and electrochemical corrosion behaviour of CoCrFeNiTiNb high entropy alloy coatings formed on Ti-6Al-4V alloy surfaces were studied. The results show that the addition of Y_(2)O_(3) changes the proportion of the phase but does not change its type. The average grain size is only 1/4.7 of that of the high entropy alloy(HEA) coating, and the fine-grained strengthening leads to increases in the microhardness and wear resistance of 21.8% and 26.9%, respectively. The addition of Y_(2)O_(3) enhances the denseness and bonding properties of the oxide and corrosion product layers, reducing the oxidation and hot corrosion rates by 60.3% and 40.3%, respectively. The addition of Y_(2)O_(3) doubles the corrosion resistance which is attributed to the refinement of the grains, the increased proportion of HCP and TiN, and the weakening of galvanic coupling corrosion.展开更多
A Ni-based composite coating reinforced by in situ synthesized TiB2 and TiC particles was fabricated on Ti6A14V by laser cladding. An attempt was made to correlate the thermodynamic predictions and experimental observ...A Ni-based composite coating reinforced by in situ synthesized TiB2 and TiC particles was fabricated on Ti6A14V by laser cladding. An attempt was made to correlate the thermodynamic predictions and experimental observation. The micro- structure and the microhardness profile across the coating were investigated by means of X-ray diffraction （XRD）, scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, and a hardness tester. It is found that the coating mainly consists of a large number of reinforcements （black blocky TiB2, flower-like or equiaxial TiC, and fine acicular CrB） and the 7 matrix. The hardness of TiB2, TiC, and CrB reinforcements is much higher than that of the 7 matrix. The dispersive distribu- tion of such high hardness reinforcements causes the increase in hardness of the whole coating. The average value of the hard- ness is approximately Hv0.2 700 in the coating. The hardness of the coating is obviously higher than that of the substrate due to the dispersion strengthening of reinforcements.展开更多
NiCrxMoy(x=1,1.5;y=0,0.1,0.3)alloy coatings were prepared on the Q235 substrate by laser cladding under the protection of argon.The phase composition,microstructure,corrosion behavior,and mechanical properties of the ...NiCrxMoy(x=1,1.5;y=0,0.1,0.3)alloy coatings were prepared on the Q235 substrate by laser cladding under the protection of argon.The phase composition,microstructure,corrosion behavior,and mechanical properties of the NiCrxMoy alloy coatings were investigated using X-ray diffraction,scanning electron microscopy,transmission electron microscopy,electrochemical tests,X-ray photoelectron spectroscopy,microhardness,and nanoindentation tests.As the Cr content increased,the phase composition of the coatings changed from a single face-centered cubic(FCC)structure to a dual-phase structure coexisting with body-centered cubic(BCC)and FCC structures,while the addition of Mo promoted the precipitation ofσphase.The appearance of a homogeneous dual-phase structure and some amount ofσphase played a positive role in the corrosion resistance of NiCrxMoy coatings.Cr^3+ ions and Mo^6+ ions in the passive film enhanced the stability of the coatings.The nanoindentation tests showed that the nanohardness(6.71 GPa)and elastic modulus(184.40 GPa)of BCC phase were higher than those of the FCC phase(5.19 GPa and 155.26 GPa,respectively).Overall,the BCC phase andσphase improved the mechanical properties of the coatings.展开更多
FeCoCrNiA1Bx（x=0, 0.25, 0.50, 0.75） coatings were prepared by laser cladding to study the effects of boron on the structure and properties of high-entropy alloys coatings. The microstructure, microhardness, and wear...FeCoCrNiA1Bx（x=0, 0.25, 0.50, 0.75） coatings were prepared by laser cladding to study the effects of boron on the structure and properties of high-entropy alloys coatings. The microstructure, microhardness, and wear resistance properties of the samples were investigated by scanning electron microscopy, X-ray diffraction, metallographic micro-hardness test, and friction wear test, respectively, and the mechanism of the wear behavior was also analyzed. The results showed that the high-entropy alloys consisted of BCC phase and eutectic structure, which contained FCC phase and M2B. With boron addition, the content of BCC phase increased while that of eutectic structure decreased. The wear resistance of the high-entropy coatings was considerably improved with increasing addition of horon, and accordingly, the FeCoCrNiAlB0.75 coating showed the best wear resistance.展开更多
To solve the problems of deformation,micro-cracks,and residual tensile stress in laser cladding coatings,the technique of laser cladding with Fe-based memory alloy can be considered.However,the process of in-situ synt...To solve the problems of deformation,micro-cracks,and residual tensile stress in laser cladding coatings,the technique of laser cladding with Fe-based memory alloy can be considered.However,the process of in-situ synthesis of Fe-based memory alloy coatings is extremely complex.At present,there is no clear guidance scheme for its preparation process,which limits its promotion and application to some extent.Therefore,in this study,response surface methodology(RSM)was used to model the response surface between the target values and the cladding process parameters.The NSGA-2 algorithm was employed to optimize the process parameters.The results indicate that the composite optimization method consisting of RSM and the NSGA-2 algorithm can establish a more accurate model,with an error of less than 4.5%between the predicted and actual values.Based on this established model,the optimal scheme for process parameters corresponding to different target results can be rapidly obtained.The prepared coating exhibits a uniform structure,with no defects such as pores,cracks,and deformation.The surface roughness and microhardness of the coating are enhanced,the shaping quality of the coating is effectively improved,and the electrochemical corrosion performance of the coating in 3.5%NaCl solution is obviously better than that of the substrate,providing an important guide for engineering applications.展开更多
