This paper proposes a type of double-layer charge liner fabricated using chemical vapor deposition(CVD)that has tungsten as its inner liner.The feasibility of this design was evaluated through penetration tests.Double...This paper proposes a type of double-layer charge liner fabricated using chemical vapor deposition(CVD)that has tungsten as its inner liner.The feasibility of this design was evaluated through penetration tests.Double-layer charge liners were fabricated by using CVD to deposit tungsten layers on the inner surfaces of pure T2 copper liners.The microstructures of the tungsten layers were analyzed using a scanning electron microscope(SEM).The feasibility analysis was carried out by pulsed X-rays,slug-retrieval test and static penetration tests.The shaped charge jet forming and penetration law of inner tungsten-coated double-layer liner were studied by numerical simulation method.The results showed that the double-layer liners could form well-shaped jets.The errors between the X-ray test results and the numerical results were within 11.07%.A slug-retrieval test was found that the retrieved slug was similar to a numerically simulated slug.Compared with the traditional pure copper shaped charge jet,the penetration depth of the double-layer shaped charge liner increased by 11.4% and>10.8% respectively.In summary,the test results are good,and the numerical simulation is in good agreement with the test,which verified the feasibility of using the CVD method to fabricate double-layer charge liners with a high-density and high-strength refractory metal as the inner liner.展开更多
The Mo alloys reinforced by Al2O3 particles were fabricated by hydrothermal synthesis and powder metallurgy. The microstructures of Mo-Al2O3 alloys were studied by using XRD, SEM and TEM. The results show that Al2O3 p...The Mo alloys reinforced by Al2O3 particles were fabricated by hydrothermal synthesis and powder metallurgy. The microstructures of Mo-Al2O3 alloys were studied by using XRD, SEM and TEM. The results show that Al2O3 particles, existing as a stable hexagonal phase(α-Al2O3), are uniformly dispersed in Mo matrix. The ultrafine α-Al2O3 particles remarkably refine grain size and increase dislocation density of Mo alloys. Moreover, a good interfacial bonding zone between α-Al2O3 and Mo grain is obtained. The crystallographic orientations of the interface of the Al2O3 particles and Mo matrix are [111]a-Al2O3//[111]Mo and(112)a-Al2O3//(0 11)Mo. Due to the effect of secondary phase and dislocation strengthening, the yield strength of Mo-2.0 vol.%Al2O3 alloy annealed at 1200 ℃ is approximately 56.0% higher than that of pure Mo. The results confirm that the addition of Al2O3 particles is a promising method to improve the mechanical properties of Mo alloys.展开更多
The inherent difficulty in preservation and processing of conventional red phosphorus flame retardant severely limits its growing applications in polymer materials,thus,there is an urgent need to exploit effective tec...The inherent difficulty in preservation and processing of conventional red phosphorus flame retardant severely limits its growing applications in polymer materials,thus,there is an urgent need to exploit effective technology to modify red phosphorus.Functionalized lignin-based compounds can provide a great potential in improving the preservation and processing of red phosphorus.Here,we prepared melamine modified lignin/aluminum phosphate coated red phosphorus(LMAP@RP)and used it as the flame retardant of acrylonitrile-butadiene-styrene(ABS)resin.With 25wt%loading LMAP@RP,the ABS samples show excellent flame inhibiting capacity and reached UL-94 V-0 rating.Cone calorimetry test results show that the peak heat release rate,total heat release and total smoke release of ABS/25LMAP@RP are reduced strikingly by 64.6%,49.3%,and 30.1%,respectively.The char residue is 15.36wt%and the char layer is continuous and dense.The outstanding flame retardant and smoke-suppressant performances of LMAP@RP show its application prospect for ABS.展开更多
