Co-based alloy coating was prepared on Zr alloy using laser melting and cladding technique to study the difference in the high-temperature oxidation behavior between pure metal Co coatings and Co-T800 alloy coatings,a...Co-based alloy coating was prepared on Zr alloy using laser melting and cladding technique to study the difference in the high-temperature oxidation behavior between pure metal Co coatings and Co-T800 alloy coatings,as well as the wear resistance of the coatings.Besides,the effect of changing the laser melting process on the coatings was also investigated.The oxidation mass gain at 800–1200℃and the high-temperature oxidation behavior during high-temperature treatment for 1 h of two coated Zr alloy samples were studied.Results show that the Co coating and the Co-T800 coating have better resistance against high-temperature oxidation.After oxidizing at 1000℃for 1 h,the thickness of the oxide layer of the uncoated sample was 241.0μm,whereas that of the sample with Co-based coating is only 11.8–35.5μm.The friction wear test shows that the depth of the abrasion mark of the coated sample is only 1/2 of that of the substrate,indicating that the hardness and wear resistance of the Zr substrate are greatly improved.The disadvantage of Co-based coatings is the inferior corrosion resistance in 3.5wt%NaCl solution.展开更多
Transition metal-based nanomaterials have emerged as promising electrocatalysts for oxygen evolution reaction(OER).Considerable research efforts have shown that self-reconstruction occurs on these nanomaterials under ...Transition metal-based nanomaterials have emerged as promising electrocatalysts for oxygen evolution reaction(OER).Considerable research efforts have shown that self-reconstruction occurs on these nanomaterials under operating conditions of OER process.However,most of them undergo incomplete reconstruction with limited thickness of reconstruction layer,leading to low component utilization and arduous exploration of real catalytic mechanism.Herein,we identify the dynamic behaviors in complete reconstruction of Co-based complexes during OER.The hollow phytic acid(PA)cross-linked CoFe-based complex nanoboxes with porous nanowalls are designed because of their good electrolyte penetration and mass transport ability,in favor of the fast and complete reconstruction.A series of experiment characterizations demonstrate that the reconstruction process includes the fast substitution of PA by OH-to form Co(Fe)(OH)xand subsequent potential-driven oxidation to Co(Fe)OOH.The obtained CoFeOOH delivers a low overpotential of 290 mV at a current density of 10 mA cm^(-2)and a long-term stability.The experiment results together with theory calculations reveal that the Fe incorporation can result in the electron rearrangement of reconstructed CoFeOOH and optimization of their electronic structure,accounting for the enhanced OER activity.The work provides new insights into complete reconstruction of metal-based complexes during OER and offers guidelines for rational design of high-performance electrocatalysts.展开更多
To explain the precipitation mechanism ofχphase in Co-based superalloys,the microstructural evolution of Co−Ti−Mo superalloys subjected to aging was investigated by X-ray diffraction(XRD),scanning electron microscope...To explain the precipitation mechanism ofχphase in Co-based superalloys,the microstructural evolution of Co−Ti−Mo superalloys subjected to aging was investigated by X-ray diffraction(XRD),scanning electron microscope(SEM)and transmission electron microscope(TEM).The results show that the needle-likeχphase is mainly composed ofD0_(19)-Co_(3)(Ti,Mo),which is transformed from L1_(2-γ′)phase,and a specific orientation relationship exists between them.χphase is nucleated through the shearing ofγ′phase due to the influence of stacking fault.The crystal orientation relationship between L1_(2) andD0_(19)can be confirmed as{111}L1_(2)//{0001}_(D0_(19)),and<112>_(L1_(2))//<1100>_(D0_(19)).The growth ofD0_(19-χ)phase depends on the diffusions of Ti and Mo,and consumes a large number of elements.This progress leads to the appearance ofγ′precipitation depletion zone(PDZ)aroundD0_(19-χ)phase.The addition of Ni improves the stability of L1_(2-γ′)phase and the mechanical properties of Co-based superalloys.展开更多
To date,Co-based metal-organic frameworks(Co-MOFs)have drawn much attention owing to their advantages of easy preparation,high porosity and adjustable structure.Because of these enticing properties,numerous efforts ha...To date,Co-based metal-organic frameworks(Co-MOFs)have drawn much attention owing to their advantages of easy preparation,high porosity and adjustable structure.Because of these enticing properties,numerous efforts have been devoted to their applications in energy storage and conversion.However,poor conductivity has become one of the biggest obstacles for large-scale use of pristine Co-MOFs.Subsequently,many attempts have been carried out to develop various Co-MOF derived materials as electrodes for rechargeable batteries in order to address the above-mentioned shortcoming and to enhance the electrical conductivity with improved stability during cycling.Moreover,in addition to improvement of Li-ion batteries in practical utilization,seeking for other rechargeable batteries is another urgent task due to the high cost and limited sources of metallic Li.Herein,by following the recent research progress,this review provides an overview of applications of Co-MOF derived materials in various rechargeable batteries including lithium-ion batteries,sodium-ion batteries,lithium-sulfur batteries,zinc air batteries and other rechargeable batteries,where they have been utilized as cathodes,anodes,separators and electrocatalysts.Accordingly,we categorize and compare the morphology driven electrochemical performance of various Co-MOF derivatives including porous carbon,cobalt oxides,cobalt chalcogenides,cobalt phosphides and corresponding composites.Finally,current challenges for large-scale production and commercialization of Co-MOF derived materials as well as some reasonable solutions have been discussed at the end.展开更多
