Molybdenum carbide has shown great potential in various hydrogenation reactions,and serves as a primary active species for synthesis of ethanol from dimethyl oxalate hydrogenation process which is a crucial step in th...Molybdenum carbide has shown great potential in various hydrogenation reactions,and serves as a primary active species for synthesis of ethanol from dimethyl oxalate hydrogenation process which is a crucial step in the efficient utilization of coal resources.In this study,a molybdenum carbide catalyst with a three-dimensional mesh-like hollow structure and lattice defects was carefully designed.The MoO_(3)precursor with abundant oxygen vacancies and defects was prepared by flame spray pyrolysis,and a structural modifier,Cu,was introduced by sputtering.The Cu deposited by sputtering affected the carburization and phase evolution processes.A three-dimensional mesh-like hollow structure composed of defective molybdenum carbide is formed,with theβ-Mo_(2)C exhibiting lattice distortions and defects.This defectiveβ-Mo_(2)C exhibits high reactivity,and facilitates the C=O hydrogenation process,showing a high reactivity of 83.1%yield in the hydrogenation of dimethyl oxalate.This work provides a new approach to the design and application of molybdenum carbide catalysts.展开更多
In this work,we aim to develop a novel post-treatment process combining cryogenic and pulsed electric field treatment to enhance WC-Co cemented carbides.The results show a 15.62%increase in hardness from 1831.38 to 21...In this work,we aim to develop a novel post-treatment process combining cryogenic and pulsed electric field treatment to enhance WC-Co cemented carbides.The results show a 15.62%increase in hardness from 1831.38 to 2117.38 HV30,a 9.60%rise in fracture toughness from 9.06 to 9.93 MPa·m^(1/2),while the friction coefficient decreases from 0.63 to 0.47.Through the residual stress evolution,WC orientation change and the martensitic transformation of Co,and the internal enhancement mechanism of cryogenic combined with pulsed electric field treatment are revealed.The electron wind generated by the pulsed electric field can efficiently reduce the residual stress induced by cryogenic process.The evolution of residual stress promotes the base slip of WC,increasing the degree of{0001}orientation.In addition,the degree of martensitic transformation of Co intensifies,with the hcp-Co/fcc-Co ratio rising from 0.41%to 17.86%.The enhanced WC{0001}orientation and increased hcp-Co content contribute to significant improvements in hardness and wear resistance.This work provides a novel efficient enhancement strategy for ceramics and alloys,with the potential to be a mainstream strengthening method in the future.展开更多
The high-temperature dissolution behavior of primary carbides in samples taken from GCr15 continuous-casting bloom was observed in-situ by confocal laser scanning microscopy.Equations were fitted to the dissolution ki...The high-temperature dissolution behavior of primary carbides in samples taken from GCr15 continuous-casting bloom was observed in-situ by confocal laser scanning microscopy.Equations were fitted to the dissolution kinetics of primary carbides during either heating or soaking.Dissolution of carbides proceeded in three stages(fast→slow→faster)as either temperature or holding time was increased.During the heating process and during the first and third stages of the soaking process,the original size of the carbides determined the steepness of the slope,but during the middle(“slow”)stage of the soaking process,the slope remained zero.The initial size of the carbides varied greatly,but their final dissolution temperature fell within the narrow range of 1210-1235℃,and the holding time remained within 50 min.Fractal analysis was used to study the morphological characteristics of small and medium-sized carbides during the dissolution process.According to changes in the fractal dimension before and after soaking,the carbides tended to evolve towards a more regular morphology.展开更多
The influence of graphene platelets(GPLs)on the WC grain size of WC-Co-GPLs cemented carbide prepared by low-pressure sintering was investigated.The role of GPLs in refining WC grains was explored by characterizing gr...The influence of graphene platelets(GPLs)on the WC grain size of WC-Co-GPLs cemented carbide prepared by low-pressure sintering was investigated.The role of GPLs in refining WC grains was explored by characterizing grain size and phase distribution.Results show that the addition of GPLs leads to significant grain refinement of WC and the more uniform distribution of WC grain size.When the content of GPLs is 0.10wt%,the average WC grain size in the cemented carbide is 0.39μm,which is 32%lower than that in WC-Co.However,the shape of WC grains is almost unaffected,while the mean free path of Co decreases.The grain refinement of WC is attributed to the homogeneous distribution of GPLs between WC/WC and WC/Co grain boundaries,which hinders the solution and precipitation process of WC in liquid phase Co,as well as the migration and growth of WC grains.Additionally,GPLs can serve as heat transfer plates in materials to improve cooling efficiency,thus inhibiting the growth of WC grain.展开更多
The effects of prior austenite and primary carbides on the mechanical properties of a novel 2.5 GPa grade steel were investigated by treating at various solid-solution temperatures.The ultimate tensile strength and Ch...The effects of prior austenite and primary carbides on the mechanical properties of a novel 2.5 GPa grade steel were investigated by treating at various solid-solution temperatures.The ultimate tensile strength and Charpy U-notch impact energy initially increased and subsequently decreased as the solid-solution temperature rose,while the yield strength consistently decreased.The size of prior austenite grain and martensite block always increased with rising the solid-solution temperature,and austenite grain growth activation energy is 274,969 J/mol.The growth of prior austenite was restricted by primary carbides M6C and MC.The dissolution of the primary carbides not only enhanced solid-solution strengthening and secondary hardening effects but also increased the volume fraction of retained austenite.The increase in the ultimate tensile strength and Charpy U-notch impact energy was primarily attributed to the dissolution of the primary carbides M6C and MC,while the decrease was due to the increase in the size of prior austenite grain and martensite block.Exceptional combination of strength,ductility and toughness with ultimate tensile strength of 2511 MPa,yield strength of 1920 MPa,elongation of 9.5%,reduction of area of 41%and Charpy U-notch impact energy of 19.5 J was obtained when experimental steel was solid-solution treated at 1020℃.展开更多