As the interface closest to the edge plasma of a fusion reactor reacting deuterium(D)and tritium(T),plasma-facing material(PFM)need to withstand extreme service conditions with the high particle flux,high heat load,an...As the interface closest to the edge plasma of a fusion reactor reacting deuterium(D)and tritium(T),plasma-facing material(PFM)need to withstand extreme service conditions with the high particle flux,high heat load,and neutrons with energy up to 14.1 MeV.Tungsten(W)is the primary candidate of PFMs in future fusion reactors due to its high melting point,good thermal conductivity,excellent irradiation resistance,and low hydrogen/helium retention.So far,powder metallurgy is a leading route for the preparation of W-based PFM.An alternative approach could be the coating technique,which has advantages on fabricating W PFMs and plasma-facing component(PFC)simultaneously.In the past several years,inspiring results were achieved in the preparation process and performance evaluation of the W coating with high purity,excellent thermal conductivity,and thickness at the millimeter level by atmospheric pressure chemical vapor deposition(APCVD).No obvious grain growth and hardness decrease were observed when the annealing temperature was lower than 1500°C,indicating its good thermal stability.The as-deposited coating exhibited a comparable thermal shock resistance with the conventional W bulk.While the polished sample showed a high crack threshold(0.33-0.44 GW·m^(−2))when exposed to edge localized mode like transient at room temperature,compared to the unpolished counterpart.Irradiation performance of the chemical vapor deposition(CVD)-W exposed to deuterium(D)plasma and fission neutron were also evaluated.Additionally,the practicality of preparation of large-scale W-based PFM by this technique is also demonstrated.This paper gives a short overview on the recent research and development status of the thick W coating prepared by APCVD at Xiamen Tungsten Co.,Ltd and Southwestern Institute of Physics for using as PFM and PFC in fusion devices.展开更多
Extremely high heat flux reaching 20 MW·m^(−2) can be foreseen for the future fusion reactor.Such high heat flux would induce recrystallization of tungsten(W)material,leading to significant strength loss of tungs...Extremely high heat flux reaching 20 MW·m^(−2) can be foreseen for the future fusion reactor.Such high heat flux would induce recrystallization of tungsten(W)material,leading to significant strength loss of tungsten material and increment of ductility at high temperature,in particular when the temperature is much higher than its ductile-to-brittle transition temperature(DBTT).In this paper,an International Thermonuclear Experimental Reactor(ITER)-like tungsten divertor monoblock is modeled,and benchmark has been done first to get consistent results with ITER.Then,the monoblock structure has been optimized in order to get a lowest possible temperature and stress during heating and cooling phase separately compared to the baseline structure.Structural analysis of two kinds of states:stress-relieved tungsten and recrystallized tungsten using finite element method has been performed,aiming at finding out the recrystallization impact on the mechanical behavior of tungsten in divertor monoblock under cyclic high heat flux.Damages due to progressive deformation and time-independent fatigue lifetime of these two states of tungsten have been assessed and compared according to criteria The Structural Design Criteria for ITER In-vessel Components.Finally,the impact of different material recrystallization temperature on mechanical behavior has been explored under stationary heat load.The result shows that after recrystallization,thermal stress of tungsten material can be released by the larger plastic deformation compared to the stress-relieved tungsten.However,it is easier for recrystallized tungsten to get damaged due to progressive deformation as well as fatigue under 20 MW·m^(−2) cyclic heat flux than stress-relieved tungsten because of its relatively lower yield strength and larger plastic strain,which would cause low-cycle strain fatigue.Furthermore,tungsten with lower recrystallization temperature distorts more seriously,and therefore,it can be predicted the cracks would be initiated more easily.展开更多
Samples of ultra-high-purity tungsten prepared using chemical vapour deposition(CVD)technique were irradiated with neutrons at temperatures T_(irr)=373-483 K(stage Ⅱ of defect recovery)and T_(irr)=573-673 K(stage Ⅲ)...Samples of ultra-high-purity tungsten prepared using chemical vapour deposition(CVD)technique were irradiated with neutrons at temperatures T_(irr)=373-483 K(stage Ⅱ of defect recovery)and T_(irr)=573-673 K(stage Ⅲ)up to 0.15 displacements per atom(dpa)in the Belgian reactor(BR2).The study of the microstructure of neutron-damaged samples using transmission electron microscopy(TEM)revealed visible defects with a predominance of dislocation loops.With an increase in the neutron irradiation temperature,the spatial distribution of the loops acquired pronounced inhomogeneity,and their average size moderately increased.Cavities and voids were not observed.Irradiation-induced hardening was found and a linear correlation was obtained between Vickers microhardness and nanohardness for undamaged and neutron-irradiated CVD-W samples.Irradiation of tungsten with neutrons led to a significant increase in the retention of deuterium,which accumulated mainly in vacancy-type traps.Furthermore,the influence of the columnar grain structure in low-dose neutron-irradiated tungsten seemed to be non-trivial upon deuterium retention.展开更多