The structure of the yttrium modified Co-base alloy layers formed by laser cladding on 2Cr13 and 1Cr18Ni9Ti steel surfaces and its hot corrosion performance have been investigated systematically.The re- sults show tha...The structure of the yttrium modified Co-base alloy layers formed by laser cladding on 2Cr13 and 1Cr18Ni9Ti steel surfaces and its hot corrosion performance have been investigated systematically.The re- sults show that the Y-containing cobalt base clad alloy has a finer microstructure and higher corrosion re- sistance to the salt mixture of 75% Na_2SO_4+25%NaCl at high temperature.The unique properties are ob- tained with addition of 0.875% Y for the formation of a continuous and compact oxide scale.The compact scale may act as a barrier for the inward diffusion of oxygen and sulphur and also for the outward diffusion of alloying elements.展开更多
Post-bond heat treatment(PBHT) applied to a transient liquid phase(TLP) bonding joint is an effective approach to remove the brittle borides and improve its properties.Herein,we proposed two types of PBHT strategies t...Post-bond heat treatment(PBHT) applied to a transient liquid phase(TLP) bonding joint is an effective approach to remove the brittle borides and improve its properties.Herein,we proposed two types of PBHT strategies to obtain a TLP bonded γ'-strengthened Co-based single crystal superalloy,and the microstructural characteristics and tensile properties of the two heat treated joints were compared to identify the optimal PBHT strategy.The evolution of the brittle boride in the joint after the PBHT was studied by using in-situ microscopy.The experimental results allowed to provide a theoretic model to quantitatively evaluate the distribution of the brittle phase after the optimal PBHT and analyze the joint fractures to understand the failure mechanisms.The obtained results revealed that a post-bond solid solution treatment performed to the joint at a high temperature(over 1275℃) could decrease the area fraction of the boride from 7.2 % to 1.4 % and increase the elongation from 1.9 % to 7.8 %.This work emphasizes the relevance of solid solution temperature when a PBHT strategy is applied.展开更多
Fe-based and Co-based cladding layers were prepared on the surface of AISI H13 hot die steel by laser cladding technology.The microstructure,hardness and abrasion resistance of the two cladding layers were studied by ...Fe-based and Co-based cladding layers were prepared on the surface of AISI H13 hot die steel by laser cladding technology.The microstructure,hardness and abrasion resistance of the two cladding layers were studied by means of optical microscope,scanning electron microscope,rockwell hardness tester,and high temperature friction and wear tester.Also,the red hardness of the cladding layers was measured,after holding the layers at 600℃ for 1 hour by muffle furnace and repeated 4 times.The rockwell hardness values of the substrate,the Fe-based and the Co-based alloy coating measured were HRC 47,HRC 52 and HRC 48,respectively.The red hardness values of the substrate and the Fe-based cladding layer were decreased,while that of the Co-based cladding layer was increased.The Co-based cladding layer has the minimal wear loss weight and friction coefficient among them.The wear mechanisms of the substrate,the Fe-based layer and the Cobased layer attribute mainly to abrasive wear,adhesion wear,and both of them,respectively.展开更多
Ni-base alloy DZ468 has been joined by transient liquid phase bonding technique with a newly developed Co-based filler. The microstructures of the Co-base filler and the joint, the effects of heat treatment on microst...Ni-base alloy DZ468 has been joined by transient liquid phase bonding technique with a newly developed Co-based filler. The microstructures of the Co-base filler and the joint, the effects of heat treatment on microstructure and hardness of the joint have been investigated by various experimental methods. Results show that the Co-base filler consists of γ, M2B, M5B3 and M23B6 phases. Because of the interdiffusion between the base metal and the filler, γ, MC, M5B3 and M23B6 phases are formed in the bonding zone. And localized liquidation of substrate occurs in the diffusion affected zone, with MC and M3B2 precipitating in this area. During heat treatment, the volume of the intermetallic phases in the bonding zone resulting from incomplete isothermal solidification decreases obviously. On the contrary, the width of the diffusion affected zone increases at the solution stage and subsequently decreases at the aging stages.展开更多