Wear-resistant Fe-based coating was prepared by high-speed laser cladding on bainitic steel.The influence of laser scanning speed on microstructure,microhardness,and wear resistance of cladding coating was investigate...Wear-resistant Fe-based coating was prepared by high-speed laser cladding on bainitic steel.The influence of laser scanning speed on microstructure,microhardness,and wear resistance of cladding coating was investigated.Scanning electron microscopy results showed that the coating was mainly composed of dendrite and interdendrite.Scanning electron microscope images were converted by binary algorithm to facilitate statistics of dendrite and interdendrite area.Statistical results indicate that by accelerating the scanning speed,the interdendrite eutectic structure increased.According to energydispersive X-ray spectroscopy and X-ray diffraction results,the interdendrite was enriched with elements Cr,Mo,and B,and main structures in the coating wereα-Fe,γ-Fe,and M(23)C_(6).The hardness of the coating was much higher than that of the substrate.Elements diffused from coating to substrate,resulting in a transition zone of hardness.Moreover,with an increase in the scanning speed,the diffusion of elements at the coating–matrix interface decreased,while the hardness and wear resistance of the coating increased.Grain refinement and interdendrite(γ-Fe,M_(23)C_(6))increasing due to high scanning speed were the major contributors to the increase in hardness and wear resistance.展开更多
A TiB2 and TiC particles reinforced Ni based composites coating was prepared on TC4 alloy surface by chemical reaction among Ti, B and C elements using laser cladding technique. Microstructural analysis showed that th...A TiB2 and TiC particles reinforced Ni based composites coating was prepared on TC4 alloy surface by chemical reaction among Ti, B and C elements using laser cladding technique. Microstructural analysis showed that the sizes of in-situ synthesized TiB2 and TiC particles ranged within 5~10um and l^2um, respectively, while both the two kinds of particles were uniformly distributed in the clad layer. The measurement of microhardness and wear and friction properties indicated that the microhardness of laser clad layer was HV900-1100, being three times of that of the TC4 alloy; the friction coefficient of the laser clad layer in air and in vacuum (10~5 Pa) ranged within 0.2-0.3 and 0.3-0.5, respectively; the wear rate in terms of mass loss was considerably lower than that of the TC4 alloy both in air and in vacuum environment.展开更多
To select the proper composition and obtain an overall material?microstructure?property relationship for Cu?Fe alloy, theeffect of Fe content on microstructure and properties of Cu?Fe-based composite coatings by laser...To select the proper composition and obtain an overall material?microstructure?property relationship for Cu?Fe alloy, theeffect of Fe content on microstructure and properties of Cu?Fe-based composite coatings by laser induction hybrid rapid claddingwas investigated. Microstructure characterization of the composite coatings was tested utilizing SEM, XRD and EDS. Microhardnessmeasurement was executed to evaluate the mechanical properties of the composite coatings. The results show that for low Fe content,the composite coating presents a feature that Fe-rich equiaxed dendrites are embedded in the Cu-rich matrix. With increasing Fecontent, the Fe-rich particles are dispersed in the Cu-rich matrix. With further increasing Fe content, large amounts of Cu-richparticles are homogeneously dispersed in the interdendrite of the Fe-rich matrix. Correspondingly, the average microhardness of thecomposite coatings increases gradually with the increase of Fe content and the microhardness of Cu14.5Fe83Si2C0.5 coating is muchtwice higher than that of the substrate.展开更多
Thin metallic layers (~ 2 μm) of Ni were deposited on polycrystalline Al2O3. ZrO2 and (Ce-TZP)+Al2O3 ceramic substrates. and further irradiated with pulsed excimer (Xeno chloride) laser pulses. The laser energy densi...Thin metallic layers (~ 2 μm) of Ni were deposited on polycrystalline Al2O3. ZrO2 and (Ce-TZP)+Al2O3 ceramic substrates. and further irradiated with pulsed excimer (Xeno chloride) laser pulses. The laser energy density was varied from 0.21 to 0.81 J / cm2 to optimize bending strength. For ZrO2 ceramic, it was found that the strength increases from 530 to 753 MPa at 0.51 J / cm2 irradiation. For Al2O3 and (Ce-TZP)+ Al2O3 the fracture strength also increases in varying degree. The causes of strength increment were discussed.展开更多
TiB2/TiB/TiNx(x=1,0.3)/Ti composite coating was prepared on pure Ti by laser surface alloying by using powders of boron as starting materials.The composite coating was examined by X-ray diffraction(XRD),high-resolutio...TiB2/TiB/TiNx(x=1,0.3)/Ti composite coating was prepared on pure Ti by laser surface alloying by using powders of boron as starting materials.The composite coating was examined by X-ray diffraction(XRD),high-resolution transmission electron microscopy(HRTEM)and scanning electron microscopy(SEM).The friction and wear properties of the composite coating were examined using a pin-on-disk tester under dry sliding wear condition.The results showed that the top surface of the composite coating was mainly composed of TiB2,TiB,TiN0.3,TiN and Ti phases,while the interface of the composite coating was composed of TiB and Ti phases.The composite coating showed sticklike structure near the top surface,and dendrites structure near the interface.The friction and wear test showed that the composite coating had better wear resistance than pure Ti due to their higher microhardness than that of pure Ti substrate.展开更多
To evaluate the potential of high entropy alloys for marine applications,a new high entropy alloy coating of AlCrFeNiW_(0.2)Ti_(0.5)was designed and produced on Q235 steel via laser cladding.The microstructure,microha...To evaluate the potential of high entropy alloys for marine applications,a new high entropy alloy coating of AlCrFeNiW_(0.2)Ti_(0.5)was designed and produced on Q235 steel via laser cladding.The microstructure,microhardness and tribological performances sliding against YG6 cemented carbide,GCr15 steel and Si_(3)N_(4)ceramic in seawater were studied in detail.The AlCrFeNiW_(0.2)Ti_(0.5)coating showed an anomalous’sunflower-like’morphology and consisted of BCC and ordered B2 phases.The microhardness was approximately 692.5 HV,which was 5 times higher than substrate.The coating showed more excellent tribological performances than Q235 steel and SUS304,a typical material used in seawater environment,sliding against all three coupled balls in seawater.Besides,the wear and friction of AlCrFeNiW_(0.2)Ti_(0.5)coating sliding against YG6 in seawater were most mild.The main reason was the generation of Mg(OH)_(2),CaCO_(3),metal oxides and hydroxides and the formation of protective tribo-film on the worn surface of AlCrFeNiW_(0.2)Ti_(0.5)coating in the process of reciprocated sliding.This would effectively hinder the direct contact between the worn surfaces of AlCrFeNiW_(0.2)Ti_(0.5)coating and YG6 ball,resulting in a decrease of friction coefficient and wear rate.Thus the YG6 was an ideal coupled material for AlCrFeNiW_(0.2)Ti_(0.5)coating in seawater,and the coating would become a promising wear-resisting material in ocean environment.展开更多