It is well known that Tb substitution for(Pr,Nd)in(Pr,Nd)-Fe-B based sintered magnetic materials is an effective way to increase intrinsic coercivity,but it is not quite clear whether the increment depends on the diff...It is well known that Tb substitution for(Pr,Nd)in(Pr,Nd)-Fe-B based sintered magnetic materials is an effective way to increase intrinsic coercivity,but it is not quite clear whether the increment depends on the different matrix phases with various doping ingredient or not,which is essential to develop high quality magnets with high coercivity more efficiently and effectively with economic consumption of expensive Tb and other costly heavy rare earths.In this paper,we investigated the efficiency of Tb substitution for magnetic property in(Pr,Nd)-Fe-B sintered permanent magnets by co-doping Ga and Cu elements.It is shown that Ga and Cu co-doping can effectively improve the efficiency of Tb substitution to increase the thermal stability and the coercivity.The intrinsic coercivity increases up to 549 and 987 kA/m respectively by 1.5 wt%and 3.0 wt%Tb substitution in Ga and Cu co-doped magnets while the intrinsic coercivity increases up to only 334 and 613 kA/m respectively by the same amounts of Tb substitution in non-Ga and low-Cu magnets.In other words,it demonstrates that there is about 329-366 kA/m linear equivalent enhancement of intrinsic coercivity by 1.0 wt%Tb substitution for(Pr,Nd)in Ga and Cu co-doped magnets.The temperature coefficients of both intrinsic coercivityβand remanenceαat 20-150℃by 3.0 wt%Tb substitution for the magnets with Ga and Cu co-doping are-0.47%/K and-0.109%/K respectively,and in contrast those values are-0.52%/K and 0.116%/K respectively for the non-Ga and low-Cu magnets.It is the principal reason for more efficient enhancement of magnetic property by Tb substitution in the Ga and Cu co-doped magnets in which Tb atoms are expelled from triple junction phases(TJPs)to penetrate into the grain boundary phases(GB phases)and thus modify the grain boundary.It is prospected that the efficiency of Tb substitution would rely on different matrix phases with various doping constituents.展开更多
The interaction between oxidation and frictional load can greatly deteriorate the performance of ceramic-metal composites.In this work,we used WC-Co cermet as a representative of ceramic-metal composites to study its ...The interaction between oxidation and frictional load can greatly deteriorate the performance of ceramic-metal composites.In this work,we used WC-Co cermet as a representative of ceramic-metal composites to study its wear failure behavior and protection effectiveness.It is found that a transition of wear mechanism from mechanical wear to oxidative wear occurs with increasing temperature.The addition of zirconia can significantly improve the anti-oxidation performance and load-bearing capacity of the cermet under the frictional load.This is mainly attributed to the modulation of the tribo-oxide layer constitutions and changes in surface morphology.The zirconia component facilitates the formation of a dense protective oxide layer and reduces the content of brittle oxides on the worn surface.Based on the understanding of the temperature-and oxidation-induced compositional and microstructural evolutions at the sliding contact surface and subsurface,a promising approach is proposed for developing ceramic-metal composites with high wear resistance and anti-oxidation capability.展开更多