In this work,the microstructural evolution,micro-crack formation,and mechanical anisotropy of the selective laser melted(SLM)carbon-free Mar-M509 Co-based superalloy were systematically studied under different linear ...In this work,the microstructural evolution,micro-crack formation,and mechanical anisotropy of the selective laser melted(SLM)carbon-free Mar-M509 Co-based superalloy were systematically studied under different linear energy densities(LED).Observation shows that the SLM Mar-M509 superalloy possesses a fully dense structure,whereas some microcracks exist along the building direction.The electron backscatter diffraction results reveal that dominant columnar grains tend to elongate along the building direction parallel to the XZ plane.Meanwhile,both a<001>near fiber texture and a{100}<001>near sheet texture are observed in different specimens.For the specimen with fiber texture,a high misorientation angle exists among different columnar grains,which aggravated the generation of micro-cracks under thermal stress.Higher LED results in higher micro-crack density in the SLM specimen due to higher thermal stress.Mar-M509 specimen fabricated under lower LED exhibits higher tensile strength due to more significant grain refinement.More prominent anisotropy of tensile performance was found in the high LED specimen,which can be attributed to the higher density of micro-cracks and crystallographic texture.Furthermore,the SLM Mar-M509 superalloy exhibits better mechanical properties than the traditional cast technique.In summary,this work can contribute to the development and the future application of SLM-fabricated Co-based superalloy.展开更多
The macroscopically localized deformation behaviors of Ni–Co-based superalloys with differentγ’precipitate content were investigated at 500?C and 1×10-4 s-1 via an in situ method namely,digital image correlati...The macroscopically localized deformation behaviors of Ni–Co-based superalloys with differentγ’precipitate content were investigated at 500?C and 1×10-4 s-1 via an in situ method namely,digital image correlation(DIC).The DIC results showed that the serrated flow of the stress–strain curves was accompanied by localized deformation of the specimens.The fracture morphology was characterized mainly by transgranular fracture with numerous dimples in the lowγ’content alloy,and intergranular fracture with large fracture section in the highγ’content alloy.The Portevin–Le Chatelier(PLC)effect occurred in the investigated Ni–Co-based superalloys.Furthermore,the localized deformation of the highγ’content alloy was more severe than that of the lowγ’content alloy,and the band width was slightly larger.Moreover,for the first-time ever,a special propagation feature,namely±60?zigzag bands characterized by head-to-tail connections,was observed in the highγ’content alloy.展开更多
The Co-based alloy coatings had been prepared by laser cladding and vacuum fusion sintering. Microstructures of the coatings were investigated and the performance of thermal cycling was also tested using scanning elec...The Co-based alloy coatings had been prepared by laser cladding and vacuum fusion sintering. Microstructures of the coatings were investigated and the performance of thermal cycling was also tested using scanning electron microscopy （ SEM） and X-ray diffraction （ XRD ）. The results show that the coatings and substrates combine well. The main phase compositions of laser cladding coating are T-Co, Cr23 C6 and Ni2 9 Cro. 7 Feo. 36, while vacuum fusion sintering coating consists of Co, Cr7 C3, and Ni2.9 Cro. 7 Feo. 36. After thermal cycling, the minimum hot cracking width of laser cladding coating is 14 μm; moreover, laser cladding coating maintains high hardness and hot-cracking susceptibility. Those are beneficial to high temperature wear resistance of hot work dies.展开更多
A thermal fatigue behaviour of Co-based alloy coating obtained by laser surface meltcasting on the high temperature alloy GH33 was studied.The results show that after each time of thermal cycling,the final residual st...A thermal fatigue behaviour of Co-based alloy coating obtained by laser surface meltcasting on the high temperature alloy GH33 was studied.The results show that after each time of thermal cycling,the final residual stress was formed in the melt-casting layer which is attributed to the thermal stress and structural stress.Through the first 50 times of thermal cycling,the morphology of coating still inherits the laser casting one,but the dendrites get bigger;After the second 50 times of thermal cycling,corrosion pits emerge from coating,and mostly in the places where coating and substrate meet.The fatigue damage type of coating belongs to stress corrosion.展开更多
Co-based superalloy coating was prepared on the stainless steel surface by laser cladding.The microstructure,phase constitutes and worn surface morphology of the coating were characterized by optical microscope,scanni...Co-based superalloy coating was prepared on the stainless steel surface by laser cladding.The microstructure,phase constitutes and worn surface morphology of the coating were characterized by optical microscope,scanning electron microscope(SEM)with energy dispersive spectrum(EDS)and X-ray diffraction(XRD).The ambient temperature sliding friction and wear property of the coating was also tested.The experiments results showed that:the microstructures of the Co-based superalloy coating are"cellular crystal-coarse dendrite-tiny dendrite"in turn from bottom to surface,which consists ofγ-Co solid solution,Fe2Mo and Co7Mo6.The average micro-hardness of the laser cladding is 632 HV,which is 2 times higher than that of 304 stainless steel matrix.The ambient temperature sliding friction and wear property of the laser cladding is about 1～1.5 times in contrast to that of 304 stainless steel matrix.The better wear resistance of the coating is contributed to solution strengthening of Mo,as well as dispersion strengthening of Fe2Mo and Co7Mo6 hard phases.The failure mechanisms of the coating are pitting fatigue abrasion and grain-abrasion.展开更多