The microstructure,microhardness,and corrosion resistance of laser cladding Ni−WC coating on the surface of AlSi5Cu1Mg alloy were investigated by scanning electron microscopy,X-ray diffraction,microhardness testing,im...The microstructure,microhardness,and corrosion resistance of laser cladding Ni−WC coating on the surface of AlSi5Cu1Mg alloy were investigated by scanning electron microscopy,X-ray diffraction,microhardness testing,immersion corrosion testing,and electrochemical measurement.The results show that a smooth coating containing NiAl,Ni_(3)Al,M_(7)C_(3),M_(23)C_(6)phases(M=Ni,Al,Cr,W,Fe)and WC particles is prepared by laser cladding.Under a laser scanning speed of 120 mm/min,the microhardness of the cladding coating is 9−11 times that of AlSi5Cu1Mg,due to the synergistic effect of excellent metallurgical bond and newly formed carbides.The Ni−WC coating shows higher corrosion potential(−318.09 mV)and lower corrosion current density(12.33μA/cm^(2))compared with the matrix.The crack-free,dense cladding coating obviously inhibits the penetration of Cl^(−)and H^(+),leading to the remarkedly improved corrosion resistance of cladding coating.展开更多
Titanium-based composite coatings with and without Y particles were deposited by laser cladding on Ti6Al4V substrates. Solidification microstructure,phase constituents and distribution of the reinforcements with diffe...Titanium-based composite coatings with and without Y particles were deposited by laser cladding on Ti6Al4V substrates. Solidification microstructure,phase constituents and distribution of the reinforcements with different morphologies,were investigated by X-ray diffractometer （XRD）,scanning electron microscopy （SEM） and electron probe micro analyzer （EPMA）. In addition,the effects of the addition of Y on mechanical properties （in terms of microhardness and the cracking susceptibility） were also highlighted. The results showed that the coatings were composed of α-Ti cellular dendrites,coarse needle-shaped TiB phase and an eutectic in which a large number of needle-shaped TiB whiskers and a few equiaxial TiC particles were uniformly embedded. Y was not stable and was transformed into Y2O3 during laser cladding. The addition of Y could refine the microstructure of the coating by hastening the spheroidization of primary phase structure. Moreover,it could also decrease the activity of carbon and prevent solute atoms from traversing the interface and moving into primary phase structure,namely,increase the fraction volume of TiC in the coating. All of there factors made the cracking susceptibility of the coating containing Y reduced on the premise that microhardness of the coating was increased. Microhardness of the coating without Y ranged from HV 875.6 to HV 659.8,the average microhardness was about HV 747.9. For the coating with Y,microhardness changed from HV 876.5 to HV 741.5 and the average michardness was about HV 795.3. Fracture toughness of the upper,middle,bottom and interface of the coating without Y were 6.33,8.91,11.94 and 11.93 MPa.m1/2. Fracture toughness of the similar positions of the coating with Y were 8.58,12.93,13.81,17.11 MPa.m1/2,respectively. The coating with Y presented higher microhardness and fracture toughness in comparison with that without Y. Obviously,the addition of Y had a very positive effect on the microstructure and mechanical properties of the coatings.展开更多
Laser cladding is a new surface repair method that can improve the wear and corrosion resistance of substrate surfaces.However,the cladding layer typically exhibits a rough surface,high hardness and large residual ten...Laser cladding is a new surface repair method that can improve the wear and corrosion resistance of substrate surfaces.However,the cladding layer typically exhibits a rough surface,high hardness and large residual tensile stress,and thus requires further machining and finishing.Ultrasonic rolling(U-rolling)is a highly efficient finishing and strengthening process that combines ultrasonic technology with traditional rolling(T-rolling).In this study,an ironbased alloy was coated onto the surface of H13 die steel using laser cladding,and the surface of the cladding layer was polished using U-rolling.The effects of U-rolling on the surface quality,corrosion resistance and friction and wear properties of the laser-cladding layer were investigated and compared with those obtained by T-rolling.The surface roughness of the U-rolled sample was only 1/4 that of the T-rolled sample.The hardness and residual compressive stress of the laser cladding layer after U-rolling were higher than those after T-rolling.Similarly,the surface corrosion resistance of the laser cladding layer after U-rolling was higher than that after T-rolling.U-rolling changed the surface roughness,grain size,and residual stress of the material and thus affected the corrosion resistance of the laser cladding layer.The friction coefficient and wear rate of the U-rolled surface of the cladding layer were lower than those of the T-rolled surface.In addition,the tribological properties of the cladding layer were found to be related to the rolling direction.When the friction direction of the sample was the same as the rolling direction,its friction and wear performance were higher than those when the two directions were perpendicular.展开更多
A titanium-based composite coating reinforced by in situ synthesized TiB and TiC particles was fabricated on Ti6A14V by laser cladding. The microstructure and mechanical properties were investigated. The coating was m...A titanium-based composite coating reinforced by in situ synthesized TiB and TiC particles was fabricated on Ti6A14V by laser cladding. The microstructure and mechanical properties were investigated. The coating was mainly composed of a-Ti cellular dendrites and an eutectic in which a large number of rod/ needle-shaped TiB and a few equiaxial TiC particles were homogeneously embedded. The microstructural evolution could be divided into four stages： precipitation and growth of primary fl-Ti phase, formation of the binary eutectic fl-Ti＋TiB, formation of the ternary eutectic fl-Ti＋TiB＋TiC, and solid transformation from fl-Ti to a-Ti. Microhardness of the coating showed a gradient variation from the surface （about HV0.2 876） to the bottom （about HV0.2 660） and was prominently improved in comparison with that of the substrate. Fracture toughness of the coating also exhibited a gradient variation from the surface （6.3 MPa-m1/2） to the interface （11.9 MPa-mV2）. Wear resistance of the coating was significantly superior to that of Ti6A14V.展开更多