The grain-size dependence of wear resistance of WC-Co cemented carbides(with mean WC grain sizes of 2.2μm,1.6μm,0.8μm and 0.4μm,respectively)was investigated under different tribological conditions.The results sho...The grain-size dependence of wear resistance of WC-Co cemented carbides(with mean WC grain sizes of 2.2μm,1.6μm,0.8μm and 0.4μm,respectively)was investigated under different tribological conditions.The results showed that the grain size had opposite effects on wear resistance of the cemented carbides in dry sliding wear and microabrasion tests.In the former condition,with decrease of WC grain size hence the increase of hardness,plastic deformation,fracture,fragmentation and oxidation were all mitigated,leading to a drastic decrease in the wear rate.In the latter condition,pull-out of WC grains after Co removal dominated the wear,so that the hardness of cemented carbide was not a core factor.As a result,the wear resistance of the cemented carbide generally showed a decreasing trend with decrease of the grain size,except for a slight increase in the ultrafine-grained cemented carbide.Single-pass scratching of the cemented carbides under various loads indicated the same failure mechanism as that in the sliding wear tests.Furthermore,the reasons for severe surface oxidation of the coarse-grained cemented carbides were disclosed.展开更多
Hardmetals are tungsten carbide(WC)-based composites,which are made of WC as a hard phase and transition metals such as Co,Fe,or/and Ni as ductile binder matrices.Their properties can be mainly tailored through the gr...Hardmetals are tungsten carbide(WC)-based composites,which are made of WC as a hard phase and transition metals such as Co,Fe,or/and Ni as ductile binder matrices.Their properties can be mainly tailored through the grain sizes of the sintered carbides and the amount of metallic binder.As successful tool materials,hardmetals are widely applied in metal cutting,wear applications,chipless forming,stoneworking,wood,and plastic working.In 2017,about two-thirds of tungsten consumption(including recycled materials)were produced for hardmetals in the world.This paper briefly introduces the development of manufacturing technology on WC-Co hardmetals from three aspects:powder preparation,bulk densifica-tion,and performance characterization.Two special WC-Co hardmetals are also described:cobalt-enrichment zone(CEZ)hardmetals,and binderless hardmetals.Furthermore,the development prospects for manufacturing techniques of hardmetals are also presented in the end.展开更多
基金funded by the China Postdoctoral Science Foundation(Grant No.2022M721614)the opening project of State Key Laboratory of Explosion Science and Technology,Beijing Institute of Technology(Grant No.KFJJ23-07M)。
文摘This paper proposes a type of double-layer charge liner fabricated using chemical vapor deposition(CVD)that has tungsten as its inner liner.The feasibility of this design was evaluated through penetration tests.Double-layer charge liners were fabricated by using CVD to deposit tungsten layers on the inner surfaces of pure T2 copper liners.The microstructures of the tungsten layers were analyzed using a scanning electron microscope(SEM).The feasibility analysis was carried out by pulsed X-rays,slug-retrieval test and static penetration tests.The shaped charge jet forming and penetration law of inner tungsten-coated double-layer liner were studied by numerical simulation method.The results showed that the double-layer liners could form well-shaped jets.The errors between the X-ray test results and the numerical results were within 11.07%.A slug-retrieval test was found that the retrieved slug was similar to a numerically simulated slug.Compared with the traditional pure copper shaped charge jet,the penetration depth of the double-layer shaped charge liner increased by 11.4% and>10.8% respectively.In summary,the test results are good,and the numerical simulation is in good agreement with the test,which verified the feasibility of using the CVD method to fabricate double-layer charge liners with a high-density and high-strength refractory metal as the inner liner.
基金Projects(U1704152,U1804124)supported by the National Natural Science Foundation of ChinaProject(174100510012)supported by Plan for Scientific Innovation Talent of Henan Province,China。
文摘The Mo alloys reinforced by Al2O3 particles were fabricated by hydrothermal synthesis and powder metallurgy. The microstructures of Mo-Al2O3 alloys were studied by using XRD, SEM and TEM. The results show that Al2O3 particles, existing as a stable hexagonal phase(α-Al2O3), are uniformly dispersed in Mo matrix. The ultrafine α-Al2O3 particles remarkably refine grain size and increase dislocation density of Mo alloys. Moreover, a good interfacial bonding zone between α-Al2O3 and Mo grain is obtained. The crystallographic orientations of the interface of the Al2O3 particles and Mo matrix are [111]a-Al2O3//[111]Mo and(112)a-Al2O3//(0 11)Mo. Due to the effect of secondary phase and dislocation strengthening, the yield strength of Mo-2.0 vol.%Al2O3 alloy annealed at 1200 ℃ is approximately 56.0% higher than that of pure Mo. The results confirm that the addition of Al2O3 particles is a promising method to improve the mechanical properties of Mo alloys.