The oxidation behavior of a cast polycrystalline Co-base superalloy was studied at temperatures from 900 to 1050℃ and analyzed by thermogravimetric analysis （TGA）, X-ray diffraction （XRD） and scanning electron mi...The oxidation behavior of a cast polycrystalline Co-base superalloy was studied at temperatures from 900 to 1050℃ and analyzed by thermogravimetric analysis （TGA）, X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results indicate that a cast Co-base superalloy follows the subparabolic oxidation kinetics at 900 and 1000℃, which are controlled by the growth of the inner Cr-rich layer, and that after oxidation at 1050℃ for 200 h, it almost exhibits the linear oxidation kinetics possible due to the volatility of Cr-rich oxide. A mixed scale forms on the alloy after prolonged oxidation. The oxide scale formed at 900 and 1000℃ is composed of an outer layer of spinel and an inner continuous Cr-rich layer and at I050℃ is composed of a very discontinuous Cr-rich layer.展开更多
The effect of La element on the mechanical properties and constitution nearby grain boundary in a Co-base superalloy Co-22Ni-22Cr-14k during 760℃ ageing has been investigated by AES and material testing. Results show...The effect of La element on the mechanical properties and constitution nearby grain boundary in a Co-base superalloy Co-22Ni-22Cr-14k during 760℃ ageing has been investigated by AES and material testing. Results show that element La can be in a state of solid solution and segregates mainly at the vicinity of grain boundaries. The prior segregation of La atoms can affect segregation behaviour of other elements, so that exerts influence on microstructure of the alloy, Particularly increasing of La content can decrease P concentration at the vicinity of grain boundaries but not decrease S concentration. S together with La produce cosegregation effect. The content of La has no obvious effect on high temperature strength. When the content of La comes up to 0.02wt-％, it can obviously improve the high temperature ductility.展开更多
Co-base refractory alloy coating was prepared on carbon steel substrate by cold spray technology; microstructure and nano-mechenieal property were examined by scanning electron microscope （SEM） and nano indenter ind...Co-base refractory alloy coating was prepared on carbon steel substrate by cold spray technology; microstructure and nano-mechenieal property were examined by scanning electron microscope （SEM） and nano indenter individually. The results showed that about 250 μm Co-base refractory alloy coating could be deposited o11 steel substrate by cold spray technique, interface between coating and substrate was combined well, and the refractory alloy particle had a significant plastic deformation during deposition process; mixing Ni powders into Co-base refractory alloy powders could increase the density and decrease the nano-hardness of coating, the nano-hardness and elastic modulus of refractory alloy coating was higher than 6 GPa and 160 GPa, respectively.展开更多
Co-based superalloys such as FSX-414 have been recently used in gas turbine first stage nozzles. During service, nozzles are exposed to low cycle fatigue, which can lead to cracking of these components. The cracks on ...Co-based superalloys such as FSX-414 have been recently used in gas turbine first stage nozzles. During service, nozzles are exposed to low cycle fatigue, which can lead to cracking of these components. The cracks on these nozzles are usually welded with ttmgsten arc welding （TIG） using Co-based filler metals. In this paper, the effect of TIG on the tensile and low cycle fatigue properties of Co-based superalloy FSX-414 was studied at 950℃. The experimental results show that the yield and ultimate tensile stresses of welded and unwelded specimens are comparable to each other. But toughness of welded specimens is lower than that of unwelded ones. The low cycle fatigue properties of FSX-414 were studied at a strain rate of 3.3×10^-4 s^-1, strain ratio R=-1 （R=emin/emax） and Aet （total strain change） from 0.8% to 2%. In welded specimens, at high strain cycling, the nucleation and growth of cracks occur in the welded zone. But at Aet=0.8%, fracture occurs in the same zones of unwelded specimens. The results show that the total fatigue lives of the welded specimens are shorter than those of unwelded ones. In all of the low cycle fatigue tests, softening phenomena are observed.展开更多
The effect of trace element B on microstructure of directionally solidified new type Co-base superalloy is studied systematically in this paper. It is found that the addition of B makes the incipient melting temperatu...The effect of trace element B on microstructure of directionally solidified new type Co-base superalloy is studied systematically in this paper. It is found that the addition of B makes the incipient melting temperature of the alloy decline remarkably. Compared with the alloy having a boron content of 0.05 %, the incipient melting temperature of the alloy with 0.7 % B decreases by 197℃. The primary and secondary dendrite arm spacings increase and the volume fraction of interdendritic carbides with fine microstructure becomes bigger with the enhancement of boron content. When the alloy is with 0.7wt %B, M3B2 precipitates in the interdendrites.展开更多
Layered Co-based ceramics with a nominal composition Bi2-xLaxSr2Co2O8-δ (x=0.0, 0.4, 0.8, short by BLC-222) were prepared using conventional solid state reaction method. X-ray photoemission spectroscopy (XPS) was use...Layered Co-based ceramics with a nominal composition Bi2-xLaxSr2Co2O8-δ (x=0.0, 0.4, 0.8, short by BLC-222) were prepared using conventional solid state reaction method. X-ray photoemission spectroscopy (XPS) was used to investigate their electronic structures. The cobalt ions are highly mixed valences of Co3+ and Co4+. The fraction of Co4+ almost keeps unchanged with the increase of x. The O-1s photoemission spectra show that there are lattice oxygen and chemical absorbed oxygen in all the samples. The substitution of Bi3+ by La3+ results in a change from metallic-like behavior to semiconductor behavior. This abnormal phenomenon means that La3+ plays a key role in effecting the electrical transport property of BLC-222. The O-Co covalence bond is strengthened by the increase of La3+, which results in the decrease of conductivity.展开更多