Tungsten carbide-based(WC-based)cemented carbides are widely recognized as high-performance tool materials.Traditionally,single metals such as cobalt(Co)or nickel(Ni)serve as the binder phase,providing toughness and s...Tungsten carbide-based(WC-based)cemented carbides are widely recognized as high-performance tool materials.Traditionally,single metals such as cobalt(Co)or nickel(Ni)serve as the binder phase,providing toughness and structural integrity.Replacing this phase with high-entropy alloys(HEAs)offers a promising approach to enhancing mechanical properties and addressing sustainability challenges.However,the complex multi-element composition of HEAs complicates conventional experimental design,making it difficult to explore the vast compositional space efficiently.Traditional trial-and-error methods are time-consuming,resource-intensive,and often ineffective in identifying optimal compositions.In contrast,artificial intelligence(AI)-driven approaches enable rapid screening and optimization of alloy compositions,significantly improving predictive accuracy and interpretability.Feature selection techniques were employed to identify key alloying elements influencing hardness,toughness,and wear resistance.To enhance model interpretability,explainable artificial intelligence(XAI)techniques—SHapley Additive exPlanations(SHAP)and Local Interpretable Model-agnostic Explanations(LIME)—were applied to quantify the contributions of individual elements and uncover complex elemental interactions.Furthermore,a high-throughput machine learning(ML)–driven screening approach was implemented to optimize the binder phase composition,facilitating the discovery of HEAs with superiormechanical properties.Experimental validation demonstrated strong agreement between model predictions and measured performance,confirming the reliability of the ML framework.This study underscores the potential of integrating ML and XAI for data-driven materials design,providing a novel strategy for optimizing high-entropy cemented carbides.展开更多
The binder phase performs critically on the comprehensive properties of cemented carbides,especially the hardness(HV)and fracture toughness(K_(IC))relationship.There are strong motivations in both research community a...The binder phase performs critically on the comprehensive properties of cemented carbides,especially the hardness(HV)and fracture toughness(K_(IC))relationship.There are strong motivations in both research community and industry for developing alternative binders to Co in cemented carbide system,due to the reasons such as price instability,property degeneration,and toxicity.Herein,six kinds of high entropy alloys(HEA)including CoCrFeNiMn,CoCrFeMnAl,CoCrFeNiAl,CoCrNiMnAl,CoFeNiMnAl,and CrFeNiMnAl were employed as the alternative binder for the preparation of WC-HEA cemented carbides through mechanical alloying and two-step spark plasma sintering.The impacts of HEA on the microstructures,mechanical properties,and thermal conductivity of WC-HEA hardmetals were determined and discussed.WC-HEA hardmetals exhibited both superior HV and K_(IC)to WC-metal or WC-intermetallic cemented carbides,indicating that HEA alloys were not only harder but also tougher in comparison with traditional metal or intermetallic binders.The HEA bonded hardmetals yielded thermal conductivities much lower than that of traditional WC-Co cemented carbide.The excellent HV-K_(IC)relationship of WC-HEA facilitated the potential engineering structural application of cemented carbides.展开更多
The effect of cerium(Ce)on the solidification microstructure of Cr_(4)Mo_(4)V bearing steel was investigated via a combined experimental and theoretical method.With a trace amount(0.056 wt%)of Ce addition,the coarse c...The effect of cerium(Ce)on the solidification microstructure of Cr_(4)Mo_(4)V bearing steel was investigated via a combined experimental and theoretical method.With a trace amount(0.056 wt%)of Ce addition,the coarse columnar grains in as-cast microstructure transform into equiaxed ones,and the average diameter is reduced from 56 to 27μm.The network-like and bulky primary MC and M2C carbides at the interdendritic regions become disconnected and refined,and their volume percentage decreases from4.15 vol%to 2.1 vol%.Ce-inclusions acting as heterogeneous nucleation agents of prior-austenite grains and Ce atoms segregating at grain boundaries,both contribute to the refinement of grains.Thermodynamic calculations reveal that primary carbides are precipitated afterγ-austenite forms near the end of the solidification process.The modification of primary carbides in size and amount is mainly attributed to the isolated remaining melt separated by refinedγ-austenite grains in which the nucleation of carbides is promoted,while the growth is restrained owing to the less segregation of alloying elements.展开更多
The formation and evolution of M_(6)C carbides in high-W superalloy following solution treatment was investigated at different temperatures.Initially,during solid solution treatment,MC and M_(6)C carbides was precipit...The formation and evolution of M_(6)C carbides in high-W superalloy following solution treatment was investigated at different temperatures.Initially,during solid solution treatment,MC and M_(6)C carbides was precipitated in the alloy.As the temperature increased,the morphology of M_(6)C carbides transitioned from granular to needle-like.During the solution treatment at 1255℃,the MC carbides degraded and transformed into M_(6)C carbides,forming a symbiotic relationship between them.Nonetheless,no clear orientation relationship was observed between the two types of carbides.After further increasing the temperature to 1270℃,the precipitation of needle-like M_(6)C carbides in the dendrite arm was confirmed.This was supported by electron probe X-ray micro-analyzer and selected area electron diffraction patterns.Subsequently,a detailed examination of the three-dimensional morphology and orientation relationship of the needle-like phase with the matrix was carried out using focused-ion-beam and transmission electron microscopy techniques.The results indicated that the flat interface of the needle phase exhibited a specific orientation relationship with the matrix.However,in the three-dimensional plane,the interfaces between the needle-like phase and the matrix were not straight.Furthermore,no clear orientation relationship between the non-straight interfaces and the matrix was observed.As the solution temperature increased,the tensile properties at room temperature progressively decreased,while the stress rupture properties peaked at 1260℃,suggesting that the alloy demonstrated its optimal comprehensive performance at this temperature.A subsequent analysis was conducted on the longitudinal section of the fracture using electron backscattered diffraction.The results showed a noticeable concentration of stress at the interface between MC and M_(6)C carbides,which ultimately led to crack initiation at this interface.In addition,as the solid solution temperature increased,the quantity of symbiotic phases also increased.This phenomenon led to the initiation of cracks at multiple locations,which then propagated and interconnected.As a consequence,the tensile properties and stress rupture life of the alloy progressively deteriorated.展开更多
We review the fundamental properties and significant issues related to Cu/graphite composites.In particular,recent research on the interfacial modification of Cu/graphite composites is addressed,including the metal-mo...We review the fundamental properties and significant issues related to Cu/graphite composites.In particular,recent research on the interfacial modification of Cu/graphite composites is addressed,including the metal-modified layer,carbide-modified layer,and combined modified layer.Additionally,we propose the use of ternary layered carbide as an interface modification layer for Cu/graphite composites.展开更多