基金Funded by the National Natural Science Foundation of China(No.51503041)the Natural Science Foundation of Fujian Province,China(No.2018J01752)。
文摘The inherent difficulty in preservation and processing of conventional red phosphorus flame retardant severely limits its growing applications in polymer materials,thus,there is an urgent need to exploit effective technology to modify red phosphorus.Functionalized lignin-based compounds can provide a great potential in improving the preservation and processing of red phosphorus.Here,we prepared melamine modified lignin/aluminum phosphate coated red phosphorus(LMAP@RP)and used it as the flame retardant of acrylonitrile-butadiene-styrene(ABS)resin.With 25wt%loading LMAP@RP,the ABS samples show excellent flame inhibiting capacity and reached UL-94 V-0 rating.Cone calorimetry test results show that the peak heat release rate,total heat release and total smoke release of ABS/25LMAP@RP are reduced strikingly by 64.6%,49.3%,and 30.1%,respectively.The char residue is 15.36wt%and the char layer is continuous and dense.The outstanding flame retardant and smoke-suppressant performances of LMAP@RP show its application prospect for ABS.
基金This work is financially supported by the National Magnetic Confinement Fusion Program of China(Grant No.2018YFE0312100)the National Natural Science Foundation of China(Grant Nos.11975092 and 11905045).
文摘As the interface closest to the edge plasma of a fusion reactor reacting deuterium(D)and tritium(T),plasma-facing material(PFM)need to withstand extreme service conditions with the high particle flux,high heat load,and neutrons with energy up to 14.1 MeV.Tungsten(W)is the primary candidate of PFMs in future fusion reactors due to its high melting point,good thermal conductivity,excellent irradiation resistance,and low hydrogen/helium retention.So far,powder metallurgy is a leading route for the preparation of W-based PFM.An alternative approach could be the coating technique,which has advantages on fabricating W PFMs and plasma-facing component(PFC)simultaneously.In the past several years,inspiring results were achieved in the preparation process and performance evaluation of the W coating with high purity,excellent thermal conductivity,and thickness at the millimeter level by atmospheric pressure chemical vapor deposition(APCVD).No obvious grain growth and hardness decrease were observed when the annealing temperature was lower than 1500°C,indicating its good thermal stability.The as-deposited coating exhibited a comparable thermal shock resistance with the conventional W bulk.While the polished sample showed a high crack threshold(0.33-0.44 GW·m^(−2))when exposed to edge localized mode like transient at room temperature,compared to the unpolished counterpart.Irradiation performance of the chemical vapor deposition(CVD)-W exposed to deuterium(D)plasma and fission neutron were also evaluated.Additionally,the practicality of preparation of large-scale W-based PFM by this technique is also demonstrated.This paper gives a short overview on the recent research and development status of the thick W coating prepared by APCVD at Xiamen Tungsten Co.,Ltd and Southwestern Institute of Physics for using as PFM and PFC in fusion devices.
基金This work was financially supported by the National Natural Science Foundation of China(Grant No.11975092)National Magnetic Confinement Fusion Program of China(Grant Nos.2018YFE0312100 and 2019YFE03120003).
文摘Extremely high heat flux reaching 20 MW·m^(−2) can be foreseen for the future fusion reactor.Such high heat flux would induce recrystallization of tungsten(W)material,leading to significant strength loss of tungsten material and increment of ductility at high temperature,in particular when the temperature is much higher than its ductile-to-brittle transition temperature(DBTT).In this paper,an International Thermonuclear Experimental Reactor(ITER)-like tungsten divertor monoblock is modeled,and benchmark has been done first to get consistent results with ITER.Then,the monoblock structure has been optimized in order to get a lowest possible temperature and stress during heating and cooling phase separately compared to the baseline structure.Structural analysis of two kinds of states:stress-relieved tungsten and recrystallized tungsten using finite element method has been performed,aiming at finding out the recrystallization impact on the mechanical behavior of tungsten in divertor monoblock under cyclic high heat flux.Damages due to progressive deformation and time-independent fatigue lifetime of these two states of tungsten have been assessed and compared according to criteria The Structural Design Criteria for ITER In-vessel Components.Finally,the impact of different material recrystallization temperature on mechanical behavior has been explored under stationary heat load.The result shows that after recrystallization,thermal stress of tungsten material can be released by the larger plastic deformation compared to the stress-relieved tungsten.However,it is easier for recrystallized tungsten to get damaged due to progressive deformation as well as fatigue under 20 MW·m^(−2) cyclic heat flux than stress-relieved tungsten because of its relatively lower yield strength and larger plastic strain,which would cause low-cycle strain fatigue.Furthermore,tungsten with lower recrystallization temperature distorts more seriously,and therefore,it can be predicted the cracks would be initiated more easily.