High levels of Al and Ti in superalloy compositions normally lead to cracking formation during the laser powder bed fusion process,while these elements are key constituents of strengthening phases.In the current study...High levels of Al and Ti in superalloy compositions normally lead to cracking formation during the laser powder bed fusion process,while these elements are key constituents of strengthening phases.In the current study,a novel Co-based superalloy with the basic chemical composition of Co-Al-W-Ta-Ti resolved this contradiction,indicating that the part was formed without cracking and simultaneously contained a large amount of strengthening precipitates in the microstructure fabricated via laser powder bed fusion.The printability,microstructures,and mechanical properties of the sample were analysed before and after heat treatment,providing a potential superalloy that can replace Ni-based superalloys fabricated by additive manufacturing in aerospace and other industries with higher temperature and more efficiency.展开更多
基金National Natural Science Foundation of China(52071126)Natural Science Foundation of Tianjin City,China(22JCQNJC01240)+2 种基金Central Guidance on Local Science and Technology Development Fund of Hebei Province(226Z1009G)Special Funds for Science and Technology Innovation in Hebei(2022X19)Anhui Provincial Natural Science Foundation(2308085ME135)。
文摘Co-based alloy coating was prepared on Zr alloy using laser melting and cladding technique to study the difference in the high-temperature oxidation behavior between pure metal Co coatings and Co-T800 alloy coatings,as well as the wear resistance of the coatings.Besides,the effect of changing the laser melting process on the coatings was also investigated.The oxidation mass gain at 800–1200℃and the high-temperature oxidation behavior during high-temperature treatment for 1 h of two coated Zr alloy samples were studied.Results show that the Co coating and the Co-T800 coating have better resistance against high-temperature oxidation.After oxidizing at 1000℃for 1 h,the thickness of the oxide layer of the uncoated sample was 241.0μm,whereas that of the sample with Co-based coating is only 11.8–35.5μm.The friction wear test shows that the depth of the abrasion mark of the coated sample is only 1/2 of that of the substrate,indicating that the hardness and wear resistance of the Zr substrate are greatly improved.The disadvantage of Co-based coatings is the inferior corrosion resistance in 3.5wt%NaCl solution.
基金National Natural Science Foundation of China(22478310,U21A20286 and 22206054)。
文摘Transition metal-based nanomaterials have emerged as promising electrocatalysts for oxygen evolution reaction(OER).Considerable research efforts have shown that self-reconstruction occurs on these nanomaterials under operating conditions of OER process.However,most of them undergo incomplete reconstruction with limited thickness of reconstruction layer,leading to low component utilization and arduous exploration of real catalytic mechanism.Herein,we identify the dynamic behaviors in complete reconstruction of Co-based complexes during OER.The hollow phytic acid(PA)cross-linked CoFe-based complex nanoboxes with porous nanowalls are designed because of their good electrolyte penetration and mass transport ability,in favor of the fast and complete reconstruction.A series of experiment characterizations demonstrate that the reconstruction process includes the fast substitution of PA by OH-to form Co(Fe)(OH)xand subsequent potential-driven oxidation to Co(Fe)OOH.The obtained CoFeOOH delivers a low overpotential of 290 mV at a current density of 10 mA cm^(-2)and a long-term stability.The experiment results together with theory calculations reveal that the Fe incorporation can result in the electron rearrangement of reconstructed CoFeOOH and optimization of their electronic structure,accounting for the enhanced OER activity.The work provides new insights into complete reconstruction of metal-based complexes during OER and offers guidelines for rational design of high-performance electrocatalysts.
基金The financial supports from the National Natural Science Foundation of China(Nos.52171107,52201203)the National Natural Science Foundation of China-Joint Fund of Iron and Steel Research(No.U1960204)the“333”Talent Project of Hebei Province,China(No.B20221001)are gratefully acknowledged.
文摘To explain the precipitation mechanism ofχphase in Co-based superalloys,the microstructural evolution of Co−Ti−Mo superalloys subjected to aging was investigated by X-ray diffraction(XRD),scanning electron microscope(SEM)and transmission electron microscope(TEM).The results show that the needle-likeχphase is mainly composed ofD0_(19)-Co_(3)(Ti,Mo),which is transformed from L1_(2-γ′)phase,and a specific orientation relationship exists between them.χphase is nucleated through the shearing ofγ′phase due to the influence of stacking fault.The crystal orientation relationship between L1_(2) andD0_(19)can be confirmed as{111}L1_(2)//{0001}_(D0_(19)),and<112>_(L1_(2))//<1100>_(D0_(19)).The growth ofD0_(19-χ)phase depends on the diffusions of Ti and Mo,and consumes a large number of elements.This progress leads to the appearance ofγ′precipitation depletion zone(PDZ)aroundD0_(19-χ)phase.The addition of Ni improves the stability of L1_(2-γ′)phase and the mechanical properties of Co-based superalloys.