In this study, a high-carbon nano-bainitic GCr15Si1Mo bearing steel was investigated. Specifically, the effects of content and size of undissolved carbides on the microstructure and transformation kinetics of nano-bai...In this study, a high-carbon nano-bainitic GCr15Si1Mo bearing steel was investigated. Specifically, the effects of content and size of undissolved carbides on the microstructure and transformation kinetics of nano-bainite were analyzed. The results demonstrated that after prolonged austempering at low temperatures, the mixed microstructure composed of nano-bainite (NB), undissolved carbides (UC), and retained austenite (RA) was obtained in GCr15SiMo steel. When the experimental steel was austenitized at 900 ℃, the undissolved carbides gradually dissolved until reaching a stable state with increasing holding time. Furthermore, at the same austempering temperature, despite different volume fractions of undissolved carbides in the substrate, the volume fractions of nano-bainite in the final microstructures remained essentially the same. Moreover, the higher the content of undissolved carbides in steel, the faster the transformation rate of nano-bainite and the shorter the total transformation time.展开更多
High entropy carbides (HECds) are multi-component carbides consisting of transition metal carbides.HECds are generally composed of five or more metal cations of the equal or near-equal substances,obtaining a single cr...High entropy carbides (HECds) are multi-component carbides consisting of transition metal carbides.HECds are generally composed of five or more metal cations of the equal or near-equal substances,obtaining a single crystal structure.HECds have great potentials for future applications due to excellent mechanical,antioxidant and thermal properties.Due to their complex crystal structures and lattice distortion,computer simulations are widely used to efficiently associate the properties of HECds with the corresponding microstructures.In response to the development of HECds,this article provides an overview of the basic design,preparation process and properties of HECds.展开更多
We investigated the role of metal atomization and solvent decomposition into reductive species and carbon clusters in the phase formation of transition-metal carbides(TMCs;namely,Co_(3)C,Fe_(3)C,TiC,and MoC)by pulsed ...We investigated the role of metal atomization and solvent decomposition into reductive species and carbon clusters in the phase formation of transition-metal carbides(TMCs;namely,Co_(3)C,Fe_(3)C,TiC,and MoC)by pulsed laser ablation of Co,Fe,Ti,and Mo metals in acetone.The interaction between carbon s-p-orbitals and metal d-orbitals causes a redistribution of valence structure through charge transfer,leading to the formation of surface defects as observed by X-ray photoelectron spectroscopy.These defects influence the evolved TMCs,making them effective for hydrogen and oxygen evolution reactions(HER and OER)in an alkaline medium.Co_(3)C with more oxygen affinity promoted CoO(OH)intermediates,and the electrochemical surface oxidation to Co_(3)O_(4)was captured via in situ/operando electrochemical Raman probes,increasing the number of active sites for OER activity.MoC with more d-vacancies exhibits strong hydrogen binding,promoting HER kinetics,whereas Fe_(3)C and TiC with more defect states to trap charge carriers may hinder both OER and HER activities.The results show that the assembled membrane-less electrolyzer with Co_(3)C∥Co_(3)C and MoC∥MoC electrodes requires~2.01 and 1.99 V,respectively,to deliver a 10 mA cm−2 with excellent electrochemical and structural stability.In addition,the ascertained pulsed laser synthesis mechanism and unit-cell packing relations will open up sustainable pathways for obtaining highly stable electrocatalysts for electrolyzers.展开更多
Larger-sized primary carbides lead to stress concentration during the application of H13 hot-work die steel,resulting in microcracks and fatigue failure.Rare earth was usually added to modify the carbides and inclusio...Larger-sized primary carbides lead to stress concentration during the application of H13 hot-work die steel,resulting in microcracks and fatigue failure.Rare earth was usually added to modify the carbides and inclusions.The existing literature is reviewed on the effect of rare earth on primary carbides in H13 steel.A comprehensive review on the effect of rare earth on the characteristics of primary carbides,i.e.,number,size,morphology,and thermal stability in H13 steel,was done.The precipitation mechanism and nucleation of primary carbides with rare earth were summarized.The position and form of rare earth in steel and their effects on alloying elements segregation were reviewed.The addition techniques of rare earth in H13 steel were compared,and the prospects for other uncommon rare earth and emerging technology were present.Based on the current references,it can be known that adding rare earth facilitated refined and dispersed primary carbides.The size of primary carbides would be reduced,and their morphology would be improved because the rare earth inclusions formed in H13 steel can act as nucleation cores forγ-Fe orδ-Fe,refining the dendritic structure.Besides,the number of primary carbides at grain boundaries would be significantly reduced.However,rare earth had little impact on thermal stability.The nucleation of primary carbides tended to be inhibited due to the modification of inclusions by rare earth which were likely to be nucleation cores for primary carbides.Rare earth had been reported to affect the mechanism and process of primary carbide precipitation.Additionally,the addition of rare earth can inhibit the segregation of alloying elements and carbon diffusion by calculation.Thus,laboratory experiments and theoretical calcu-lations need to be conducted to study the states and evolution of rare earth steels.展开更多
The effects of cryogenic treatment(CT)and tempering-cryogenic treatment(TCT)on the microstructure and properties of coarse-grained WC-10Co cemented carbides with different carbon contents were researched.The binder ph...The effects of cryogenic treatment(CT)and tempering-cryogenic treatment(TCT)on the microstructure and properties of coarse-grained WC-10Co cemented carbides with different carbon contents were researched.The binder phase,WC mean grain sizes,W solubility in the binder,relative magnetic s aturation,densities,hardness,wear resistance and second phase precipitation of cemented carbides with different heat treatments were discussed.The results show that there are significant changes of microstructure and properties in the samples with CT and TCT,especially due to the precipitation of metastable nanoparticles W_(x)Co_(y)C_(z) in the binder during the heat treatments of CT and TCT.With the simultaneous combination of microstructure and nanoparticle-reinforced binder,a dramatically improved combination of hardness and wear resistance of the samples after TCT has been achieved.展开更多