The latest progress and research status of laser cladding ceramic coating was summarized. Technique characteristics and influence factors of laser cladding technique were introduced. Laser cladding technique includes ...The latest progress and research status of laser cladding ceramic coating was summarized. Technique characteristics and influence factors of laser cladding technique were introduced. Laser cladding technique includes the mixing method and laser irradiation. The mixing method can be classified as pre-coating method and synchronization method. The technique parameters include size of facula, scanning speed, cladding sector and times, adding quantity of powder, thickness of coating and quantity of joint coating. The results show that proper technique parameters can be controlled in order to acquire high quality laser cladding coating. Strengthened effect mechanism of rare earth additive is concluded, and the main effects of rare earth additive are micro-alloying, purifying boundary, fining crystal grains, improving crystal boundary, restraining columnar crystal growing. The development of laser cladding ceramic coating research was discussed.展开更多
A bonding approach based on laser surface modification was developed to address the poor bonding be-tween Si_(3)N_(4) ceramic and Cu.The bonding mechanism in Si_(3)N_(4)/Cu heterogeneous composite structure fabricated...A bonding approach based on laser surface modification was developed to address the poor bonding be-tween Si_(3)N_(4) ceramic and Cu.The bonding mechanism in Si_(3)N_(4)/Cu heterogeneous composite structure fabricated by laser modification-assisted bonding is examined by means of scanning/transmission elec-tron microscopy and thermodynamic analysis.In the bonding process under laser modification,atomic intermixing at the interface is confirmed,as a result of the enhanced diffusion assisted by the dissocia-tion of Si_(3)N_(4) ceramic by laser.The dissociating Si precipitations on the surface,as well as the formation of micro-pores interfacial structure,would be the key concept of the bonding,by which the seamless and robust heterointerfaces were created.By controlling the laser-modifying conditions,we can obtain a reli-able heterostructure via the optimization of the trade-off of the surface structure and bonding strength,as determined by the laser-modified surface prior to bonding.The maximum structure depth and S ratio at the Si_(3)N_(4) surface were produced at a laser power of 56 W,corresponding to the maximal shear strength of 15.26 MPa.It is believed that the further development of this bonding technology will advance power electronic substrate fabrication applied in high-power devices.展开更多
Hard coatings are extensively required in industry for protecting mechanical/structural parts that withstand extremely high temperature,stress,chemical corrosion,and other hostile environments.Electrical discharge coa...Hard coatings are extensively required in industry for protecting mechanical/structural parts that withstand extremely high temperature,stress,chemical corrosion,and other hostile environments.Electrical discharge coating(EDC)is an emerging surface modification technology to produce such hard coatings by using electrical discharges to coat a layer of material on workpiece surface to modify and enhance the surface characteristics or create new surface functions.This paper presents a comprehensive overview of EDC technologies for various materials,and summarises the types and key parameters of EDC processes as well as the characteristics of resulting coatings.It provides a systematic summary of the fundamentals and key features of the EDC processes,as well as its applications and future trends.展开更多
（Ti, Nb）C reinforced Fe based laser coatings were prepared with normal and high scanning velocities of the laser beam. The distribution characteristics of reinforced particles in the coatings were investigated. The ...（Ti, Nb）C reinforced Fe based laser coatings were prepared with normal and high scanning velocities of the laser beam. The distribution characteristics of reinforced particles in the coatings were investigated. The mechanical properties of coatings were tested. The results showed that the morphologies of the microstructure and the reinforced particle changed dramatically at high solidification rate due to rapid laser processing compared with that prepared by normal processing. Two kinds of particles were observed in the coating. One was （Ti, Nb）C multiple carbide particle with the size of micron and sub micron scales, in which a mass of dislocations were found. Another was nano sized particle including a Fe and （Ti, Nb）C obtained by rapid solidification. The microstructure of the coatings was highly refined and a large number of twin crystals were found in matrix. The resuhs of mechanical properties test revealed that the wear resistance of the coaling was improved by rapid laser processing, compared with that of the coating prepared with normal speeds. The ahove-mentioned conclusion indicated that rapid laser cladding can promote not on ly the processing efficiency but also lhe mechanical properties of the coating.展开更多
基金Project supported by the National Natural Science Foundation of China(51805285,51605237)the projects of Shandong Province"Youth Innovation Science and Technology Support Plan"(2021KJ026)+1 种基金the Key Research and Development Project of Shandong Province(2018GGX103031)the Natural Science Foundation of Shandong Province(ZR2021ME023)。
文摘The effects of Y_(2)O_(3) on the microstructure, microhardness, wear resistance, high-temperature oxidation resistance, hot corrosion resistance, and electrochemical corrosion behaviour of CoCrFeNiTiNb high entropy alloy coatings formed on Ti-6Al-4V alloy surfaces were studied. The results show that the addition of Y_(2)O_(3) changes the proportion of the phase but does not change its type. The average grain size is only 1/4.7 of that of the high entropy alloy(HEA) coating, and the fine-grained strengthening leads to increases in the microhardness and wear resistance of 21.8% and 26.9%, respectively. The addition of Y_(2)O_(3) enhances the denseness and bonding properties of the oxide and corrosion product layers, reducing the oxidation and hot corrosion rates by 60.3% and 40.3%, respectively. The addition of Y_(2)O_(3) doubles the corrosion resistance which is attributed to the refinement of the grains, the increased proportion of HCP and TiN, and the weakening of galvanic coupling corrosion.