基金financially supported by the Guangzhou Science and Technology Project,China(No.201904010213)the Foundation of Anhui Province Key Laboratory of Functional Coordinated Complexes for Materials Chemistry and Application(Nos.LFCCMCA-01 and LFCCMCA-06)+1 种基金the Scientific Research Launch Project of Anhui Polytechnic University(No.2020YQQ057)the Scientific Research Project of Anhui Polytechnic University(No.Xjky2020090)。
文摘To date,Co-based metal-organic frameworks(Co-MOFs)have drawn much attention owing to their advantages of easy preparation,high porosity and adjustable structure.Because of these enticing properties,numerous efforts have been devoted to their applications in energy storage and conversion.However,poor conductivity has become one of the biggest obstacles for large-scale use of pristine Co-MOFs.Subsequently,many attempts have been carried out to develop various Co-MOF derived materials as electrodes for rechargeable batteries in order to address the above-mentioned shortcoming and to enhance the electrical conductivity with improved stability during cycling.Moreover,in addition to improvement of Li-ion batteries in practical utilization,seeking for other rechargeable batteries is another urgent task due to the high cost and limited sources of metallic Li.Herein,by following the recent research progress,this review provides an overview of applications of Co-MOF derived materials in various rechargeable batteries including lithium-ion batteries,sodium-ion batteries,lithium-sulfur batteries,zinc air batteries and other rechargeable batteries,where they have been utilized as cathodes,anodes,separators and electrocatalysts.Accordingly,we categorize and compare the morphology driven electrochemical performance of various Co-MOF derivatives including porous carbon,cobalt oxides,cobalt chalcogenides,cobalt phosphides and corresponding composites.Finally,current challenges for large-scale production and commercialization of Co-MOF derived materials as well as some reasonable solutions have been discussed at the end.
基金Research Project supported by the Corrosion Science Laboratory,Academia Sinica
文摘The structure of the yttrium modified Co-base alloy layers formed by laser cladding on 2Cr13 and 1Cr18Ni9Ti steel surfaces and its hot corrosion performance have been investigated systematically.The re- sults show that the Y-containing cobalt base clad alloy has a finer microstructure and higher corrosion re- sistance to the salt mixture of 75% Na_2SO_4+25%NaCl at high temperature.The unique properties are ob- tained with addition of 0.875% Y for the formation of a continuous and compact oxide scale.The compact scale may act as a barrier for the inward diffusion of oxygen and sulphur and also for the outward diffusion of alloying elements.
基金financially supported by the Project from the National Natural Science Foundation of China under Grant(No.51771191)the National Key Research and Development Program of China under Grant(No.2017YFA0700704)the Aerospace Power Foundation under Grant(DLJJ1825)。
文摘Post-bond heat treatment(PBHT) applied to a transient liquid phase(TLP) bonding joint is an effective approach to remove the brittle borides and improve its properties.Herein,we proposed two types of PBHT strategies to obtain a TLP bonded γ'-strengthened Co-based single crystal superalloy,and the microstructural characteristics and tensile properties of the two heat treated joints were compared to identify the optimal PBHT strategy.The evolution of the brittle boride in the joint after the PBHT was studied by using in-situ microscopy.The experimental results allowed to provide a theoretic model to quantitatively evaluate the distribution of the brittle phase after the optimal PBHT and analyze the joint fractures to understand the failure mechanisms.The obtained results revealed that a post-bond solid solution treatment performed to the joint at a high temperature(over 1275℃) could decrease the area fraction of the boride from 7.2 % to 1.4 % and increase the elongation from 1.9 % to 7.8 %.This work emphasizes the relevance of solid solution temperature when a PBHT strategy is applied.
文摘Fe-based and Co-based cladding layers were prepared on the surface of AISI H13 hot die steel by laser cladding technology.The microstructure,hardness and abrasion resistance of the two cladding layers were studied by means of optical microscope,scanning electron microscope,rockwell hardness tester,and high temperature friction and wear tester.Also,the red hardness of the cladding layers was measured,after holding the layers at 600℃ for 1 hour by muffle furnace and repeated 4 times.The rockwell hardness values of the substrate,the Fe-based and the Co-based alloy coating measured were HRC 47,HRC 52 and HRC 48,respectively.The red hardness values of the substrate and the Fe-based cladding layer were decreased,while that of the Co-based cladding layer was increased.The Co-based cladding layer has the minimal wear loss weight and friction coefficient among them.The wear mechanisms of the substrate,the Fe-based layer and the Cobased layer attribute mainly to abrasive wear,adhesion wear,and both of them,respectively.
基金supported by the National Base Research Program of China
文摘Ni-base alloy DZ468 has been joined by transient liquid phase bonding technique with a newly developed Co-based filler. The microstructures of the Co-base filler and the joint, the effects of heat treatment on microstructure and hardness of the joint have been investigated by various experimental methods. Results show that the Co-base filler consists of γ, M2B, M5B3 and M23B6 phases. Because of the interdiffusion between the base metal and the filler, γ, MC, M5B3 and M23B6 phases are formed in the bonding zone. And localized liquidation of substrate occurs in the diffusion affected zone, with MC and M3B2 precipitating in this area. During heat treatment, the volume of the intermetallic phases in the bonding zone resulting from incomplete isothermal solidification decreases obviously. On the contrary, the width of the diffusion affected zone increases at the solution stage and subsequently decreases at the aging stages.