The effects of ultrafine WC(WC_(UF),0.5μm) or W(1μm) and C(0.3μm)(W+C)_(UF) additives on the densification,microstructure and mechanical properties of coarse-grained cemented carbides were compared systematically.O...The effects of ultrafine WC(WC_(UF),0.5μm) or W(1μm) and C(0.3μm)(W+C)_(UF) additives on the densification,microstructure and mechanical properties of coarse-grained cemented carbides were compared systematically.Overall,the cemented carbides with WC_(UF)/(W+C)_(UF) additives are almost fully densification to be higher than 99%,and the average grain size is kept above 2.8μm.The WC_(UF) additive assists grains to(truncated)trigonal prism shape by two dimensional(2D) growth,whereas the(W+C)_(UF) additive assists grains to rounded shape by three dimensional(3D) growth,lowers WC contiguity and increases face-centered-cubic Co.The hardness and bending strength of(75WC_(C)-15WC_(UF))-10Co are 86.6 HRA and 2 272 MPa,respectively,both higher than those of(75WC_(C)-15(W+C)_(UF))-10Co,which could be ascribed to the enhanced densification and unblemished grains.However,the fracture toughness of the(75WC_(C)-15(W+C)_(UF))-10Co is 23.5 MPa·m^(1/2),higher than that of the(75WC_(C)-15WC_(UF))-10Co due to the uniform WC-Co structure and flexible binder phase.展开更多
A new ultra-fine tungsten carbide(WC)cemented carbide was fabricated by spark plasma sintering(SPS),in which the CoCrNiCuFe high entropy alloy(HEA)was used as the binder and was mixed with WC carbide through the mecha...A new ultra-fine tungsten carbide(WC)cemented carbide was fabricated by spark plasma sintering(SPS),in which the CoCrNiCuFe high entropy alloy(HEA)was used as the binder and was mixed with WC carbide through the mechanical ball milling method.The microstructure of WC-10 wt%HEA compos-ites was investigated through scanning electron microscopy(SEM),high-resolution transmission electron microscopy(HRTEM),X-ray diffraction(XRD),and differential scanning calorimetry-thermogravimetric analysis(DSC-TG).The results show that the interface characteristics of the WC/HEA system include the FCC(111)//HCP(101^(-)1)interface with stable ionic bonds and the interface that reacts due to the formation of the(Fe,Co)_(3)W_(3)C phase.The mechanical properties of WC-10 wt%HEA composites were investigated through the Vickers hardness test,friction and wear tests,and compression test.The WC-10 wt%HEA composites exhibit good fracture toughness and hardness of 10.98 MPa m^(1/2)and 1988.60 HV30,respec-tively.The compressive strength at room temperature and 800℃is up to 3307 and 1747 MPa,respec-tively.The composites exhibited excellent properties attributed to the good wettability of HEA on WC grains and the consequent strengthening effect on the WC/WC interfaces.展开更多
The production of deep well-shaped WC-Co cemented carbide blocks via industrial powder pressing remains a challenging technical problem,primarily due to the unsuitability of the forming agent.The forming agent paraffi...The production of deep well-shaped WC-Co cemented carbide blocks via industrial powder pressing remains a challenging technical problem,primarily due to the unsuitability of the forming agent.The forming agent paraffin wax was modified through four types of modifiers,including organic high-molecular-mass resins,plasticizers,surfactants and lubricants.The qualitative screening of resin types was explored and an orthogonal experiment involving the combination of these four paraffin wax modifiers was conducted to obtain an optimized quantitative ratio of modifiers.The results reveal that the insertion of the small molecule chain of resin into the interstitial spaces of paraffin wax crystals is likely a crucial factor for improving the compatibility between the resin and paraffin wax.Through orthogonal experiments,the optimized formulation for the forming agent is determined:100 parts of 58#paraffin wax,15 parts of EVA-2,4 parts of DPHP,4 parts of oleic acid amide and 2 parts of stearic acid.This optimized formulation is applied to industrial production at one Chinese company,and qualified deep well-shaped cemented carbide products are achieved,which contain 90wt%WC and 10wt%Co.展开更多
Coarse grained WC-9Co cemented carbides with 0-1.0% TaC(mass fraction) were fabricated by HIP-sintering and gas quenching. The effects of TaC on the microstructures and mechanical properties were investigated using sc...Coarse grained WC-9Co cemented carbides with 0-1.0% TaC(mass fraction) were fabricated by HIP-sintering and gas quenching. The effects of TaC on the microstructures and mechanical properties were investigated using scanning electron microscopy(SEM), energy dispersive X-ray analysis(EDS), X-ray diffractometry(XRD) and mechanical properties tests. The results show that the maximum values of hardness and strength are HV 1124 and 2466 MPa respectively when 0.4% TaC is added. When the content of TaC is more than 0.6%, the grain size of WC is no longer affected by the amount of TaC, and(W,Ta)C occurs as well. Moreover, the strength and fracture toughness increase and the(Ta+W) content decreases with the increase of TaC content. The dependence of(Ta+W) content on the mechanical properties indicates that(Ta+W) content in Co should be decreased as low as possible to improve the mechanical properties of coarse grained WC-TaC-9Co cemented carbides with the microstructure of WC+γ two phase regions.展开更多
Finite dement formulations are used to simulate the evolution of the elastoplastic response of functionally graded cemented carbides （FGCC） due to thermal loading. The geometry of specimens is an axisymmetric solid ...Finite dement formulations are used to simulate the evolution of the elastoplastic response of functionally graded cemented carbides （FGCC） due to thermal loading. The geometry of specimens is an axisymmetric solid cylinder with a two-dimensional gradient. The elastoplastic constitutive relationship is developed by constraint factors. Numerical results show that compressive stresses occur in the surface zone and tensile stresses in the cobalt rich zone when the temperature drops from the initial stress-free temperature of 800 to 0℃. The maximum value of the surface compressive stress is 254 MPa and the maximum value of the tensile stress is 252 MPa in the cobalt rich zones. When the cobalt concentration difference in the specimens is equal to or greater than 0.3, there is pronounced plastic flow in cobalt rich zone. When the temperature heats up from 0 to 800 ℃, the total plastic strain reaches 0.001 4. Plastic flow has a significant effect on the reduction of thermal stress concentration.展开更多
文摘Molybdenum carbide has shown great potential in various hydrogenation reactions,and serves as a primary active species for synthesis of ethanol from dimethyl oxalate hydrogenation process which is a crucial step in the efficient utilization of coal resources.In this study,a molybdenum carbide catalyst with a three-dimensional mesh-like hollow structure and lattice defects was carefully designed.The MoO_(3)precursor with abundant oxygen vacancies and defects was prepared by flame spray pyrolysis,and a structural modifier,Cu,was introduced by sputtering.The Cu deposited by sputtering affected the carburization and phase evolution processes.A three-dimensional mesh-like hollow structure composed of defective molybdenum carbide is formed,with theβ-Mo_(2)C exhibiting lattice distortions and defects.This defectiveβ-Mo_(2)C exhibits high reactivity,and facilitates the C=O hydrogenation process,showing a high reactivity of 83.1%yield in the hydrogenation of dimethyl oxalate.This work provides a new approach to the design and application of molybdenum carbide catalysts.