基金supported by the National Natural Science Foundation of China (No. 51002093)Shanghai Science and Technology Development Foundation (No. 08QA14035)Shanghai Leading Academic Discipline Project (No. J51402)
文摘A Ni-based composite coating reinforced by in situ synthesized TiB2 and TiC particles was fabricated on Ti6A14V by laser cladding. An attempt was made to correlate the thermodynamic predictions and experimental observation. The micro- structure and the microhardness profile across the coating were investigated by means of X-ray diffraction （XRD）, scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, and a hardness tester. It is found that the coating mainly consists of a large number of reinforcements （black blocky TiB2, flower-like or equiaxial TiC, and fine acicular CrB） and the 7 matrix. The hardness of TiB2, TiC, and CrB reinforcements is much higher than that of the 7 matrix. The dispersive distribu- tion of such high hardness reinforcements causes the increase in hardness of the whole coating. The average value of the hard- ness is approximately Hv0.2 700 in the coating. The hardness of the coating is obviously higher than that of the substrate due to the dispersion strengthening of reinforcements.
基金financially supported by the Distinguished Taishan Scholars in Climbing Plan(No.tspd2O161OO6)the National Natural Science Foundation of China(Nos.51772176 and 51971121).
文摘NiCrxMoy(x=1,1.5;y=0,0.1,0.3)alloy coatings were prepared on the Q235 substrate by laser cladding under the protection of argon.The phase composition,microstructure,corrosion behavior,and mechanical properties of the NiCrxMoy alloy coatings were investigated using X-ray diffraction,scanning electron microscopy,transmission electron microscopy,electrochemical tests,X-ray photoelectron spectroscopy,microhardness,and nanoindentation tests.As the Cr content increased,the phase composition of the coatings changed from a single face-centered cubic(FCC)structure to a dual-phase structure coexisting with body-centered cubic(BCC)and FCC structures,while the addition of Mo promoted the precipitation ofσphase.The appearance of a homogeneous dual-phase structure and some amount ofσphase played a positive role in the corrosion resistance of NiCrxMoy coatings.Cr^3+ ions and Mo^6+ ions in the passive film enhanced the stability of the coatings.The nanoindentation tests showed that the nanohardness(6.71 GPa)and elastic modulus(184.40 GPa)of BCC phase were higher than those of the FCC phase(5.19 GPa and 155.26 GPa,respectively).Overall,the BCC phase andσphase improved the mechanical properties of the coatings.
基金funded by National Natural Science Foundation of China(No.51301112)Natural Science Foundation of Liaoning Province of China (No.201602553)Science Research Program of Education Department in Liaoning Province of China (No.L2014048)
文摘FeCoCrNiA1Bx（x=0, 0.25, 0.50, 0.75） coatings were prepared by laser cladding to study the effects of boron on the structure and properties of high-entropy alloys coatings. The microstructure, microhardness, and wear resistance properties of the samples were investigated by scanning electron microscopy, X-ray diffraction, metallographic micro-hardness test, and friction wear test, respectively, and the mechanism of the wear behavior was also analyzed. The results showed that the high-entropy alloys consisted of BCC phase and eutectic structure, which contained FCC phase and M2B. With boron addition, the content of BCC phase increased while that of eutectic structure decreased. The wear resistance of the high-entropy coatings was considerably improved with increasing addition of horon, and accordingly, the FeCoCrNiAlB0.75 coating showed the best wear resistance.
基金financial supports from the National Natural Science Foundation of China-Youth Project(51801076)the Provincial Colleges and Universities Natural Science Research Project of Jiangsu Province(18KJB430009)+1 种基金the Postdoctoral Research Support Project of Jiangsu Province(1601055C)the Senior Talents Research Startup of Jiangsu University(14JDG126)。
文摘To solve the problems of deformation,micro-cracks,and residual tensile stress in laser cladding coatings,the technique of laser cladding with Fe-based memory alloy can be considered.However,the process of in-situ synthesis of Fe-based memory alloy coatings is extremely complex.At present,there is no clear guidance scheme for its preparation process,which limits its promotion and application to some extent.Therefore,in this study,response surface methodology(RSM)was used to model the response surface between the target values and the cladding process parameters.The NSGA-2 algorithm was employed to optimize the process parameters.The results indicate that the composite optimization method consisting of RSM and the NSGA-2 algorithm can establish a more accurate model,with an error of less than 4.5%between the predicted and actual values.Based on this established model,the optimal scheme for process parameters corresponding to different target results can be rapidly obtained.The prepared coating exhibits a uniform structure,with no defects such as pores,cracks,and deformation.The surface roughness and microhardness of the coating are enhanced,the shaping quality of the coating is effectively improved,and the electrochemical corrosion performance of the coating in 3.5%NaCl solution is obviously better than that of the substrate,providing an important guide for engineering applications.