基金financially supported by the National Key Research and Development Program of China(No.2019YFA0705300)the Chinese National Science and Technology Major Project“Aeroengine and Gas Turbine”(No.2017-VII0008-0102)+4 种基金the Shanghai Science and Technology Committee(No.19DZ1100704)Shanghai Shuguang Program(No.20SG42)Shanghai Sailing Program(No.19YF1415900)the National Natural Science Foundation of China(No.52001191)the Shanghai Rising-Star Program(No.20QA1403800)。
文摘In this work,the microstructural evolution,micro-crack formation,and mechanical anisotropy of the selective laser melted(SLM)carbon-free Mar-M509 Co-based superalloy were systematically studied under different linear energy densities(LED).Observation shows that the SLM Mar-M509 superalloy possesses a fully dense structure,whereas some microcracks exist along the building direction.The electron backscatter diffraction results reveal that dominant columnar grains tend to elongate along the building direction parallel to the XZ plane.Meanwhile,both a<001>near fiber texture and a{100}<001>near sheet texture are observed in different specimens.For the specimen with fiber texture,a high misorientation angle exists among different columnar grains,which aggravated the generation of micro-cracks under thermal stress.Higher LED results in higher micro-crack density in the SLM specimen due to higher thermal stress.Mar-M509 specimen fabricated under lower LED exhibits higher tensile strength due to more significant grain refinement.More prominent anisotropy of tensile performance was found in the high LED specimen,which can be attributed to the higher density of micro-cracks and crystallographic texture.Furthermore,the SLM Mar-M509 superalloy exhibits better mechanical properties than the traditional cast technique.In summary,this work can contribute to the development and the future application of SLM-fabricated Co-based superalloy.
基金supported by the National Natural Science Foundation of China(Grant Nos.11335010,51271174,11802080 and 11627803)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB22040502)。
文摘The macroscopically localized deformation behaviors of Ni–Co-based superalloys with differentγ’precipitate content were investigated at 500?C and 1×10-4 s-1 via an in situ method namely,digital image correlation(DIC).The DIC results showed that the serrated flow of the stress–strain curves was accompanied by localized deformation of the specimens.The fracture morphology was characterized mainly by transgranular fracture with numerous dimples in the lowγ’content alloy,and intergranular fracture with large fracture section in the highγ’content alloy.The Portevin–Le Chatelier(PLC)effect occurred in the investigated Ni–Co-based superalloys.Furthermore,the localized deformation of the highγ’content alloy was more severe than that of the lowγ’content alloy,and the band width was slightly larger.Moreover,for the first-time ever,a special propagation feature,namely±60?zigzag bands characterized by head-to-tail connections,was observed in the highγ’content alloy.
文摘The Co-based alloy coatings had been prepared by laser cladding and vacuum fusion sintering. Microstructures of the coatings were investigated and the performance of thermal cycling was also tested using scanning electron microscopy （ SEM） and X-ray diffraction （ XRD ）. The results show that the coatings and substrates combine well. The main phase compositions of laser cladding coating are T-Co, Cr23 C6 and Ni2 9 Cro. 7 Feo. 36, while vacuum fusion sintering coating consists of Co, Cr7 C3, and Ni2.9 Cro. 7 Feo. 36. After thermal cycling, the minimum hot cracking width of laser cladding coating is 14 μm; moreover, laser cladding coating maintains high hardness and hot-cracking susceptibility. Those are beneficial to high temperature wear resistance of hot work dies.
基金Project Sponsored by Committee on Science and Technology of Guizhou Province(943068)
文摘A thermal fatigue behaviour of Co-based alloy coating obtained by laser surface meltcasting on the high temperature alloy GH33 was studied.The results show that after each time of thermal cycling,the final residual stress was formed in the melt-casting layer which is attributed to the thermal stress and structural stress.Through the first 50 times of thermal cycling,the morphology of coating still inherits the laser casting one,but the dendrites get bigger;After the second 50 times of thermal cycling,corrosion pits emerge from coating,and mostly in the places where coating and substrate meet.The fatigue damage type of coating belongs to stress corrosion.
文摘Co-based superalloy coating was prepared on the stainless steel surface by laser cladding.The microstructure,phase constitutes and worn surface morphology of the coating were characterized by optical microscope,scanning electron microscope(SEM)with energy dispersive spectrum(EDS)and X-ray diffraction(XRD).The ambient temperature sliding friction and wear property of the coating was also tested.The experiments results showed that:the microstructures of the Co-based superalloy coating are"cellular crystal-coarse dendrite-tiny dendrite"in turn from bottom to surface,which consists ofγ-Co solid solution,Fe2Mo and Co7Mo6.The average micro-hardness of the laser cladding is 632 HV,which is 2 times higher than that of 304 stainless steel matrix.The ambient temperature sliding friction and wear property of the laser cladding is about 1～1.5 times in contrast to that of 304 stainless steel matrix.The better wear resistance of the coating is contributed to solution strengthening of Mo,as well as dispersion strengthening of Fe2Mo and Co7Mo6 hard phases.The failure mechanisms of the coating are pitting fatigue abrasion and grain-abrasion.
基金supported by the National Natural Science Foundation of China under Grant No.50501024.
文摘The oxidation behavior of a cast polycrystalline Co-base superalloy was studied at temperatures from 900 to 1050℃ and analyzed by thermogravimetric analysis （TGA）, X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results indicate that a cast Co-base superalloy follows the subparabolic oxidation kinetics at 900 and 1000℃, which are controlled by the growth of the inner Cr-rich layer, and that after oxidation at 1050℃ for 200 h, it almost exhibits the linear oxidation kinetics possible due to the volatility of Cr-rich oxide. A mixed scale forms on the alloy after prolonged oxidation. The oxide scale formed at 900 and 1000℃ is composed of an outer layer of spinel and an inner continuous Cr-rich layer and at I050℃ is composed of a very discontinuous Cr-rich layer.