基金Neutron irradiations at BR2 in SCK/CEN were carried out in the framework of MICADO project.Hot-lab experiments were conducted at the International Research Centre for Nuclear Materials Science(Oarai site),Institute for Materials Research(IMR),Tohoku University.All authors wish to thank IMR staffs Mr.K.Suzuki and T.Maniwa for their kind assistance.X.Yi acknowledges funding support from the Global Institute for Materials Research Tohoku(GIMRT)program via proposals No.19M0504,20M0502 and 202012-IRKMA-0516the National Natural Science Foundation of China via grant No.12175013J.P.Song acknowledges funding support from the National Magnetic Confinement Fusion Program of China via Grant No.2018YFE031210.
文摘Samples of ultra-high-purity tungsten prepared using chemical vapour deposition(CVD)technique were irradiated with neutrons at temperatures T_(irr)=373-483 K(stage Ⅱ of defect recovery)and T_(irr)=573-673 K(stage Ⅲ)up to 0.15 displacements per atom(dpa)in the Belgian reactor(BR2).The study of the microstructure of neutron-damaged samples using transmission electron microscopy(TEM)revealed visible defects with a predominance of dislocation loops.With an increase in the neutron irradiation temperature,the spatial distribution of the loops acquired pronounced inhomogeneity,and their average size moderately increased.Cavities and voids were not observed.Irradiation-induced hardening was found and a linear correlation was obtained between Vickers microhardness and nanohardness for undamaged and neutron-irradiated CVD-W samples.Irradiation of tungsten with neutrons led to a significant increase in the retention of deuterium,which accumulated mainly in vacancy-type traps.Furthermore,the influence of the columnar grain structure in low-dose neutron-irradiated tungsten seemed to be non-trivial upon deuterium retention.
基金Project supported by the National Natural Science Foundation of China(51901089,52061015)Young Elite Scientists Sponsorship Program by CAST(YESS20200250)+3 种基金Young Talents Program of Jiangxi Provincial Major Discipline Academic and Technical Leaders Training Program(20212BCJ23008)China Postdoctoral Science Foundation(2020M682064)Postdoctoral Science foundation of Jiangxi Province(2020KY19)Technology Program of Fujian Province(2020H6201,2021T3063)。
文摘It is well known that Tb substitution for(Pr,Nd)in(Pr,Nd)-Fe-B based sintered magnetic materials is an effective way to increase intrinsic coercivity,but it is not quite clear whether the increment depends on the different matrix phases with various doping ingredient or not,which is essential to develop high quality magnets with high coercivity more efficiently and effectively with economic consumption of expensive Tb and other costly heavy rare earths.In this paper,we investigated the efficiency of Tb substitution for magnetic property in(Pr,Nd)-Fe-B sintered permanent magnets by co-doping Ga and Cu elements.It is shown that Ga and Cu co-doping can effectively improve the efficiency of Tb substitution to increase the thermal stability and the coercivity.The intrinsic coercivity increases up to 549 and 987 kA/m respectively by 1.5 wt%and 3.0 wt%Tb substitution in Ga and Cu co-doped magnets while the intrinsic coercivity increases up to only 334 and 613 kA/m respectively by the same amounts of Tb substitution in non-Ga and low-Cu magnets.In other words,it demonstrates that there is about 329-366 kA/m linear equivalent enhancement of intrinsic coercivity by 1.0 wt%Tb substitution for(Pr,Nd)in Ga and Cu co-doped magnets.The temperature coefficients of both intrinsic coercivityβand remanenceαat 20-150℃by 3.0 wt%Tb substitution for the magnets with Ga and Cu co-doping are-0.47%/K and-0.109%/K respectively,and in contrast those values are-0.52%/K and 0.116%/K respectively for the non-Ga and low-Cu magnets.It is the principal reason for more efficient enhancement of magnetic property by Tb substitution in the Ga and Cu co-doped magnets in which Tb atoms are expelled from triple junction phases(TJPs)to penetrate into the grain boundary phases(GB phases)and thus modify the grain boundary.It is prospected that the efficiency of Tb substitution would rely on different matrix phases with various doping constituents.