基金the National Key Research and Development Program of China(2017YFB0304504)the Fundamental Research Funds for the Central Universities(2019JBM044).
文摘Wear-resistant Fe-based coating was prepared by high-speed laser cladding on bainitic steel.The influence of laser scanning speed on microstructure,microhardness,and wear resistance of cladding coating was investigated.Scanning electron microscopy results showed that the coating was mainly composed of dendrite and interdendrite.Scanning electron microscope images were converted by binary algorithm to facilitate statistics of dendrite and interdendrite area.Statistical results indicate that by accelerating the scanning speed,the interdendrite eutectic structure increased.According to energydispersive X-ray spectroscopy and X-ray diffraction results,the interdendrite was enriched with elements Cr,Mo,and B,and main structures in the coating wereα-Fe,γ-Fe,and M(23)C_(6).The hardness of the coating was much higher than that of the substrate.Elements diffused from coating to substrate,resulting in a transition zone of hardness.Moreover,with an increase in the scanning speed,the diffusion of elements at the coating–matrix interface decreased,while the hardness and wear resistance of the coating increased.Grain refinement and interdendrite(γ-Fe,M_(23)C_(6))increasing due to high scanning speed were the major contributors to the increase in hardness and wear resistance.
文摘A TiB2 and TiC particles reinforced Ni based composites coating was prepared on TC4 alloy surface by chemical reaction among Ti, B and C elements using laser cladding technique. Microstructural analysis showed that the sizes of in-situ synthesized TiB2 and TiC particles ranged within 5~10um and l^2um, respectively, while both the two kinds of particles were uniformly distributed in the clad layer. The measurement of microhardness and wear and friction properties indicated that the microhardness of laser clad layer was HV900-1100, being three times of that of the TC4 alloy; the friction coefficient of the laser clad layer in air and in vacuum (10~5 Pa) ranged within 0.2-0.3 and 0.3-0.5, respectively; the wear rate in terms of mass loss was considerably lower than that of the TC4 alloy both in air and in vacuum environment.
基金Projects(51471084,61475117)supported by the National Natural Science Foundation of ChinaProject(13ZCZDGX01109)supported by Tianjin Municipal Science and Technology Commission of ChinaProject(20122BBE500031)supported by the Key Technology Project of Jiangxi Province in China
文摘To select the proper composition and obtain an overall material?microstructure?property relationship for Cu?Fe alloy, theeffect of Fe content on microstructure and properties of Cu?Fe-based composite coatings by laser induction hybrid rapid claddingwas investigated. Microstructure characterization of the composite coatings was tested utilizing SEM, XRD and EDS. Microhardnessmeasurement was executed to evaluate the mechanical properties of the composite coatings. The results show that for low Fe content,the composite coating presents a feature that Fe-rich equiaxed dendrites are embedded in the Cu-rich matrix. With increasing Fecontent, the Fe-rich particles are dispersed in the Cu-rich matrix. With further increasing Fe content, large amounts of Cu-richparticles are homogeneously dispersed in the interdendrite of the Fe-rich matrix. Correspondingly, the average microhardness of thecomposite coatings increases gradually with the increase of Fe content and the microhardness of Cu14.5Fe83Si2C0.5 coating is muchtwice higher than that of the substrate.
文摘Thin metallic layers (~ 2 μm) of Ni were deposited on polycrystalline Al2O3. ZrO2 and (Ce-TZP)+Al2O3 ceramic substrates. and further irradiated with pulsed excimer (Xeno chloride) laser pulses. The laser energy density was varied from 0.21 to 0.81 J / cm2 to optimize bending strength. For ZrO2 ceramic, it was found that the strength increases from 530 to 753 MPa at 0.51 J / cm2 irradiation. For Al2O3 and (Ce-TZP)+ Al2O3 the fracture strength also increases in varying degree. The causes of strength increment were discussed.
基金National Natural Science Foundations of China(51045004)
文摘TiB2/TiB/TiNx(x=1,0.3)/Ti composite coating was prepared on pure Ti by laser surface alloying by using powders of boron as starting materials.The composite coating was examined by X-ray diffraction(XRD),high-resolution transmission electron microscopy(HRTEM)and scanning electron microscopy(SEM).The friction and wear properties of the composite coating were examined using a pin-on-disk tester under dry sliding wear condition.The results showed that the top surface of the composite coating was mainly composed of TiB2,TiB,TiN0.3,TiN and Ti phases,while the interface of the composite coating was composed of TiB and Ti phases.The composite coating showed sticklike structure near the top surface,and dendrites structure near the interface.The friction and wear test showed that the composite coating had better wear resistance than pure Ti due to their higher microhardness than that of pure Ti substrate.