文摘The effect of La element on the mechanical properties and constitution nearby grain boundary in a Co-base superalloy Co-22Ni-22Cr-14k during 760℃ ageing has been investigated by AES and material testing. Results show that element La can be in a state of solid solution and segregates mainly at the vicinity of grain boundaries. The prior segregation of La atoms can affect segregation behaviour of other elements, so that exerts influence on microstructure of the alloy, Particularly increasing of La content can decrease P concentration at the vicinity of grain boundaries but not decrease S concentration. S together with La produce cosegregation effect. The content of La has no obvious effect on high temperature strength. When the content of La comes up to 0.02wt-％, it can obviously improve the high temperature ductility.
文摘Co-base refractory alloy coating was prepared on carbon steel substrate by cold spray technology; microstructure and nano-mechenieal property were examined by scanning electron microscope （SEM） and nano indenter individually. The results showed that about 250 μm Co-base refractory alloy coating could be deposited o11 steel substrate by cold spray technique, interface between coating and substrate was combined well, and the refractory alloy particle had a significant plastic deformation during deposition process; mixing Ni powders into Co-base refractory alloy powders could increase the density and decrease the nano-hardness of coating, the nano-hardness and elastic modulus of refractory alloy coating was higher than 6 GPa and 160 GPa, respectively.
文摘Co-based superalloys such as FSX-414 have been recently used in gas turbine first stage nozzles. During service, nozzles are exposed to low cycle fatigue, which can lead to cracking of these components. The cracks on these nozzles are usually welded with ttmgsten arc welding （TIG） using Co-based filler metals. In this paper, the effect of TIG on the tensile and low cycle fatigue properties of Co-based superalloy FSX-414 was studied at 950℃. The experimental results show that the yield and ultimate tensile stresses of welded and unwelded specimens are comparable to each other. But toughness of welded specimens is lower than that of unwelded ones. The low cycle fatigue properties of FSX-414 were studied at a strain rate of 3.3×10^-4 s^-1, strain ratio R=-1 （R=emin/emax） and Aet （total strain change） from 0.8% to 2%. In welded specimens, at high strain cycling, the nucleation and growth of cracks occur in the welded zone. But at Aet=0.8%, fracture occurs in the same zones of unwelded specimens. The results show that the total fatigue lives of the welded specimens are shorter than those of unwelded ones. In all of the low cycle fatigue tests, softening phenomena are observed.
文摘The effect of trace element B on microstructure of directionally solidified new type Co-base superalloy is studied systematically in this paper. It is found that the addition of B makes the incipient melting temperature of the alloy decline remarkably. Compared with the alloy having a boron content of 0.05 %, the incipient melting temperature of the alloy with 0.7 % B decreases by 197℃. The primary and secondary dendrite arm spacings increase and the volume fraction of interdendritic carbides with fine microstructure becomes bigger with the enhancement of boron content. When the alloy is with 0.7wt %B, M3B2 precipitates in the interdendrites.
基金the National Nature Science Foundation of China (20571019)the Project-sponsored by SRF for ROCS ,HLJ (LC06C13)+1 种基金Project-Sponsored by Program of Harbin Subject Chief Scientist (2006RFXXG001)Development Programfor Outstanding Young Teachers in Harbin Institute of Technology (HITQNJS.2006.028)
文摘Layered Co-based ceramics with a nominal composition Bi2-xLaxSr2Co2O8-δ (x=0.0, 0.4, 0.8, short by BLC-222) were prepared using conventional solid state reaction method. X-ray photoemission spectroscopy (XPS) was used to investigate their electronic structures. The cobalt ions are highly mixed valences of Co3+ and Co4+. The fraction of Co4+ almost keeps unchanged with the increase of x. The O-1s photoemission spectra show that there are lattice oxygen and chemical absorbed oxygen in all the samples. The substitution of Bi3+ by La3+ results in a change from metallic-like behavior to semiconductor behavior. This abnormal phenomenon means that La3+ plays a key role in effecting the electrical transport property of BLC-222. The O-Co covalence bond is strengthened by the increase of La3+, which results in the decrease of conductivity.
基金supported by the Shenzhen-Hong Kong Sci-ence and Technology Innovation Cooperation Zone Shenzhen Park Project(Grant No.HZQB-KCZYB-2020030)the RGC Theme-based Research Scheme(Grant No.AoE/M-402/20)+1 种基金National Nat-ural Science Foundation of China(Grant No.52250710160)Shenzhen Science and Technology Innovation Committee(Grant Nos.KQTD20170328154443162,JCYJ20210324104610029,and JCYJ20220818100613028).
文摘High levels of Al and Ti in superalloy compositions normally lead to cracking formation during the laser powder bed fusion process,while these elements are key constituents of strengthening phases.In the current study,a novel Co-based superalloy with the basic chemical composition of Co-Al-W-Ta-Ti resolved this contradiction,indicating that the part was formed without cracking and simultaneously contained a large amount of strengthening precipitates in the microstructure fabricated via laser powder bed fusion.The printability,microstructures,and mechanical properties of the sample were analysed before and after heat treatment,providing a potential superalloy that can replace Ni-based superalloys fabricated by additive manufacturing in aerospace and other industries with higher temperature and more efficiency.