基金supported by the Beijing Natural Science Foundation(No.2222046)the National Natural Science Foundation of China(Nos.92163107,52101003,52171061,and U20A20236)+1 种基金the National Key R&D Program of China(Nos.2021YFB3501502 and 2021YFB3501504),Haihe Laboratory in Tianjin(No.22HHXCJC00007)the International Research Cooperation Seed Fund of Beijing University of Technology(No.20211222).
文摘The interaction between oxidation and frictional load can greatly deteriorate the performance of ceramic-metal composites.In this work,we used WC-Co cermet as a representative of ceramic-metal composites to study its wear failure behavior and protection effectiveness.It is found that a transition of wear mechanism from mechanical wear to oxidative wear occurs with increasing temperature.The addition of zirconia can significantly improve the anti-oxidation performance and load-bearing capacity of the cermet under the frictional load.This is mainly attributed to the modulation of the tribo-oxide layer constitutions and changes in surface morphology.The zirconia component facilitates the formation of a dense protective oxide layer and reduces the content of brittle oxides on the worn surface.Based on the understanding of the temperature-and oxidation-induced compositional and microstructural evolutions at the sliding contact surface and subsurface,a promising approach is proposed for developing ceramic-metal composites with high wear resistance and anti-oxidation capability.
基金supported financially by the National Natural Science Foundation of China (Nos.51601004,51631002,51425101 and 51621003)the China Scholarship Council (201806545002)the Program of Top Disciplines Construction in Beijing (No. PXM2019_014204_500031)
文摘The grain-size dependence of wear resistance of WC-Co cemented carbides(with mean WC grain sizes of 2.2μm,1.6μm,0.8μm and 0.4μm,respectively)was investigated under different tribological conditions.The results showed that the grain size had opposite effects on wear resistance of the cemented carbides in dry sliding wear and microabrasion tests.In the former condition,with decrease of WC grain size hence the increase of hardness,plastic deformation,fracture,fragmentation and oxidation were all mitigated,leading to a drastic decrease in the wear rate.In the latter condition,pull-out of WC grains after Co removal dominated the wear,so that the hardness of cemented carbide was not a core factor.As a result,the wear resistance of the cemented carbide generally showed a decreasing trend with decrease of the grain size,except for a slight increase in the ultrafine-grained cemented carbide.Single-pass scratching of the cemented carbides under various loads indicated the same failure mechanism as that in the sliding wear tests.Furthermore,the reasons for severe surface oxidation of the coarse-grained cemented carbides were disclosed.
基金the Major Special Projects of Fujian Science and Technology Plan(Grant No.2017HZ0001-1)。
文摘Hardmetals are tungsten carbide(WC)-based composites,which are made of WC as a hard phase and transition metals such as Co,Fe,or/and Ni as ductile binder matrices.Their properties can be mainly tailored through the grain sizes of the sintered carbides and the amount of metallic binder.As successful tool materials,hardmetals are widely applied in metal cutting,wear applications,chipless forming,stoneworking,wood,and plastic working.In 2017,about two-thirds of tungsten consumption(including recycled materials)were produced for hardmetals in the world.This paper briefly introduces the development of manufacturing technology on WC-Co hardmetals from three aspects:powder preparation,bulk densifica-tion,and performance characterization.Two special WC-Co hardmetals are also described:cobalt-enrichment zone(CEZ)hardmetals,and binderless hardmetals.Furthermore,the development prospects for manufacturing techniques of hardmetals are also presented in the end.