基金financially supported by the National Natural Science Foundation of China(Nos.51771041,51774065,51671044 and 51901116)the National Key Research and Development Program of China(No.2017YFA0403803)。
文摘To evaluate the potential of high entropy alloys for marine applications,a new high entropy alloy coating of AlCrFeNiW_(0.2)Ti_(0.5)was designed and produced on Q235 steel via laser cladding.The microstructure,microhardness and tribological performances sliding against YG6 cemented carbide,GCr15 steel and Si_(3)N_(4)ceramic in seawater were studied in detail.The AlCrFeNiW_(0.2)Ti_(0.5)coating showed an anomalous’sunflower-like’morphology and consisted of BCC and ordered B2 phases.The microhardness was approximately 692.5 HV,which was 5 times higher than substrate.The coating showed more excellent tribological performances than Q235 steel and SUS304,a typical material used in seawater environment,sliding against all three coupled balls in seawater.Besides,the wear and friction of AlCrFeNiW_(0.2)Ti_(0.5)coating sliding against YG6 in seawater were most mild.The main reason was the generation of Mg(OH)_(2),CaCO_(3),metal oxides and hydroxides and the formation of protective tribo-film on the worn surface of AlCrFeNiW_(0.2)Ti_(0.5)coating in the process of reciprocated sliding.This would effectively hinder the direct contact between the worn surfaces of AlCrFeNiW_(0.2)Ti_(0.5)coating and YG6 ball,resulting in a decrease of friction coefficient and wear rate.Thus the YG6 was an ideal coupled material for AlCrFeNiW_(0.2)Ti_(0.5)coating in seawater,and the coating would become a promising wear-resisting material in ocean environment.
文摘The microstructure,microhardness,and corrosion resistance of laser cladding Ni−WC coating on the surface of AlSi5Cu1Mg alloy were investigated by scanning electron microscopy,X-ray diffraction,microhardness testing,immersion corrosion testing,and electrochemical measurement.The results show that a smooth coating containing NiAl,Ni_(3)Al,M_(7)C_(3),M_(23)C_(6)phases(M=Ni,Al,Cr,W,Fe)and WC particles is prepared by laser cladding.Under a laser scanning speed of 120 mm/min,the microhardness of the cladding coating is 9−11 times that of AlSi5Cu1Mg,due to the synergistic effect of excellent metallurgical bond and newly formed carbides.The Ni−WC coating shows higher corrosion potential(−318.09 mV)and lower corrosion current density(12.33μA/cm^(2))compared with the matrix.The crack-free,dense cladding coating obviously inhibits the penetration of Cl^(−)and H^(+),leading to the remarkedly improved corrosion resistance of cladding coating.
基金Project supported by the National Natural Science Foundation of China (51002093)the Shanghai Science and Technology Development Foun-dation, China (08QA14035)+2 种基金the Special Foundation of the Shanghai Education Commission for Nano-Materials Research, China (0852nm01400)the Crucial Project of the Shanghai Science and Technology Commission, China (08520513400)the Shanghai Leading Academic Discipline Project, China (J51402)
文摘Titanium-based composite coatings with and without Y particles were deposited by laser cladding on Ti6Al4V substrates. Solidification microstructure,phase constituents and distribution of the reinforcements with different morphologies,were investigated by X-ray diffractometer （XRD）,scanning electron microscopy （SEM） and electron probe micro analyzer （EPMA）. In addition,the effects of the addition of Y on mechanical properties （in terms of microhardness and the cracking susceptibility） were also highlighted. The results showed that the coatings were composed of α-Ti cellular dendrites,coarse needle-shaped TiB phase and an eutectic in which a large number of needle-shaped TiB whiskers and a few equiaxial TiC particles were uniformly embedded. Y was not stable and was transformed into Y2O3 during laser cladding. The addition of Y could refine the microstructure of the coating by hastening the spheroidization of primary phase structure. Moreover,it could also decrease the activity of carbon and prevent solute atoms from traversing the interface and moving into primary phase structure,namely,increase the fraction volume of TiC in the coating. All of there factors made the cracking susceptibility of the coating containing Y reduced on the premise that microhardness of the coating was increased. Microhardness of the coating without Y ranged from HV 875.6 to HV 659.8,the average microhardness was about HV 747.9. For the coating with Y,microhardness changed from HV 876.5 to HV 741.5 and the average michardness was about HV 795.3. Fracture toughness of the upper,middle,bottom and interface of the coating without Y were 6.33,8.91,11.94 and 11.93 MPa.m1/2. Fracture toughness of the similar positions of the coating with Y were 8.58,12.93,13.81,17.11 MPa.m1/2,respectively. The coating with Y presented higher microhardness and fracture toughness in comparison with that without Y. Obviously,the addition of Y had a very positive effect on the microstructure and mechanical properties of the coatings.
基金National Natural Science Foundation of China(Grant No.51975123)Fujian Provincial Natural Science Foundation of China(Grant No.2020J05115)+1 种基金Fuzhou Municipal Science and Technology Plan Project of China(Grant No.2020-PT-148)Quanzhou Municipal Science and Technology Plan Project of China(Grant No.2020C043R).
文摘Laser cladding is a new surface repair method that can improve the wear and corrosion resistance of substrate surfaces.However,the cladding layer typically exhibits a rough surface,high hardness and large residual tensile stress,and thus requires further machining and finishing.Ultrasonic rolling(U-rolling)is a highly efficient finishing and strengthening process that combines ultrasonic technology with traditional rolling(T-rolling).In this study,an ironbased alloy was coated onto the surface of H13 die steel using laser cladding,and the surface of the cladding layer was polished using U-rolling.The effects of U-rolling on the surface quality,corrosion resistance and friction and wear properties of the laser-cladding layer were investigated and compared with those obtained by T-rolling.The surface roughness of the U-rolled sample was only 1/4 that of the T-rolled sample.The hardness and residual compressive stress of the laser cladding layer after U-rolling were higher than those after T-rolling.Similarly,the surface corrosion resistance of the laser cladding layer after U-rolling was higher than that after T-rolling.U-rolling changed the surface roughness,grain size,and residual stress of the material and thus affected the corrosion resistance of the laser cladding layer.The friction coefficient and wear rate of the U-rolled surface of the cladding layer were lower than those of the T-rolled surface.In addition,the tribological properties of the cladding layer were found to be related to the rolling direction.When the friction direction of the sample was the same as the rolling direction,its friction and wear performance were higher than those when the two directions were perpendicular.