基金supported by the National Natural Science Foundation of China(Nos.U21A20399 and 52274407)Liaoning Province Applied Basic Research Program(No.2022JH2/101300212).
文摘In this work,we aim to develop a novel post-treatment process combining cryogenic and pulsed electric field treatment to enhance WC-Co cemented carbides.The results show a 15.62%increase in hardness from 1831.38 to 2117.38 HV30,a 9.60%rise in fracture toughness from 9.06 to 9.93 MPa·m^(1/2),while the friction coefficient decreases from 0.63 to 0.47.Through the residual stress evolution,WC orientation change and the martensitic transformation of Co,and the internal enhancement mechanism of cryogenic combined with pulsed electric field treatment are revealed.The electron wind generated by the pulsed electric field can efficiently reduce the residual stress induced by cryogenic process.The evolution of residual stress promotes the base slip of WC,increasing the degree of{0001}orientation.In addition,the degree of martensitic transformation of Co intensifies,with the hcp-Co/fcc-Co ratio rising from 0.41%to 17.86%.The enhanced WC{0001}orientation and increased hcp-Co content contribute to significant improvements in hardness and wear resistance.This work provides a novel efficient enhancement strategy for ceramics and alloys,with the potential to be a mainstream strengthening method in the future.
基金supported by Independent Research Project of State Key Laboratory of Advanced Special Steel,Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University(SKLASS-2023-Z13)the Science and Technology Commission of Shanghai Municipality(No.19DZ2270200)+1 种基金A portion of the work was performed at US National High Magnetic Field Laboratory,which is supported by the National Science Foundation(Cooperative Agreement No.DMR-1157490 and DMR-1644779)the State of Florida.Thanks also to Mary Tyler for editing.
文摘The high-temperature dissolution behavior of primary carbides in samples taken from GCr15 continuous-casting bloom was observed in-situ by confocal laser scanning microscopy.Equations were fitted to the dissolution kinetics of primary carbides during either heating or soaking.Dissolution of carbides proceeded in three stages(fast→slow→faster)as either temperature or holding time was increased.During the heating process and during the first and third stages of the soaking process,the original size of the carbides determined the steepness of the slope,but during the middle(“slow”)stage of the soaking process,the slope remained zero.The initial size of the carbides varied greatly,but their final dissolution temperature fell within the narrow range of 1210-1235℃,and the holding time remained within 50 min.Fractal analysis was used to study the morphological characteristics of small and medium-sized carbides during the dissolution process.According to changes in the fractal dimension before and after soaking,the carbides tended to evolve towards a more regular morphology.
基金National Natural Science Foundation of China(51572224)Guangdong Young Creative Talents(2023KQNCX039)+2 种基金Guangdong Basic and Applied Basic Research Foundation(2023A1515110551)Innovative Team in Higher Educational Institutions of Guangdong Province(2020KCXTD039)2023 Lingnan Normal College Students Innovation and Entrepreneurship Training Program(1742)。
文摘The influence of graphene platelets(GPLs)on the WC grain size of WC-Co-GPLs cemented carbide prepared by low-pressure sintering was investigated.The role of GPLs in refining WC grains was explored by characterizing grain size and phase distribution.Results show that the addition of GPLs leads to significant grain refinement of WC and the more uniform distribution of WC grain size.When the content of GPLs is 0.10wt%,the average WC grain size in the cemented carbide is 0.39μm,which is 32%lower than that in WC-Co.However,the shape of WC grains is almost unaffected,while the mean free path of Co decreases.The grain refinement of WC is attributed to the homogeneous distribution of GPLs between WC/WC and WC/Co grain boundaries,which hinders the solution and precipitation process of WC in liquid phase Co,as well as the migration and growth of WC grains.Additionally,GPLs can serve as heat transfer plates in materials to improve cooling efficiency,thus inhibiting the growth of WC grain.
基金supported financially by National Key Research and Development Program of China(No.2022YFB3705200)Heilongjiang Province's Key Technology Project:‘Leading the Charge with Open Competition’(No.2023ZXJ04A02)Youth Program of CISRI Funding under Grant(No.S-23T60190B).
文摘The effects of prior austenite and primary carbides on the mechanical properties of a novel 2.5 GPa grade steel were investigated by treating at various solid-solution temperatures.The ultimate tensile strength and Charpy U-notch impact energy initially increased and subsequently decreased as the solid-solution temperature rose,while the yield strength consistently decreased.The size of prior austenite grain and martensite block always increased with rising the solid-solution temperature,and austenite grain growth activation energy is 274,969 J/mol.The growth of prior austenite was restricted by primary carbides M6C and MC.The dissolution of the primary carbides not only enhanced solid-solution strengthening and secondary hardening effects but also increased the volume fraction of retained austenite.The increase in the ultimate tensile strength and Charpy U-notch impact energy was primarily attributed to the dissolution of the primary carbides M6C and MC,while the decrease was due to the increase in the size of prior austenite grain and martensite block.Exceptional combination of strength,ductility and toughness with ultimate tensile strength of 2511 MPa,yield strength of 1920 MPa,elongation of 9.5%,reduction of area of 41%and Charpy U-notch impact energy of 19.5 J was obtained when experimental steel was solid-solution treated at 1020℃.