基金the National Natural Science Foundation of China (No. 51002093)the Shanghai Science and Technology Development Foundation, China (No. 08QA14035)the Shanghai Leading Academic Discipline Project, China (No. J51402)
文摘A titanium-based composite coating reinforced by in situ synthesized TiB and TiC particles was fabricated on Ti6A14V by laser cladding. The microstructure and mechanical properties were investigated. The coating was mainly composed of a-Ti cellular dendrites and an eutectic in which a large number of rod/ needle-shaped TiB and a few equiaxial TiC particles were homogeneously embedded. The microstructural evolution could be divided into four stages： precipitation and growth of primary fl-Ti phase, formation of the binary eutectic fl-Ti＋TiB, formation of the ternary eutectic fl-Ti＋TiB＋TiC, and solid transformation from fl-Ti to a-Ti. Microhardness of the coating showed a gradient variation from the surface （about HV0.2 876） to the bottom （about HV0.2 660） and was prominently improved in comparison with that of the substrate. Fracture toughness of the coating also exhibited a gradient variation from the surface （6.3 MPa-m1/2） to the interface （11.9 MPa-mV2）. Wear resistance of the coating was significantly superior to that of Ti6A14V.
文摘The latest progress and research status of laser cladding ceramic coating was summarized. Technique characteristics and influence factors of laser cladding technique were introduced. Laser cladding technique includes the mixing method and laser irradiation. The mixing method can be classified as pre-coating method and synchronization method. The technique parameters include size of facula, scanning speed, cladding sector and times, adding quantity of powder, thickness of coating and quantity of joint coating. The results show that proper technique parameters can be controlled in order to acquire high quality laser cladding coating. Strengthened effect mechanism of rare earth additive is concluded, and the main effects of rare earth additive are micro-alloying, purifying boundary, fining crystal grains, improving crystal boundary, restraining columnar crystal growing. The development of laser cladding ceramic coating research was discussed.
基金supported by the National Natural Science Foun-dation of China(grant Nos.52275318 and 52175307)Taishan Scholars Foundation of Shandong Province(No.tsqn201812128)+1 种基金Shandong Natural Science Foundation(Nos.ZR2023JQ021 and ZR2023QE221)China Academy of Space Technology Innovation Foundation(No.CAST2022).
文摘A bonding approach based on laser surface modification was developed to address the poor bonding be-tween Si_(3)N_(4) ceramic and Cu.The bonding mechanism in Si_(3)N_(4)/Cu heterogeneous composite structure fabricated by laser modification-assisted bonding is examined by means of scanning/transmission elec-tron microscopy and thermodynamic analysis.In the bonding process under laser modification,atomic intermixing at the interface is confirmed,as a result of the enhanced diffusion assisted by the dissocia-tion of Si_(3)N_(4) ceramic by laser.The dissociating Si precipitations on the surface,as well as the formation of micro-pores interfacial structure,would be the key concept of the bonding,by which the seamless and robust heterointerfaces were created.By controlling the laser-modifying conditions,we can obtain a reli-able heterostructure via the optimization of the trade-off of the surface structure and bonding strength,as determined by the laser-modified surface prior to bonding.The maximum structure depth and S ratio at the Si_(3)N_(4) surface were produced at a laser power of 56 W,corresponding to the maximal shear strength of 15.26 MPa.It is believed that the further development of this bonding technology will advance power electronic substrate fabrication applied in high-power devices.
基金Pay Jun Liew and Ching Yee Yap acknowledge the supportsfrom Universiti Teknikal Malaysia Melaka (UTeM) for thetechnical and financial supports through the grant PJP/2018/FKP(6A)/S01587.
文摘Hard coatings are extensively required in industry for protecting mechanical/structural parts that withstand extremely high temperature,stress,chemical corrosion,and other hostile environments.Electrical discharge coating(EDC)is an emerging surface modification technology to produce such hard coatings by using electrical discharges to coat a layer of material on workpiece surface to modify and enhance the surface characteristics or create new surface functions.This paper presents a comprehensive overview of EDC technologies for various materials,and summarises the types and key parameters of EDC processes as well as the characteristics of resulting coatings.It provides a systematic summary of the fundamentals and key features of the EDC processes,as well as its applications and future trends.
基金Item Sponsored by National Natural Science Foundation of China(51275006,51274016)Natural Science Foundation of Beijing of China(2142009)Scientific Plan Item of Beijing Education Committee of China(PXM2015-014204-500170)
文摘（Ti, Nb）C reinforced Fe based laser coatings were prepared with normal and high scanning velocities of the laser beam. The distribution characteristics of reinforced particles in the coatings were investigated. The mechanical properties of coatings were tested. The results showed that the morphologies of the microstructure and the reinforced particle changed dramatically at high solidification rate due to rapid laser processing compared with that prepared by normal processing. Two kinds of particles were observed in the coating. One was （Ti, Nb）C multiple carbide particle with the size of micron and sub micron scales, in which a mass of dislocations were found. Another was nano sized particle including a Fe and （Ti, Nb）C obtained by rapid solidification. The microstructure of the coatings was highly refined and a large number of twin crystals were found in matrix. The resuhs of mechanical properties test revealed that the wear resistance of the coaling was improved by rapid laser processing, compared with that of the coating prepared with normal speeds. The ahove-mentioned conclusion indicated that rapid laser cladding can promote not on ly the processing efficiency but also lhe mechanical properties of the coating.