文摘Tungsten carbide-based(WC-based)cemented carbides are widely recognized as high-performance tool materials.Traditionally,single metals such as cobalt(Co)or nickel(Ni)serve as the binder phase,providing toughness and structural integrity.Replacing this phase with high-entropy alloys(HEAs)offers a promising approach to enhancing mechanical properties and addressing sustainability challenges.However,the complex multi-element composition of HEAs complicates conventional experimental design,making it difficult to explore the vast compositional space efficiently.Traditional trial-and-error methods are time-consuming,resource-intensive,and often ineffective in identifying optimal compositions.In contrast,artificial intelligence(AI)-driven approaches enable rapid screening and optimization of alloy compositions,significantly improving predictive accuracy and interpretability.Feature selection techniques were employed to identify key alloying elements influencing hardness,toughness,and wear resistance.To enhance model interpretability,explainable artificial intelligence(XAI)techniques—SHapley Additive exPlanations(SHAP)and Local Interpretable Model-agnostic Explanations(LIME)—were applied to quantify the contributions of individual elements and uncover complex elemental interactions.Furthermore,a high-throughput machine learning(ML)–driven screening approach was implemented to optimize the binder phase composition,facilitating the discovery of HEAs with superiormechanical properties.Experimental validation demonstrated strong agreement between model predictions and measured performance,confirming the reliability of the ML framework.This study underscores the potential of integrating ML and XAI for data-driven materials design,providing a novel strategy for optimizing high-entropy cemented carbides.
基金supported by the National Natural Science Foundation of China(No.52375451)the Shandong Provincial Natural Science Foundation,China(Nos.ZR2023YQ052 and ZR2023ME087)+5 种基金the Shandong Provincial Technological SME Innovation Capability Promotion Project,China(No.2023TSGC0375)the Young Taishan Scholars Program of Shandong Province,China(No.tsqn202306041)the Guangdong Basic and Applied Basic Research Foundation,China(No.2023A1515010044)the Shandong Provincial Youth Innovation Team,China(No.2022KJ038)the Open project of State Key Laboratory of Solid Lubrication,China(No.LSL-22-11)Qilu Youth Scholar Project Funding of Shandong University,China.
文摘The binder phase performs critically on the comprehensive properties of cemented carbides,especially the hardness(HV)and fracture toughness(K_(IC))relationship.There are strong motivations in both research community and industry for developing alternative binders to Co in cemented carbide system,due to the reasons such as price instability,property degeneration,and toxicity.Herein,six kinds of high entropy alloys(HEA)including CoCrFeNiMn,CoCrFeMnAl,CoCrFeNiAl,CoCrNiMnAl,CoFeNiMnAl,and CrFeNiMnAl were employed as the alternative binder for the preparation of WC-HEA cemented carbides through mechanical alloying and two-step spark plasma sintering.The impacts of HEA on the microstructures,mechanical properties,and thermal conductivity of WC-HEA hardmetals were determined and discussed.WC-HEA hardmetals exhibited both superior HV and K_(IC)to WC-metal or WC-intermetallic cemented carbides,indicating that HEA alloys were not only harder but also tougher in comparison with traditional metal or intermetallic binders.The HEA bonded hardmetals yielded thermal conductivities much lower than that of traditional WC-Co cemented carbide.The excellent HV-K_(IC)relationship of WC-HEA facilitated the potential engineering structural application of cemented carbides.
基金Project supported by the National Natural Science Foundation of China(52031013,52173305,52233017)the National Key Research and Development Program(2018YFA0702900)。
文摘The effect of cerium(Ce)on the solidification microstructure of Cr_(4)Mo_(4)V bearing steel was investigated via a combined experimental and theoretical method.With a trace amount(0.056 wt%)of Ce addition,the coarse columnar grains in as-cast microstructure transform into equiaxed ones,and the average diameter is reduced from 56 to 27μm.The network-like and bulky primary MC and M2C carbides at the interdendritic regions become disconnected and refined,and their volume percentage decreases from4.15 vol%to 2.1 vol%.Ce-inclusions acting as heterogeneous nucleation agents of prior-austenite grains and Ce atoms segregating at grain boundaries,both contribute to the refinement of grains.Thermodynamic calculations reveal that primary carbides are precipitated afterγ-austenite forms near the end of the solidification process.The modification of primary carbides in size and amount is mainly attributed to the isolated remaining melt separated by refinedγ-austenite grains in which the nucleation of carbides is promoted,while the growth is restrained owing to the less segregation of alloying elements.
基金support received from the National Key Research and Development Program of China(2022YFB3705000)the National Natural Science Foundation of China(No.52303394)the Liaoning Provincial Natural Science Foundation(No.2023-BS-015).
文摘The formation and evolution of M_(6)C carbides in high-W superalloy following solution treatment was investigated at different temperatures.Initially,during solid solution treatment,MC and M_(6)C carbides was precipitated in the alloy.As the temperature increased,the morphology of M_(6)C carbides transitioned from granular to needle-like.During the solution treatment at 1255℃,the MC carbides degraded and transformed into M_(6)C carbides,forming a symbiotic relationship between them.Nonetheless,no clear orientation relationship was observed between the two types of carbides.After further increasing the temperature to 1270℃,the precipitation of needle-like M_(6)C carbides in the dendrite arm was confirmed.This was supported by electron probe X-ray micro-analyzer and selected area electron diffraction patterns.Subsequently,a detailed examination of the three-dimensional morphology and orientation relationship of the needle-like phase with the matrix was carried out using focused-ion-beam and transmission electron microscopy techniques.The results indicated that the flat interface of the needle phase exhibited a specific orientation relationship with the matrix.However,in the three-dimensional plane,the interfaces between the needle-like phase and the matrix were not straight.Furthermore,no clear orientation relationship between the non-straight interfaces and the matrix was observed.As the solution temperature increased,the tensile properties at room temperature progressively decreased,while the stress rupture properties peaked at 1260℃,suggesting that the alloy demonstrated its optimal comprehensive performance at this temperature.A subsequent analysis was conducted on the longitudinal section of the fracture using electron backscattered diffraction.The results showed a noticeable concentration of stress at the interface between MC and M_(6)C carbides,which ultimately led to crack initiation at this interface.In addition,as the solid solution temperature increased,the quantity of symbiotic phases also increased.This phenomenon led to the initiation of cracks at multiple locations,which then propagated and interconnected.As a consequence,the tensile properties and stress rupture life of the alloy progressively deteriorated.
基金Funded by Changsha Natural Science Foundation(No.kq2208270)。
文摘We review the fundamental properties and significant issues related to Cu/graphite composites.In particular,recent research on the interfacial modification of Cu/graphite composites is addressed,including the metal-modified layer,carbide-modified layer,and combined modified layer.Additionally,we propose the use of ternary layered carbide as an interface modification layer for Cu/graphite composites.
基金support from the National Natural Science Foundation of China(Nos.52001105 and 52122410)the Hebei Natural Science Foundation(Nos.E2022402107,E2023203259 and E2020402101)+1 种基金the Science and Technology Project of Hebei Education Department(No.BJ2021012)the Central Guidance for Local Science and Technology Development Funding Project(No.236Z1021G).
文摘In this study, a high-carbon nano-bainitic GCr15Si1Mo bearing steel was investigated. Specifically, the effects of content and size of undissolved carbides on the microstructure and transformation kinetics of nano-bainite were analyzed. The results demonstrated that after prolonged austempering at low temperatures, the mixed microstructure composed of nano-bainite (NB), undissolved carbides (UC), and retained austenite (RA) was obtained in GCr15SiMo steel. When the experimental steel was austenitized at 900 ℃, the undissolved carbides gradually dissolved until reaching a stable state with increasing holding time. Furthermore, at the same austempering temperature, despite different volume fractions of undissolved carbides in the substrate, the volume fractions of nano-bainite in the final microstructures remained essentially the same. Moreover, the higher the content of undissolved carbides in steel, the faster the transformation rate of nano-bainite and the shorter the total transformation time.
文摘High entropy carbides (HECds) are multi-component carbides consisting of transition metal carbides.HECds are generally composed of five or more metal cations of the equal or near-equal substances,obtaining a single crystal structure.HECds have great potentials for future applications due to excellent mechanical,antioxidant and thermal properties.Due to their complex crystal structures and lattice distortion,computer simulations are widely used to efficiently associate the properties of HECds with the corresponding microstructures.In response to the development of HECds,this article provides an overview of the basic design,preparation process and properties of HECds.
基金National Research Foundation of Korea,Grant/Award Numbers:2019H1D3A1A01071209,2021R1I1A1A01060380,2022R1A2C2010686,2022R1A4A3033528Korea Basic Science Institute,Grant/Award Numbers:2019R1A6C1010042,2021R1A6C103A427。
文摘We investigated the role of metal atomization and solvent decomposition into reductive species and carbon clusters in the phase formation of transition-metal carbides(TMCs;namely,Co_(3)C,Fe_(3)C,TiC,and MoC)by pulsed laser ablation of Co,Fe,Ti,and Mo metals in acetone.The interaction between carbon s-p-orbitals and metal d-orbitals causes a redistribution of valence structure through charge transfer,leading to the formation of surface defects as observed by X-ray photoelectron spectroscopy.These defects influence the evolved TMCs,making them effective for hydrogen and oxygen evolution reactions(HER and OER)in an alkaline medium.Co_(3)C with more oxygen affinity promoted CoO(OH)intermediates,and the electrochemical surface oxidation to Co_(3)O_(4)was captured via in situ/operando electrochemical Raman probes,increasing the number of active sites for OER activity.MoC with more d-vacancies exhibits strong hydrogen binding,promoting HER kinetics,whereas Fe_(3)C and TiC with more defect states to trap charge carriers may hinder both OER and HER activities.The results show that the assembled membrane-less electrolyzer with Co_(3)C∥Co_(3)C and MoC∥MoC electrodes requires~2.01 and 1.99 V,respectively,to deliver a 10 mA cm−2 with excellent electrochemical and structural stability.In addition,the ascertained pulsed laser synthesis mechanism and unit-cell packing relations will open up sustainable pathways for obtaining highly stable electrocatalysts for electrolyzers.
基金supported by the National Natural Science Foundation of China(Grant Nos.52064011 and 52274331)Guizhou Provincial Basic Research Program(Natural Science)(Nos.ZK[2021]258 and ZK[2022]Zhongdian 023)+1 种基金Guizhou Provincial Program on Commercialization of Scientific and Technological Achievements(No.[2022]089)Natural Science Research Project of Guizhou Provincial Department of Education(No.[2022]041).
文摘Larger-sized primary carbides lead to stress concentration during the application of H13 hot-work die steel,resulting in microcracks and fatigue failure.Rare earth was usually added to modify the carbides and inclusions.The existing literature is reviewed on the effect of rare earth on primary carbides in H13 steel.A comprehensive review on the effect of rare earth on the characteristics of primary carbides,i.e.,number,size,morphology,and thermal stability in H13 steel,was done.The precipitation mechanism and nucleation of primary carbides with rare earth were summarized.The position and form of rare earth in steel and their effects on alloying elements segregation were reviewed.The addition techniques of rare earth in H13 steel were compared,and the prospects for other uncommon rare earth and emerging technology were present.Based on the current references,it can be known that adding rare earth facilitated refined and dispersed primary carbides.The size of primary carbides would be reduced,and their morphology would be improved because the rare earth inclusions formed in H13 steel can act as nucleation cores forγ-Fe orδ-Fe,refining the dendritic structure.Besides,the number of primary carbides at grain boundaries would be significantly reduced.However,rare earth had little impact on thermal stability.The nucleation of primary carbides tended to be inhibited due to the modification of inclusions by rare earth which were likely to be nucleation cores for primary carbides.Rare earth had been reported to affect the mechanism and process of primary carbide precipitation.Additionally,the addition of rare earth can inhibit the segregation of alloying elements and carbon diffusion by calculation.Thus,laboratory experiments and theoretical calcu-lations need to be conducted to study the states and evolution of rare earth steels.
基金financially supported by the General Research Institute for Nonferrous Metals Youth Science Foundation(No.52147)。
文摘The effects of cryogenic treatment(CT)and tempering-cryogenic treatment(TCT)on the microstructure and properties of coarse-grained WC-10Co cemented carbides with different carbon contents were researched.The binder phase,WC mean grain sizes,W solubility in the binder,relative magnetic s aturation,densities,hardness,wear resistance and second phase precipitation of cemented carbides with different heat treatments were discussed.The results show that there are significant changes of microstructure and properties in the samples with CT and TCT,especially due to the precipitation of metastable nanoparticles W_(x)Co_(y)C_(z) in the binder during the heat treatments of CT and TCT.With the simultaneous combination of microstructure and nanoparticle-reinforced binder,a dramatically improved combination of hardness and wear resistance of the samples after TCT has been achieved.
基金Funded by the Technology Innovation Leading Program of Shaanxi(No.2022QFY08-02)。
文摘The effects of ultrafine WC(WC_(UF),0.5μm) or W(1μm) and C(0.3μm)(W+C)_(UF) additives on the densification,microstructure and mechanical properties of coarse-grained cemented carbides were compared systematically.Overall,the cemented carbides with WC_(UF)/(W+C)_(UF) additives are almost fully densification to be higher than 99%,and the average grain size is kept above 2.8μm.The WC_(UF) additive assists grains to(truncated)trigonal prism shape by two dimensional(2D) growth,whereas the(W+C)_(UF) additive assists grains to rounded shape by three dimensional(3D) growth,lowers WC contiguity and increases face-centered-cubic Co.The hardness and bending strength of(75WC_(C)-15WC_(UF))-10Co are 86.6 HRA and 2 272 MPa,respectively,both higher than those of(75WC_(C)-15(W+C)_(UF))-10Co,which could be ascribed to the enhanced densification and unblemished grains.However,the fracture toughness of the(75WC_(C)-15(W+C)_(UF))-10Co is 23.5 MPa·m^(1/2),higher than that of the(75WC_(C)-15WC_(UF))-10Co due to the uniform WC-Co structure and flexible binder phase.
基金supported by the Key Program of Scientific Research of Higher Education of Hebei Province(No.ZD2021099)Qinhuangdao Science and Technology Research and Development Plan Project(No.202302B005)+2 种基金National Natural Science Foundation of China(No.52104384)China Postdoctoral Science Foundation(No.2020M683675XB)NSF of Shaanxi Provincial Department of Education(No.21JK0761).
文摘A new ultra-fine tungsten carbide(WC)cemented carbide was fabricated by spark plasma sintering(SPS),in which the CoCrNiCuFe high entropy alloy(HEA)was used as the binder and was mixed with WC carbide through the mechanical ball milling method.The microstructure of WC-10 wt%HEA compos-ites was investigated through scanning electron microscopy(SEM),high-resolution transmission electron microscopy(HRTEM),X-ray diffraction(XRD),and differential scanning calorimetry-thermogravimetric analysis(DSC-TG).The results show that the interface characteristics of the WC/HEA system include the FCC(111)//HCP(101^(-)1)interface with stable ionic bonds and the interface that reacts due to the formation of the(Fe,Co)_(3)W_(3)C phase.The mechanical properties of WC-10 wt%HEA composites were investigated through the Vickers hardness test,friction and wear tests,and compression test.The WC-10 wt%HEA composites exhibit good fracture toughness and hardness of 10.98 MPa m^(1/2)and 1988.60 HV30,respec-tively.The compressive strength at room temperature and 800℃is up to 3307 and 1747 MPa,respec-tively.The composites exhibited excellent properties attributed to the good wettability of HEA on WC grains and the consequent strengthening effect on the WC/WC interfaces.
文摘The production of deep well-shaped WC-Co cemented carbide blocks via industrial powder pressing remains a challenging technical problem,primarily due to the unsuitability of the forming agent.The forming agent paraffin wax was modified through four types of modifiers,including organic high-molecular-mass resins,plasticizers,surfactants and lubricants.The qualitative screening of resin types was explored and an orthogonal experiment involving the combination of these four paraffin wax modifiers was conducted to obtain an optimized quantitative ratio of modifiers.The results reveal that the insertion of the small molecule chain of resin into the interstitial spaces of paraffin wax crystals is likely a crucial factor for improving the compatibility between the resin and paraffin wax.Through orthogonal experiments,the optimized formulation for the forming agent is determined:100 parts of 58#paraffin wax,15 parts of EVA-2,4 parts of DPHP,4 parts of oleic acid amide and 2 parts of stearic acid.This optimized formulation is applied to industrial production at one Chinese company,and qualified deep well-shaped cemented carbide products are achieved,which contain 90wt%WC and 10wt%Co.
基金Project(2013zzts025)supported by the Fundamental Research Funds for the Central Universities of China
文摘Coarse grained WC-9Co cemented carbides with 0-1.0% TaC(mass fraction) were fabricated by HIP-sintering and gas quenching. The effects of TaC on the microstructures and mechanical properties were investigated using scanning electron microscopy(SEM), energy dispersive X-ray analysis(EDS), X-ray diffractometry(XRD) and mechanical properties tests. The results show that the maximum values of hardness and strength are HV 1124 and 2466 MPa respectively when 0.4% TaC is added. When the content of TaC is more than 0.6%, the grain size of WC is no longer affected by the amount of TaC, and(W,Ta)C occurs as well. Moreover, the strength and fracture toughness increase and the(Ta+W) content decreases with the increase of TaC content. The dependence of(Ta+W) content on the mechanical properties indicates that(Ta+W) content in Co should be decreased as low as possible to improve the mechanical properties of coarse grained WC-TaC-9Co cemented carbides with the microstructure of WC+γ two phase regions.
基金The National Natural Science Foundation of China(No.50323008,31070517)Scientific Research Foundation of Guangxi Education Department(No.201203YB097)
文摘Finite dement formulations are used to simulate the evolution of the elastoplastic response of functionally graded cemented carbides （FGCC） due to thermal loading. The geometry of specimens is an axisymmetric solid cylinder with a two-dimensional gradient. The elastoplastic constitutive relationship is developed by constraint factors. Numerical results show that compressive stresses occur in the surface zone and tensile stresses in the cobalt rich zone when the temperature drops from the initial stress-free temperature of 800 to 0℃. The maximum value of the surface compressive stress is 254 MPa and the maximum value of the tensile stress is 252 MPa in the cobalt rich zones. When the cobalt concentration difference in the specimens is equal to or greater than 0.3, there is pronounced plastic flow in cobalt rich zone. When the temperature heats up from 0 to 800 ℃, the total plastic strain reaches 0.001 4. Plastic flow has a significant effect on the reduction of thermal stress concentration.
